The get_time() callbacks always need to match the bases clockid.
Instead of maintaining that association twice in hrtimer_bases,
use a helper.
Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/all/20250821-hrtimer-cleanup-get_time-v2-8-3ae822e5bfbd@linutronix.de
The field timer->base->get_time is a private implementation detail and
should not be accessed outside of the hrtimer core.
Switch to the equivalent helper.
Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/all/20250821-hrtimer-cleanup-get_time-v2-2-3ae822e5bfbd@linutronix.de
The field timer->base->get_time is a private implementation detail and
should not be accessed outside of the hrtimer core.
Switch to the equivalent helpers.
Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/all/20250821-hrtimer-cleanup-get_time-v2-1-3ae822e5bfbd@linutronix.de
The generic vDSO can be used without the time-related functionality.
In that case the generic update_vsyscall() from kernel/time/vsyscall.c
should not be built.
Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/20250826-vdso-cleanups-v1-5-d9b65750e49f@linutronix.de
Export the timespec64_add_safe() symbol so that this function can be used
in modules where computation of time related is done.
Signed-off-by: Gatien Chevallier <gatien.chevallier@foss.st.com>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://patch.msgid.link/20250901-relative_flex_pps-v4-1-b874971dfe85@foss.st.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
The call to __iter_div_u64_rem() in vdso_time_update_aux() is a wrapper
around subtraction. It cannot be used to divide large numbers, as that
introduces long, computationally expensive delays. A regular u64 division
is also not possible in the timekeeper update path as it can be too slow.
Instead of splitting the ktime_t offset into into second and subsecond
components during the timekeeper update fast-path, do it together with the
adjustment of tk->offs_aux in the slow-path. Equivalent to the handling of
offs_boot and monotonic_to_boot.
Reuse the storage of monotonic_to_boot for the new field, as it is not used
by auxiliary timekeepers.
Fixes: 380b84e168 ("vdso/vsyscall: Update auxiliary clock data in the datapage")
Reported-by: Miroslav Lichvar <mlichvar@redhat.com>
Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/20250825-vdso-auxclock-division-v1-1-a1d32a16a313@linutronix.de
Closes: https://lore.kernel.org/lkml/aKwsNNWsHJg8IKzj@localhost/
With the introduction of clone3 in commit 7f192e3cd3 ("fork: add
clone3") the effective bit width of clone_flags on all architectures was
increased from 32-bit to 64-bit, with a new type of u64 for the flags.
However, for most consumers of clone_flags the interface was not
changed from the previous type of unsigned long.
While this works fine as long as none of the new 64-bit flag bits
(CLONE_CLEAR_SIGHAND and CLONE_INTO_CGROUP) are evaluated, this is still
undesirable in terms of the principle of least surprise.
Thus, this commit fixes all relevant interfaces of callees to
sys_clone3/copy_process (excluding the architecture-specific
copy_thread) to consistently pass clone_flags as u64, so that
no truncation to 32-bit integers occurs on 32-bit architectures.
Signed-off-by: Simon Schuster <schuster.simon@siemens-energy.com>
Link: https://lore.kernel.org/20250901-nios2-implement-clone3-v2-2-53fcf5577d57@siemens-energy.com
Acked-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Christian Brauner <brauner@kernel.org>
The current algorithm of picking a random CPU works OK for dense online
cpumask, but if cpumask is non-dense, the distribution of picked CPUs
is skewed.
For example, on 8-CPU board with CPUs 4-7 offlined, the probability of
selecting CPU 0 is 5/8. Accordingly, cpus 1, 2 and 3 are chosen with
probability 1/8 each. The proper algorithm should pick each online CPU
with probability 1/4.
Switch it to cpumask_random(), which has better statistical
characteristics.
CC: Andrew Morton <akpm@linux-foundation.org>
Acked-by: John Stultz <jstultz@google.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: "Yury Norov [NVIDIA]" <yury.norov@gmail.com>
- Introduce support for auxiliary timekeepers
PTP clocks can be disconnected from the universal CLOCK_TAI reality
for various reasons including regularatory requirements for
functional safety redundancy.
The kernel so far only supports a single notion of time, which means
that all clocks are correlated in frequency and only differ by
offset to each other.
Access to non-correlated PTP clocks has been available so far only
through the file descriptor based "POSIX clock IDs", which are
subject to locking and have to go all the way out to the hardware.
The access is not only horribly slow, as it has to go all the way out
to the NIC/PTP hardware, but that also prevents the kernel to read
the time of such clocks e.g. from the network stack, where it is
required for TSN networking both on the transmit and receive side
unless the hardware provides offloading.
The auxiliary clocks provide a mechanism to support arbitrary clocks
which are not correlated to the system clock. This is not restricted
to the PTP use case on purpose as there is no kernel side association
of these clocks to a particular PTP device because that's a pure user
space configuration decision. Having them independent allows to
utilize them for other purposes and also enables them to be tested
without hardware dependencies.
To avoid pointless overhead these clocks have to be enabled
individualy via a new sysfs interface to reduce the overhead to a
single compare in the hotpath if they are enabled at the Kconfig
level at all.
These clocks utilize the existing timekeeping/NTP infrastructures,
which has been made possible over the recent releases by incrementaly
converting these infrastructures over from a single static instance
to a multi-instance pointer based implementation without any
performance regression reported.
The auxiliary clocks provide the same "emulation" of a "correct"
clock as the existing CLOCK_* variants do with an independent
instance of data and provide the same steering mechanism through the
existing sys_clock_adjtime() interface, which has been confirmed to
work by the chronyd(8) maintainer.
That allows to provide lockless kernel internal and VDSO support so
that applications and kernel internal functionalities can access
these clocks without restrictions and at the same performance as the
existing system clocks.
- Avoid double notifications in the adjtimex() syscall. Not a big issue,
but a trivial to avoid latency source.
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Merge tag 'timers-ptp-2025-07-27' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull timekeeping and VDSO updates from Thomas Gleixner:
- Introduce support for auxiliary timekeepers
PTP clocks can be disconnected from the universal CLOCK_TAI reality
for various reasons including regularatory requirements for
functional safety redundancy.
The kernel so far only supports a single notion of time, which means
that all clocks are correlated in frequency and only differ by offset
to each other.
Access to non-correlated PTP clocks has been available so far only
through the file descriptor based "POSIX clock IDs", which are
subject to locking and have to go all the way out to the hardware.
The access is not only horribly slow, as it has to go all the way out
to the NIC/PTP hardware, but that also prevents the kernel to read
the time of such clocks e.g. from the network stack, where it is
required for TSN networking both on the transmit and receive side
unless the hardware provides offloading.
The auxiliary clocks provide a mechanism to support arbitrary clocks
which are not correlated to the system clock. This is not restricted
to the PTP use case on purpose as there is no kernel side association
of these clocks to a particular PTP device because that's a pure user
space configuration decision. Having them independent allows to
utilize them for other purposes and also enables them to be tested
without hardware dependencies.
To avoid pointless overhead these clocks have to be enabled
individualy via a new sysfs interface to reduce the overhead to a
single compare in the hotpath if they are enabled at the Kconfig
level at all.
These clocks utilize the existing timekeeping/NTP infrastructures,
which has been made possible over the recent releases by incrementaly
converting these infrastructures over from a single static instance
to a multi-instance pointer based implementation without any
performance regression reported.
The auxiliary clocks provide the same "emulation" of a "correct"
clock as the existing CLOCK_* variants do with an independent
instance of data and provide the same steering mechanism through the
existing sys_clock_adjtime() interface, which has been confirmed to
work by the chronyd(8) maintainer.
That allows to provide lockless kernel internal and VDSO support so
that applications and kernel internal functionalities can access
these clocks without restrictions and at the same performance as the
existing system clocks.
- Avoid double notifications in the adjtimex() syscall. Not a big
issue, but a trivial to avoid latency source.
* tag 'timers-ptp-2025-07-27' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (39 commits)
vdso/gettimeofday: Add support for auxiliary clocks
vdso/vsyscall: Update auxiliary clock data in the datapage
vdso: Introduce aux_clock_resolution_ns()
vdso/gettimeofday: Introduce vdso_get_timestamp()
vdso/gettimeofday: Introduce vdso_set_timespec()
vdso/gettimeofday: Introduce vdso_clockid_valid()
vdso/gettimeofday: Return bool from clock_gettime() helpers
vdso/gettimeofday: Return bool from clock_getres() helpers
vdso/helpers: Add helpers for seqlocks of single vdso_clock
vdso/vsyscall: Split up __arch_update_vsyscall() into __arch_update_vdso_clock()
vdso/vsyscall: Introduce a helper to fill clock configurations
timekeeping: Remove the temporary CLOCK_AUX workaround
timekeeping: Provide ktime_get_clock_ts64()
timekeeping: Provide interface to control auxiliary clocks
timekeeping: Provide update for auxiliary timekeepers
timekeeping: Provide adjtimex() for auxiliary clocks
timekeeping: Prepare do_adtimex() for auxiliary clocks
timekeeping: Make do_adjtimex() reusable
timekeeping: Add auxiliary clock support to __timekeeping_inject_offset()
timekeeping: Make timekeeping_inject_offset() reusable
...
- Simplify the logic in the timer migration code
- Simplify the clocksource code by utilizing the more modern cpumask+*()
interfaces
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Merge tag 'timers-core-2025-07-27' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull timer core updates from Thomas Gleixner:
- Simplify the logic in the timer migration code
- Simplify the clocksource code by utilizing the more modern
cpumask+*() interfaces
* tag 'timers-core-2025-07-27' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
clocksource: Use cpumask_next_wrap() in clocksource_watchdog()
clocksource: Use cpumask_any_but() in clocksource_verify_choose_cpus()
timers/migration: Clean up the loop in tmigr_quick_check()
The initial idea of making them const was correct as they were seperate
instances. When they got embedded into larger data structures, which are
even modified by the callback this got moot. The only reason why this went
unnoticed is that the required container_of() casts the const attribute
forcefully away.
Stop pretending that it is const.
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Merge tag 'timers-cleanups-2025-07-27' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull timer cleanups from Thomas Gleixner:
"A treewide cleanup of struct cycle_counter const annotations.
The initial idea of making them const was correct as they were
seperate instances. When they got embedded into larger data
structures, which are even modified by the callback this got moot. The
only reason why this went unnoticed is that the required
container_of() casts the const attribute forcefully away.
Stop pretending that it is const"
* tag 'timers-cleanups-2025-07-27' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
time/timecounter: Fix the lie that struct cyclecounter is const
Most drivers only populate the fields cycles and cs_id of system_counterval
in their get_time_fn() callback for get_device_system_crosststamp(), unless
they explicitly provide nanosecond values.
When the use_nsecs field was added to struct system_counterval, most
drivers did not care. Clock sources other than CSID_GENERIC could then get
converted in convert_base_to_cs() based on an uninitialized use_nsecs field,
which usually results in -EINVAL during the following range check.
Pass in a fully zero initialized system_counterval_t to cure that.
Fixes: 6b2e299775 ("timekeeping: Provide infrastructure for converting to/from a base clock")
Signed-off-by: Markus Blöchl <markus@blochl.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: John Stultz <jstultz@google.com>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/all/20250720-timekeeping_uninit_crossts-v2-1-f513c885b7c2@blochl.de
Expose the auxiliary clock data so it can be read from the vDSO.
Architectures not using the generic vDSO time framework,
namely SPARC64, are not supported.
Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/20250701-vdso-auxclock-v1-11-df7d9f87b9b8@linutronix.de
The upcoming auxiliary clocks need this hook, too.
To separate the architecture hooks from the timekeeper internals, refactor
the hook to only operate on a single vDSO clock.
While at it, use a more robust #define for the hook override.
Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/20250701-vdso-auxclock-v1-3-df7d9f87b9b8@linutronix.de
The logic to configure a 'struct vdso_clock' from a
'struct tk_read_base' is copied two times.
Split it into a shared function to reduce the duplication,
especially as another user will be added for auxiliary clocks.
Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/20250701-vdso-auxclock-v1-2-df7d9f87b9b8@linutronix.de
allow integration of depending changes into the networking tree.
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Merge tag 'ktime-get-clock-ts64-for-ptp' into timers/ptp
Pull the base implementation of ktime_get_clock_ts64() for PTP, which
contains a temporary CLOCK_AUX* workaround. That was created to allow
integration of depending changes into the networking tree. The workaround
is going to be removed in a subsequent change in the timekeeping tree.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
PTP implements an inline switch case for taking timestamps from various
POSIX clock IDs, which already consumes quite some text space. Expanding it
for auxiliary clocks really becomes too big for inlining.
Provide a out of line version.
The function invalidates the timestamp in case the clock is invalid. The
invalidation allows to implement a validation check without the need to
propagate a return value through deep existing call chains.
Due to merge logistics this temporarily defines CLOCK_AUX[_LAST] if
undefined, so that the plain branch, which does not contain any of the core
timekeeper changes, can be pulled into the networking tree as prerequisite
for the PTP side changes. These temporary defines are removed after that
branch is merged into the tip::timers/ptp branch. That way the result in
-next or upstream in the next merge window has zero dependencies.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Vadim Fedorenko <vadim.fedorenko@linux.dev>
Acked-by: John Stultz <jstultz@google.com>
Link: https://lore.kernel.org/all/20250701132628.357686408@linutronix.de
In both the read callback for struct cyclecounter, and in struct
timecounter, struct cyclecounter is declared as a const pointer.
Unfortunatly, a number of users of this pointer treat it as a non-const
pointer as it is burried in a larger structure that is heavily modified by
the callback function when accessed. This lie had been hidden by the fact
that container_of() "casts away" a const attribute of a pointer without any
compiler warning happening at all.
Fix this all up by removing the const attribute in the needed places so
that everyone can see that the structure really isn't const, but can,
and is, modified by the users of it.
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/2025070124-backyard-hurt-783a@gregkh
Auxiliary clocks are disabled by default and attempts to access them
fail.
Provide an interface to enable/disable them at run-time.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: John Stultz <jstultz@google.com>
Link: https://lore.kernel.org/all/20250625183758.444626478@linutronix.de
Update the auxiliary timekeepers periodically. For now this is tied to the system
timekeeper update from the tick. This might be revisited and moved out of the tick.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: John Stultz <jstultz@google.com>
Link: https://lore.kernel.org/all/20250625183758.382451331@linutronix.de
The behaviour is close to clock_adtime(CLOCK_REALTIME) with the
following differences:
1) ADJ_SETOFFSET adjusts the auxiliary clock offset
2) ADJ_TAI is not supported
3) Leap seconds are not supported
4) PPS is not supported
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: John Stultz <jstultz@google.com>
Link: https://lore.kernel.org/all/20250625183758.317946543@linutronix.de
Exclude ADJ_TAI, leap seconds and PPS functionality as they make no sense
in the context of auxiliary clocks and provide a time stamp based on the
actual clock.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: John Stultz <jstultz@google.com>
Link: https://lore.kernel.org/all/20250625183758.253203783@linutronix.de
Split out the actual functionality of adjtimex() and make do_adjtimex() a
wrapper which feeds the core timekeeper into it and handles the result
including audit at the call site.
This allows to reuse the actual functionality for auxiliary clocks.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: John Stultz <jstultz@google.com>
Link: https://lore.kernel.org/all/20250625183758.187322876@linutronix.de
Redirect the relative offset adjustment to the auxiliary clock offset
instead of modifying CLOCK_REALTIME, which has no meaning in context of
these clocks.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: John Stultz <jstultz@google.com>
Link: https://lore.kernel.org/all/20250625183758.124057787@linutronix.de
Add clock_settime(2) support for auxiliary clocks. The function affects the
AUX offset which is added to the "monotonic" clock readout of these clocks.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: John Stultz <jstultz@google.com>
Link: https://lore.kernel.org/all/20250625183757.995688714@linutronix.de
Provide interfaces similar to the ktime_get*() family which provide access
to the auxiliary clocks.
These interfaces have a boolean return value, which indicates whether the
accessed clock is valid or not.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: John Stultz <jstultz@google.com>
Link: https://lore.kernel.org/all/20250625183757.868342628@linutronix.de
Propagate a system clocksource change to the auxiliary timekeepers so that
they can pick up the new clocksource.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: John Stultz <jstultz@google.com>
Link: https://lore.kernel.org/all/20250625183757.803890875@linutronix.de
Provide timekeepers for auxiliary clocks and initialize them during
boot.
Signed-off-by: Anna-Maria Behnsen <anna-maria@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: John Stultz <jstultz@google.com>
Link: https://lore.kernel.org/all/20250519083026.350061049@linutronix.de
In preparation for supporting independent auxiliary timekeepers, add a
clock valid field and set it to true for the system timekeeper.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: John Stultz <jstultz@google.com>
Link: https://lore.kernel.org/all/20250519083026.287145536@linutronix.de
Don't invoke the VDSO and paravirt updates when utilized for auxiliary
clocks. This is a temporary workaround until the VDSO and paravirt
interfaces have been worked out.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/20250519083026.223876435@linutronix.de
In __timekeeping_advance() the pointer to struct tk_data is hardcoded by the
use of &tk_core. As long as there is only a single timekeeper (tk_core),
this is not a problem. But when __timekeeping_advance() will be reused for
per auxiliary timekeepers, __timekeeping_advance() needs to be generalized.
Add a pointer to struct tk_data as function argument of
__timekeeping_advance() and adapt all call sites.
Signed-off-by: Anna-Maria Behnsen <anna-maria@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: John Stultz <jstultz@google.com>
Link: https://lore.kernel.org/all/20250519083026.160967312@linutronix.de
In preparation for supporting auxiliary POSIX clocks, add a timekeeper ID
to the relevant functions.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: John Stultz <jstultz@google.com>
Link: https://lore.kernel.org/all/20250519083026.032425931@linutronix.de
If auxiliary clocks are enabled, provide an array of NTP data so that the
auxiliary timekeepers can be steered independently of the core timekeeper.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: John Stultz <jstultz@google.com>
Link: https://lore.kernel.org/all/20250519083025.969000914@linutronix.de
To support auxiliary timekeeping and the related user space interfaces,
it's required to define a clock ID range for them.
Reserve 8 auxiliary clock IDs after the regular timekeeping clock ID space.
This is the maximum number of auxiliary clocks the kernel can support. The actual
number of supported clocks depends obviously on the presence of related devices
and might be constraint by the available VDSO space.
Add the corresponding timekeeper IDs as well.
Signed-off-by: Anna-Maria Behnsen <anna-maria@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: John Stultz <jstultz@google.com>
Link: https://lore.kernel.org/all/20250519083025.905800695@linutronix.de
As long as there is only a single timekeeper, there is no need to clarify
which timekeeper is used. But with the upcoming reusage of the timekeeper
infrastructure for auxiliary clock timekeepers, an ID is required to
differentiate.
Introduce an enum for timekeeper IDs, introduce a field in struct tk_data
to store this timekeeper id and add also initialization. The id struct
field is added at the end of the second cachline, as there is a 4 byte hole
anyway.
Signed-off-by: Anna-Maria Behnsen <anna-maria@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: John Stultz <jstultz@google.com>
Link: https://lore.kernel.org/all/20250519083025.842476378@linutronix.de
This was overlooked in the initial conversion. Use the provided pointer to
access the shadow timekeeper.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: John Stultz <jstultz@google.com>
Link: https://lore.kernel.org/all/20250519083025.652611452@linutronix.de
cpumask_next_wrap() is more verbose and efficient comparing to
cpumask_next() followed by cpumask_first().
Signed-off-by: Yury Norov [NVIDIA] <yury.norov@gmail.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: John Stultz <jstultz@google.com>
Link: https://lore.kernel.org/all/20250614155031.340988-3-yury.norov@gmail.com
cpumask_any_but() is more verbose than cpumask_first() followed by
cpumask_next(). Use it in clocksource_verify_choose_cpus().
Signed-off-by: Yury Norov [NVIDIA] <yury.norov@gmail.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: John Stultz <jstultz@google.com>
Link: https://lore.kernel.org/all/20250614155031.340988-2-yury.norov@gmail.com
If an exiting non-autoreaping task has already passed exit_notify() and
calls handle_posix_cpu_timers() from IRQ, it can be reaped by its parent
or debugger right after unlock_task_sighand().
If a concurrent posix_cpu_timer_del() runs at that moment, it won't be
able to detect timer->it.cpu.firing != 0: cpu_timer_task_rcu() and/or
lock_task_sighand() will fail.
Add the tsk->exit_state check into run_posix_cpu_timers() to fix this.
This fix is not needed if CONFIG_POSIX_CPU_TIMERS_TASK_WORK=y, because
exit_task_work() is called before exit_notify(). But the check still
makes sense, task_work_add(&tsk->posix_cputimers_work.work) will fail
anyway in this case.
Cc: stable@vger.kernel.org
Reported-by: Benoît Sevens <bsevens@google.com>
Fixes: 0bdd2ed413 ("sched: run_posix_cpu_timers: Don't check ->exit_state, use lock_task_sighand()")
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Make the logic easier to follow:
- Remove the final return statement, which is never reached, and move the
actual walk-terminating return statement out of the do-while loop.
- Remove the else-clause to reduce indentation. If a non-lonely group is
encountered during the walk, the loop is immediately terminated with a
return statement anyway; no need for an else.
Signed-off-by: Petr Tesarik <ptesarik@suse.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Link: https://lore.kernel.org/all/20250606124818.455560-1-ptesarik@suse.com
Move this API to the canonical timer_*() namespace.
[ tglx: Redone against pre rc1 ]
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/aB2X0jCKQO56WdMt@gmail.com
- Rework the initialization of the posix-timer kmem_cache and move the
cache pointer into the timer_data structure to prevent false sharing.
- Switch the alarmtimer code to lock guards.
- Improve the CPU selection criteria in the per CPU validation of the
clocksource watchdog to avoid arbitrary selections (or omissions) on
systems with a small number of CPUs.
- The usual cleanups and improvements
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Merge tag 'timers-core-2025-05-25' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull timer core updates from Thomas Gleixner:
"Updates for the time/timer core code:
- Rework the initialization of the posix-timer kmem_cache and move
the cache pointer into the timer_data structure to prevent false
sharing
- Switch the alarmtimer code to lock guards
- Improve the CPU selection criteria in the per CPU validation of the
clocksource watchdog to avoid arbitrary selections (or omissions)
on systems with a small number of CPUs
- The usual cleanups and improvements"
* tag 'timers-core-2025-05-25' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
tick/nohz: Remove unused tick_nohz_full_add_cpus_to()
clocksource: Fix the CPUs' choice in the watchdog per CPU verification
alarmtimer: Switch spin_{lock,unlock}_irqsave() to guards
alarmtimer: Remove dead return value in clock2alarm()
time/jiffies: Change register_refined_jiffies() to void __init
timers: Remove unused __round_jiffies(_up)
posix-timers: Initialize cache early and move pointer into __timer_data
- Convert init_timer*(), try_to_del_timer_sync() and
destroy_timer_on_stack() over to the canonical timer_*() namespace
convention.
There are is another large converstion pending, which has not been included
because it would have caused a gazillion of merge conflicts in next. The
conversion scripts will be run towards the end of the merge window and a
pull request sent once all conflict dependencies have been merged.
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Merge tag 'timers-cleanups-2025-05-25' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull timer cleanups from Thomas Gleixner:
"Another set of timer API cleanups:
- Convert init_timer*(), try_to_del_timer_sync() and
destroy_timer_on_stack() over to the canonical timer_*()
namespace convention.
There is another large conversion pending, which has not been included
because it would have caused a gazillion of merge conflicts in next.
The conversion scripts will be run towards the end of the merge window
and a pull request sent once all conflict dependencies have been
merged"
* tag 'timers-cleanups-2025-05-25' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
treewide, timers: Rename destroy_timer_on_stack() as timer_destroy_on_stack()
treewide, timers: Rename try_to_del_timer_sync() as timer_delete_sync_try()
timers: Rename init_timers() as timers_init()
timers: Rename NEXT_TIMER_MAX_DELTA as TIMER_NEXT_MAX_DELTA
timers: Rename __init_timer_on_stack() as __timer_init_on_stack()
timers: Rename __init_timer() as __timer_init()
timers: Rename init_timer_on_stack_key() as timer_init_key_on_stack()
timers: Rename init_timer_key() as timer_init_key()
Right now, if the clocksource watchdog detects a clocksource skew, it might
perform a per CPU check, for example in the TSC case on x86. In other
words: supposing TSC is detected as unstable by the clocksource watchdog
running at CPU1, as part of marking TSC unstable the kernel will also run a
check of TSC readings on some CPUs to be sure it is synced between them
all.
But that check happens only on some CPUs, not all of them; this choice is
based on the parameter "verify_n_cpus" and in some random cpumask
calculation. So, the watchdog runs such per CPU checks on up to
"verify_n_cpus" random CPUs among all online CPUs, with the risk of
repeating CPUs (that aren't double checked) in the cpumask random
calculation.
But if "verify_n_cpus" > num_online_cpus(), it should skip the random
calculation and just go ahead and check the clocksource sync between
all online CPUs, without the risk of skipping some CPUs due to
duplicity in the random cpumask calculation.
Tests in a 4 CPU laptop with TSC skew detected led to some cases of the per
CPU verification skipping some CPU even with verify_n_cpus=8, due to the
duplicity on random cpumask generation. Skipping the randomization when the
number of online CPUs is smaller than verify_n_cpus, solves that.
Suggested-by: Thadeu Lima de Souza Cascardo <cascardo@igalia.com>
Signed-off-by: Guilherme G. Piccoli <gpiccoli@igalia.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Paul E. McKenney <paulmck@kernel.org>
Link: https://lore.kernel.org/all/20250323173857.372390-1-gpiccoli@igalia.com
Using guard/scoped_guard() to simplify code. Using guard() to remove
'goto unlock' label is neater especially.
[ tglx: Brought back the scoped_guard()'s which were dropped in v2 and
simplified alarmtimer_rtc_add_device() ]
Signed-off-by: Su Hui <suhui@nfschina.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: John Stultz <jstultz@google.com>
Link: https://lore.kernel.org/all/20250430032734.2079290-4-suhui@nfschina.com
'clockid' can only be ALARM_REALTIME and ALARM_BOOTTIME. It's impossible to
return -1 and callers never check the return value.
Only alarm_clock_get_timespec(), alarm_clock_get_ktime(),
alarm_timer_create() and alarm_timer_nsleep() call clock2alarm(). These
callers use clockid_to_kclock() to get 'struct k_clock', which ensures
that clock2alarm() never returns -1.
Remove the impossible -1 return value, and add a warning to notify about any
future misuse of this function.
Signed-off-by: Su Hui <suhui@nfschina.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/20250430032734.2079290-3-suhui@nfschina.com
register_refined_jiffies() is only used in setup code and always returns 0.
Mark it as __init to save some bytes and change it to void.
Signed-off-by: Su Hui <suhui@nfschina.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/20250430032734.2079290-2-suhui@nfschina.com
Lei Chen raised an issue with CLOCK_MONOTONIC_COARSE seeing time
inconsistencies. Lei tracked down that this was being caused by the
adjustment:
tk->tkr_mono.xtime_nsec -= offset;
which is made to compensate for the unaccumulated cycles in offset when the
multiplicator is adjusted forward, so that the non-_COARSE clockids don't
see inconsistencies.
However, the _COARSE clockid getter functions use the adjusted xtime_nsec
value directly and do not compensate the negative offset via the
clocksource delta multiplied with the new multiplicator. In that case the
caller can observe time going backwards in consecutive calls.
By design, this negative adjustment should be fine, because the logic run
from timekeeping_adjust() is done after it accumulated approximately
multiplicator * interval_cycles
into xtime_nsec. The accumulated value is always larger then the
mult_adj * offset
value, which is subtracted from xtime_nsec. Both operations are done
together under the tk_core.lock, so the net change to xtime_nsec is always
always be positive.
However, do_adjtimex() calls into timekeeping_advance() as well, to
apply the NTP frequency adjustment immediately. In this case,
timekeeping_advance() does not return early when the offset is smaller
then interval_cycles. In that case there is no time accumulated into
xtime_nsec. But the subsequent call into timekeeping_adjust(), which
modifies the multiplicator, subtracts from xtime_nsec to correct for the
new multiplicator.
Here because there was no accumulation, xtime_nsec becomes smaller than
before, which opens a window up to the next accumulation, where the
_COARSE clockid getters, which don't compensate for the offset, can
observe the inconsistency.
This has been tried to be fixed by forwarding the timekeeper in the case
that adjtimex() adjusts the multiplier, which resets the offset to zero:
757b000f7b ("timekeeping: Fix possible inconsistencies in _COARSE clockids")
That works correctly, but unfortunately causes a regression on the
adjtimex() side. There are two issues:
1) The forwarding of the base time moves the update out of the original
period and establishes a new one.
2) The clearing of the accumulated NTP error is changing the behaviour as
well.
User-space expects that multiplier/frequency updates are in effect, when the
syscall returns, so delaying the update to the next tick is not solving the
problem either.
Commit 757b000f7b was reverted so that the established expectations of
user space implementations (ntpd, chronyd) are restored, but that obviously
brought the inconsistencies back.
One of the initial approaches to fix this was to establish a separate
storage for the coarse time getter nanoseconds part by calculating it from
the offset. That was dropped on the floor because not having yet another
state to maintain was simpler. But given the result of the above exercise,
this solution turns out to be the right one. Bring it back in a slightly
modified form.
Thus introduce timekeeper::coarse_nsec and store that nanoseconds part in
it, switch the time getter functions and the VDSO update to use that value.
coarse_nsec is set on operations which forward or initialize the timekeeper
and after time was accumulated during a tick. If there is no accumulation
the timestamp is unchanged.
This leaves the adjtimex() behaviour unmodified and prevents coarse time
from going backwards.
[ jstultz: Simplified the coarse_nsec calculation and kept behavior so
coarse clockids aren't adjusted on each inter-tick adjtimex
call, slightly reworked the comments and commit message ]
Fixes: da15cfdae0 ("time: Introduce CLOCK_REALTIME_COARSE")
Reported-by: Lei Chen <lei.chen@smartx.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: John Stultz <jstultz@google.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/all/20250419054706.2319105-1-jstultz@google.com
Closes: https://lore.kernel.org/lkml/20250310030004.3705801-1-lei.chen@smartx.com/
Remove two trivial but long unused functions.
__round_jiffies() has been unused since 2008's
commit 9c133c469d ("Add round_jiffies_up and related routines")
__round_jiffies_up() has been unused since 2019's
commit 7ae3f6e130 ("powerpc/watchdog: Use hrtimers for per-CPU
heartbeat")
Remove them.
Signed-off-by: Dr. David Alan Gilbert <linux@treblig.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/20250418200803.427911-1-linux@treblig.org
Move posix_timers_cache initialization to posixtimer_init(). At that point
the memory subsystem is already up and running.
Also move the cache pointer to the __timer_data variable to avoid
potential false sharing, since it never was marked as __ro_after_init.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/20250402133114.253901-1-edumazet@google.com
1) Convert all del_timer[_sync]() instances over to the new
timer_delete[_sync]() API and remove the legacy wrappers.
Conversion was done with coccinelle plus some manual fixups as
coccinelle chokes on scoped_guard().
2) The final cleanup of the hrtimer_init() to hrtimer_setup() conversion.
This has been delayed to the end of the merge window, so that all
patches which have been merged through other trees are in mainline and
all new users are catched.
Doing this right before rc1 ensures that new code which is merged post rc1
is not introducing new instances of the original functionality.
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Merge tag 'timers-cleanups-2025-04-06' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull timer cleanups from Thomas Gleixner:
"A set of final cleanups for the timer subsystem:
- Convert all del_timer[_sync]() instances over to the new
timer_delete[_sync]() API and remove the legacy wrappers.
Conversion was done with coccinelle plus some manual fixups as
coccinelle chokes on scoped_guard().
- The final cleanup of the hrtimer_init() to hrtimer_setup()
conversion.
This has been delayed to the end of the merge window, so that all
patches which have been merged through other trees are in mainline
and all new users are catched.
Doing this right before rc1 ensures that new code which is merged post
rc1 is not introducing new instances of the original functionality"
* tag 'timers-cleanups-2025-04-06' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
tracing/timers: Rename the hrtimer_init event to hrtimer_setup
hrtimers: Rename debug_init_on_stack() to debug_setup_on_stack()
hrtimers: Rename debug_init() to debug_setup()
hrtimers: Rename __hrtimer_init_sleeper() to __hrtimer_setup_sleeper()
hrtimers: Remove unnecessary NULL check in hrtimer_start_range_ns()
hrtimers: Make callback function pointer private
hrtimers: Merge __hrtimer_init() into __hrtimer_setup()
hrtimers: Switch to use __htimer_setup()
hrtimers: Delete hrtimer_init()
treewide: Convert new and leftover hrtimer_init() users
treewide: Switch/rename to timer_delete[_sync]()
The function hrtimer_init() doesn't exist anymore. It was replaced by
hrtimer_setup().
Thus, rename the hrtimer_init trace event to hrtimer_setup to keep it
consistent.
Signed-off-by: Nam Cao <namcao@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/all/cba84c3d853c5258aa3a262363a6eac08e2c7afc.1738746927.git.namcao@linutronix.de
All the hrtimer_init*() functions have been renamed to hrtimer_setup*().
Rename debug_init_on_stack() to debug_setup_on_stack() as well, to keep the
names consistent.
Signed-off-by: Nam Cao <namcao@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/all/073cf6162779a2f5b12624677d4c49ee7eccc1ed.1738746927.git.namcao@linutronix.de
All the hrtimer_init*() functions have been renamed to hrtimer_setup*().
Rename __hrtimer_init_sleeper() to __hrtimer_setup_sleeper() as well, to
keep the names consistent.
Signed-off-by: Nam Cao <namcao@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/all/807694aedad9353421c4a7347629a30c5c31026f.1738746927.git.namcao@linutronix.de
The struct hrtimer::function field can only be changed using
hrtimer_setup*() or hrtimer_update_function(), and both already null-check
'function'. Therefore, null-checking 'function' in hrtimer_start_range_ns()
is not necessary.
Signed-off-by: Nam Cao <namcao@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/all/4661c571ee87980c340ccc318fc1a473c0c8f6bc.1738746927.git.namcao@linutronix.de
Make the struct hrtimer::function field private, to prevent users from
changing this field in an unsafe way. hrtimer_update_function() should be
used if the callback function needs to be changed.
Signed-off-by: Nam Cao <namcao@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/all/7d0e6e0c5c59a64a9bea940051aac05d750bc0c2.1738746927.git.namcao@linutronix.de
__hrtimer_init_sleeper() calls __hrtimer_init() and also sets up the
callback function. But there is already __hrtimer_setup() which does both
actions.
Switch to use __hrtimer_setup() to simplify the code.
Signed-off-by: Nam Cao <namcao@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/all/d9a45a51b6a8aa0045310d63f73753bf6b33f385.1738746927.git.namcao@linutronix.de
timer_delete[_sync]() replaces del_timer[_sync](). Convert the whole tree
over and remove the historical wrapper inlines.
Conversion was done with coccinelle plus manual fixups where necessary.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This reverts commit 757b000f7b.
Miroslav reported that the changes for handling the inconsistencies in the
coarse time getters result in a regression on the adjtimex() side.
There are two issues:
1) The forwarding of the base time moves the update out of the original
period and establishes a new one.
2) The clearing of the accumulated NTP error is changing the behaviour as
well.
Userspace expects that multiplier/frequency updates are in effect, when the
syscall returns, so delaying the update to the next tick is not solving the
problem either.
Revert the change, so that the established expectations of user space
implementations (ntpd, chronyd) are restored. The re-introduced
inconsistency of the coarse time getters will be addressed in a subsequent
fix.
Fixes: 757b000f7b ("timekeeping: Fix possible inconsistencies in _COARSE clockids")
Reported-by: Miroslav Lichvar <mlichvar@redhat.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/Z-qsg6iDGlcIJulJ@localhost
Core & protocols
----------------
- Continue Netlink conversions to per-namespace RTNL lock
(IPv4 routing, routing rules, routing next hops, ARP ioctls).
- Continue extending the use of netdev instance locks. As a driver
opt-in protect queue operations and (in due course) ethtool
operations with the instance lock and not RTNL lock.
- Support collecting TCP timestamps (data submitted, sent, acked)
in BPF, allowing for transparent (to the application) and lower
overhead tracking of TCP RPC performance.
- Tweak existing networking Rx zero-copy infra to support zero-copy
Rx via io_uring.
- Optimize MPTCP performance in single subflow mode by 29%.
- Enable GRO on packets which went thru XDP CPU redirect (were queued
for processing on a different CPU). Improving TCP stream performance
up to 2x.
- Improve performance of contended connect() by 200% by searching
for an available 4-tuple under RCU rather than a spin lock.
Bring an additional 229% improvement by tweaking hash distribution.
- Avoid unconditionally touching sk_tsflags on RX, improving
performance under UDP flood by as much as 10%.
- Avoid skb_clone() dance in ping_rcv() to improve performance under
ping flood.
- Avoid FIB lookup in netfilter if socket is available, 20% perf win.
- Rework network device creation (in-kernel) API to more clearly
identify network namespaces and their roles.
There are up to 4 namespace roles but we used to have just 2 netns
pointer arguments, interpreted differently based on context.
- Use sysfs_break_active_protection() instead of trylock to avoid
deadlocks between unregistering objects and sysfs access.
- Add a new sysctl and sockopt for capping max retransmit timeout
in TCP.
- Support masking port and DSCP in routing rule matches.
- Support dumping IPv4 multicast addresses with RTM_GETMULTICAST.
- Support specifying at what time packet should be sent on AF_XDP
sockets.
- Expose TCP ULP diagnostic info (for TLS and MPTCP) to non-admin users.
- Add Netlink YAML spec for WiFi (nl80211) and conntrack.
- Introduce EXPORT_IPV6_MOD() and EXPORT_IPV6_MOD_GPL() for symbols
which only need to be exported when IPv6 support is built as a module.
- Age FDB entries based on Rx not Tx traffic in VxLAN, similar
to normal bridging.
- Allow users to specify source port range for GENEVE tunnels.
- netconsole: allow attaching kernel release, CPU ID and task name
to messages as metadata
Driver API
----------
- Continue rework / fixing of Energy Efficient Ethernet (EEE) across
the SW layers. Delegate the responsibilities to phylink where possible.
Improve its handling in phylib.
- Support symmetric OR-XOR RSS hashing algorithm.
- Support tracking and preserving IRQ affinity by NAPI itself.
- Support loopback mode speed selection for interface selftests.
Device drivers
--------------
- Remove the IBM LCS driver for s390.
- Remove the sb1000 cable modem driver.
- Add support for SFP module access over SMBus.
- Add MCTP transport driver for MCTP-over-USB.
- Enable XDP metadata support in multiple drivers.
- Ethernet high-speed NICs:
- Broadcom (bnxt):
- add PCIe TLP Processing Hints (TPH) support for new AMD platforms
- support dumping RoCE queue state for debug
- opt into instance locking
- Intel (100G, ice, idpf):
- ice: rework MSI-X IRQ management and distribution
- ice: support for E830 devices
- iavf: add support for Rx timestamping
- iavf: opt into instance locking
- nVidia/Mellanox:
- mlx4: use page pool memory allocator for Rx
- mlx5: support for one PTP device per hardware clock
- mlx5: support for 200Gbps per-lane link modes
- mlx5: move IPSec policy check after decryption
- AMD/Solarflare:
- support FW flashing via devlink
- Cisco (enic):
- use page pool memory allocator for Rx
- enable 32, 64 byte CQEs
- get max rx/tx ring size from the device
- Meta (fbnic):
- support flow steering and RSS configuration
- report queue stats
- support TCP segmentation
- support IRQ coalescing
- support ring size configuration
- Marvell/Cavium:
- support AF_XDP
- Wangxun:
- support for PTP clock and timestamping
- Huawei (hibmcge):
- checksum offload
- add more statistics
- Ethernet virtual:
- VirtIO net:
- aggressively suppress Tx completions, improve perf by 96% with
1 CPU and 55% with 2 CPUs
- expose NAPI to IRQ mapping and persist NAPI settings
- Google (gve):
- support XDP in DQO RDA Queue Format
- opt into instance locking
- Microsoft vNIC:
- support BIG TCP
- Ethernet NICs consumer, and embedded:
- Synopsys (stmmac):
- cleanup Tx and Tx clock setting and other link-focused cleanups
- enable SGMII and 2500BASEX mode switching for Intel platforms
- support Sophgo SG2044
- Broadcom switches (b53):
- support for BCM53101
- TI:
- iep: add perout configuration support
- icssg: support XDP
- Cadence (macb):
- implement BQL
- Xilinx (axinet):
- support dynamic IRQ moderation and changing coalescing at runtime
- implement BQL
- report standard stats
- MediaTek:
- support phylink managed EEE
- Intel:
- igc: don't restart the interface on every XDP program change
- RealTek (r8169):
- support reading registers of internal PHYs directly
- increase max jumbo packet size on RTL8125/RTL8126
- Airoha:
- support for RISC-V NPU packet processing unit
- enable scatter-gather and support MTU up to 9kB
- Tehuti (tn40xx):
- support cards with TN4010 MAC and an Aquantia AQR105 PHY
- Ethernet PHYs:
- support for TJA1102S, TJA1121
- dp83tg720: add randomized polling intervals for link detection
- dp83822: support changing the transmit amplitude voltage
- support for LEDs on 88q2xxx
- CAN:
- canxl: support Remote Request Substitution bit access
- flexcan: add S32G2/S32G3 SoC
- WiFi:
- remove cooked monitor support
- strict mode for better AP testing
- basic EPCS support
- OMI RX bandwidth reduction support
- batman-adv: add support for jumbo frames
- WiFi drivers:
- RealTek (rtw88):
- support RTL8814AE and RTL8814AU
- RealTek (rtw89):
- switch using wiphy_lock and wiphy_work
- add BB context to manipulate two PHY as preparation of MLO
- improve BT-coexistence mechanism to play A2DP smoothly
- Intel (iwlwifi):
- add new iwlmld sub-driver for latest HW/FW combinations
- MediaTek (mt76):
- preparation for mt7996 Multi-Link Operation (MLO) support
- Qualcomm/Atheros (ath12k):
- continued work on MLO
- Silabs (wfx):
- Wake-on-WLAN support
- Bluetooth:
- add support for skb TX SND/COMPLETION timestamping
- hci_core: enable buffer flow control for SCO/eSCO
- coredump: log devcd dumps into the monitor
- Bluetooth drivers:
- intel: add support to configure TX power
- nxp: handle bootloader error during cmd5 and cmd7
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
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Merge tag 'net-next-6.15' of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next
Pull networking updates from Jakub Kicinski:
"Core & protocols:
- Continue Netlink conversions to per-namespace RTNL lock
(IPv4 routing, routing rules, routing next hops, ARP ioctls)
- Continue extending the use of netdev instance locks. As a driver
opt-in protect queue operations and (in due course) ethtool
operations with the instance lock and not RTNL lock.
- Support collecting TCP timestamps (data submitted, sent, acked) in
BPF, allowing for transparent (to the application) and lower
overhead tracking of TCP RPC performance.
- Tweak existing networking Rx zero-copy infra to support zero-copy
Rx via io_uring.
- Optimize MPTCP performance in single subflow mode by 29%.
- Enable GRO on packets which went thru XDP CPU redirect (were queued
for processing on a different CPU). Improving TCP stream
performance up to 2x.
- Improve performance of contended connect() by 200% by searching for
an available 4-tuple under RCU rather than a spin lock. Bring an
additional 229% improvement by tweaking hash distribution.
- Avoid unconditionally touching sk_tsflags on RX, improving
performance under UDP flood by as much as 10%.
- Avoid skb_clone() dance in ping_rcv() to improve performance under
ping flood.
- Avoid FIB lookup in netfilter if socket is available, 20% perf win.
- Rework network device creation (in-kernel) API to more clearly
identify network namespaces and their roles. There are up to 4
namespace roles but we used to have just 2 netns pointer arguments,
interpreted differently based on context.
- Use sysfs_break_active_protection() instead of trylock to avoid
deadlocks between unregistering objects and sysfs access.
- Add a new sysctl and sockopt for capping max retransmit timeout in
TCP.
- Support masking port and DSCP in routing rule matches.
- Support dumping IPv4 multicast addresses with RTM_GETMULTICAST.
- Support specifying at what time packet should be sent on AF_XDP
sockets.
- Expose TCP ULP diagnostic info (for TLS and MPTCP) to non-admin
users.
- Add Netlink YAML spec for WiFi (nl80211) and conntrack.
- Introduce EXPORT_IPV6_MOD() and EXPORT_IPV6_MOD_GPL() for symbols
which only need to be exported when IPv6 support is built as a
module.
- Age FDB entries based on Rx not Tx traffic in VxLAN, similar to
normal bridging.
- Allow users to specify source port range for GENEVE tunnels.
- netconsole: allow attaching kernel release, CPU ID and task name to
messages as metadata
Driver API:
- Continue rework / fixing of Energy Efficient Ethernet (EEE) across
the SW layers. Delegate the responsibilities to phylink where
possible. Improve its handling in phylib.
- Support symmetric OR-XOR RSS hashing algorithm.
- Support tracking and preserving IRQ affinity by NAPI itself.
- Support loopback mode speed selection for interface selftests.
Device drivers:
- Remove the IBM LCS driver for s390
- Remove the sb1000 cable modem driver
- Add support for SFP module access over SMBus
- Add MCTP transport driver for MCTP-over-USB
- Enable XDP metadata support in multiple drivers
- Ethernet high-speed NICs:
- Broadcom (bnxt):
- add PCIe TLP Processing Hints (TPH) support for new AMD
platforms
- support dumping RoCE queue state for debug
- opt into instance locking
- Intel (100G, ice, idpf):
- ice: rework MSI-X IRQ management and distribution
- ice: support for E830 devices
- iavf: add support for Rx timestamping
- iavf: opt into instance locking
- nVidia/Mellanox:
- mlx4: use page pool memory allocator for Rx
- mlx5: support for one PTP device per hardware clock
- mlx5: support for 200Gbps per-lane link modes
- mlx5: move IPSec policy check after decryption
- AMD/Solarflare:
- support FW flashing via devlink
- Cisco (enic):
- use page pool memory allocator for Rx
- enable 32, 64 byte CQEs
- get max rx/tx ring size from the device
- Meta (fbnic):
- support flow steering and RSS configuration
- report queue stats
- support TCP segmentation
- support IRQ coalescing
- support ring size configuration
- Marvell/Cavium:
- support AF_XDP
- Wangxun:
- support for PTP clock and timestamping
- Huawei (hibmcge):
- checksum offload
- add more statistics
- Ethernet virtual:
- VirtIO net:
- aggressively suppress Tx completions, improve perf by 96%
with 1 CPU and 55% with 2 CPUs
- expose NAPI to IRQ mapping and persist NAPI settings
- Google (gve):
- support XDP in DQO RDA Queue Format
- opt into instance locking
- Microsoft vNIC:
- support BIG TCP
- Ethernet NICs consumer, and embedded:
- Synopsys (stmmac):
- cleanup Tx and Tx clock setting and other link-focused
cleanups
- enable SGMII and 2500BASEX mode switching for Intel platforms
- support Sophgo SG2044
- Broadcom switches (b53):
- support for BCM53101
- TI:
- iep: add perout configuration support
- icssg: support XDP
- Cadence (macb):
- implement BQL
- Xilinx (axinet):
- support dynamic IRQ moderation and changing coalescing at
runtime
- implement BQL
- report standard stats
- MediaTek:
- support phylink managed EEE
- Intel:
- igc: don't restart the interface on every XDP program change
- RealTek (r8169):
- support reading registers of internal PHYs directly
- increase max jumbo packet size on RTL8125/RTL8126
- Airoha:
- support for RISC-V NPU packet processing unit
- enable scatter-gather and support MTU up to 9kB
- Tehuti (tn40xx):
- support cards with TN4010 MAC and an Aquantia AQR105 PHY
- Ethernet PHYs:
- support for TJA1102S, TJA1121
- dp83tg720: add randomized polling intervals for link detection
- dp83822: support changing the transmit amplitude voltage
- support for LEDs on 88q2xxx
- CAN:
- canxl: support Remote Request Substitution bit access
- flexcan: add S32G2/S32G3 SoC
- WiFi:
- remove cooked monitor support
- strict mode for better AP testing
- basic EPCS support
- OMI RX bandwidth reduction support
- batman-adv: add support for jumbo frames
- WiFi drivers:
- RealTek (rtw88):
- support RTL8814AE and RTL8814AU
- RealTek (rtw89):
- switch using wiphy_lock and wiphy_work
- add BB context to manipulate two PHY as preparation of MLO
- improve BT-coexistence mechanism to play A2DP smoothly
- Intel (iwlwifi):
- add new iwlmld sub-driver for latest HW/FW combinations
- MediaTek (mt76):
- preparation for mt7996 Multi-Link Operation (MLO) support
- Qualcomm/Atheros (ath12k):
- continued work on MLO
- Silabs (wfx):
- Wake-on-WLAN support
- Bluetooth:
- add support for skb TX SND/COMPLETION timestamping
- hci_core: enable buffer flow control for SCO/eSCO
- coredump: log devcd dumps into the monitor
- Bluetooth drivers:
- intel: add support to configure TX power
- nxp: handle bootloader error during cmd5 and cmd7"
* tag 'net-next-6.15' of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next: (1681 commits)
unix: fix up for "apparmor: add fine grained af_unix mediation"
mctp: Fix incorrect tx flow invalidation condition in mctp-i2c
net: usb: asix: ax88772: Increase phy_name size
net: phy: Introduce PHY_ID_SIZE — minimum size for PHY ID string
net: libwx: fix Tx L4 checksum
net: libwx: fix Tx descriptor content for some tunnel packets
atm: Fix NULL pointer dereference
net: tn40xx: add pci-id of the aqr105-based Tehuti TN4010 cards
net: tn40xx: prepare tn40xx driver to find phy of the TN9510 card
net: tn40xx: create swnode for mdio and aqr105 phy and add to mdiobus
net: phy: aquantia: add essential functions to aqr105 driver
net: phy: aquantia: search for firmware-name in fwnode
net: phy: aquantia: add probe function to aqr105 for firmware loading
net: phy: Add swnode support to mdiobus_scan
gve: add XDP DROP and PASS support for DQ
gve: update XDP allocation path support RX buffer posting
gve: merge packet buffer size fields
gve: update GQ RX to use buf_size
gve: introduce config-based allocation for XDP
gve: remove xdp_xsk_done and xdp_xsk_wakeup statistics
...
- Consolidate the VDSO storage
The VDSO data storage and data layout has been largely architecture
specific for historical reasons. That increases the maintenance effort
and causes inconsistencies over and over.
There is no real technical reason for architecture specific layouts and
implementations. The architecture specific details can easily be
integrated into a generic layout, which also reduces the amount of
duplicated code for managing the mappings.
Convert all architectures over to a unified layout and common mapping
infrastructure. This splits the VDSO data layout into subsystem
specific blocks, timekeeping, random and architecture parts, which
provides a better structure and allows to improve and update the
functionalities without conflict and interaction.
- Rework the timekeeping data storage
The current implementation is designed for exposing system timekeeping
accessors, which was good enough at the time when it was designed.
PTP and Time Sensitive Networking (TSN) change that as there are
requirements to expose independent PTP clocks, which are not related to
system timekeeping.
Replace the monolithic data storage by a structured layout, which
allows to add support for independent PTP clocks on top while reusing
both the data structures and the time accessor implementations.
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Merge tag 'timers-vdso-2025-03-23' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull VDSO infrastructure updates from Thomas Gleixner:
- Consolidate the VDSO storage
The VDSO data storage and data layout has been largely architecture
specific for historical reasons. That increases the maintenance
effort and causes inconsistencies over and over.
There is no real technical reason for architecture specific layouts
and implementations. The architecture specific details can easily be
integrated into a generic layout, which also reduces the amount of
duplicated code for managing the mappings.
Convert all architectures over to a unified layout and common mapping
infrastructure. This splits the VDSO data layout into subsystem
specific blocks, timekeeping, random and architecture parts, which
provides a better structure and allows to improve and update the
functionalities without conflict and interaction.
- Rework the timekeeping data storage
The current implementation is designed for exposing system
timekeeping accessors, which was good enough at the time when it was
designed.
PTP and Time Sensitive Networking (TSN) change that as there are
requirements to expose independent PTP clocks, which are not related
to system timekeeping.
Replace the monolithic data storage by a structured layout, which
allows to add support for independent PTP clocks on top while reusing
both the data structures and the time accessor implementations.
* tag 'timers-vdso-2025-03-23' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (55 commits)
sparc/vdso: Always reject undefined references during linking
x86/vdso: Always reject undefined references during linking
vdso: Rework struct vdso_time_data and introduce struct vdso_clock
vdso: Move architecture related data before basetime data
powerpc/vdso: Prepare introduction of struct vdso_clock
arm64/vdso: Prepare introduction of struct vdso_clock
x86/vdso: Prepare introduction of struct vdso_clock
time/namespace: Prepare introduction of struct vdso_clock
vdso/namespace: Rename timens_setup_vdso_data() to reflect new vdso_clock struct
vdso/vsyscall: Prepare introduction of struct vdso_clock
vdso/gettimeofday: Prepare helper functions for introduction of struct vdso_clock
vdso/gettimeofday: Prepare do_coarse_timens() for introduction of struct vdso_clock
vdso/gettimeofday: Prepare do_coarse() for introduction of struct vdso_clock
vdso/gettimeofday: Prepare do_hres_timens() for introduction of struct vdso_clock
vdso/gettimeofday: Prepare do_hres() for introduction of struct vdso_clock
vdso/gettimeofday: Prepare introduction of struct vdso_clock
vdso/helpers: Prepare introduction of struct vdso_clock
vdso/datapage: Define vdso_clock to prepare for multiple PTP clocks
vdso: Make vdso_time_data cacheline aligned
arm64: Make asm/cache.h compatible with vDSO
...
hrtimers are initialized with hrtimer_init() and a subsequent store to
the callback pointer. This turned out to be suboptimal for the upcoming
Rust integration and is obviously a silly implementation to begin with.
This cleanup replaces the hrtimer_init(T); T->function = cb; sequence
with hrtimer_setup(T, cb);
The conversion was done with Coccinelle and a few manual fixups.
Once the conversion has completely landed in mainline, hrtimer_init()
will be removed and the hrtimer::function becomes a private member.
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Merge tag 'timers-cleanups-2025-03-23' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull timer cleanups from Thomas Gleixner:
"A treewide hrtimer timer cleanup
hrtimers are initialized with hrtimer_init() and a subsequent store to
the callback pointer. This turned out to be suboptimal for the
upcoming Rust integration and is obviously a silly implementation to
begin with.
This cleanup replaces the hrtimer_init(T); T->function = cb; sequence
with hrtimer_setup(T, cb);
The conversion was done with Coccinelle and a few manual fixups.
Once the conversion has completely landed in mainline, hrtimer_init()
will be removed and the hrtimer::function becomes a private member"
* tag 'timers-cleanups-2025-03-23' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (100 commits)
wifi: rt2x00: Switch to use hrtimer_update_function()
io_uring: Use helper function hrtimer_update_function()
serial: xilinx_uartps: Use helper function hrtimer_update_function()
ASoC: fsl: imx-pcm-fiq: Switch to use hrtimer_setup()
RDMA: Switch to use hrtimer_setup()
virtio: mem: Switch to use hrtimer_setup()
drm/vmwgfx: Switch to use hrtimer_setup()
drm/xe/oa: Switch to use hrtimer_setup()
drm/vkms: Switch to use hrtimer_setup()
drm/msm: Switch to use hrtimer_setup()
drm/i915/request: Switch to use hrtimer_setup()
drm/i915/uncore: Switch to use hrtimer_setup()
drm/i915/pmu: Switch to use hrtimer_setup()
drm/i915/perf: Switch to use hrtimer_setup()
drm/i915/gvt: Switch to use hrtimer_setup()
drm/i915/huc: Switch to use hrtimer_setup()
drm/amdgpu: Switch to use hrtimer_setup()
stm class: heartbeat: Switch to use hrtimer_setup()
i2c: Switch to use hrtimer_setup()
iio: Switch to use hrtimer_setup()
...
- Fix a memory ordering issue in posix-timers
Posix-timer lookup is lockless and reevaluates the timer validity under
the timer lock, but the update which validates the timer is not
protected by the timer lock. That allows the store to be reordered
against the initialization stores, so that the lookup side can observe
a partially initialized timer. That's mostly a theoretical problem, but
incorrect nevertheless.
- Fix a long standing inconsistency of the coarse time getters
The coarse time getters read the base time of the current update cycle
without reading the actual hardware clock. NTP frequency adjustment can
set the base time backwards. The fine grained interfaces compensate
this by reading the clock and applying the new conversion factor, but
the coarse grained time getters use the base time directly. That allows
the user to observe time going backwards.
Cure it by always forwarding base time, when NTP changes the frequency
with an immediate step.
- Rework of posix-timer hashing
The posix-timer hash is not scalable and due to the CRIU timer restore
mechanism prone to massive contention on the global hash bucket lock.
Replace the global hash lock with a fine grained per bucket locking
scheme to address that.
- Rework the proc/$PID/timers interface.
/proc/$PID/timers is provided for CRIU to be able to restore a
timer. The printout happens with sighand lock held and interrupts
disabled. That's not required as this can be done with RCU protection
as well.
- Provide a sane mechanism for CRIU to restore a timer ID
CRIU restores timers by creating and deleting them until the kernel
internal per process ID counter reached the requested ID. That's
horribly slow for sparse timer IDs.
Provide a prctl() which allows CRIU to restore a timer with a given
ID. When enabled the ID pointer is used as input pointer to read the
requested ID from user space. When disabled, the normal allocation
scheme (next ID) is active as before. This is backwards compatible for
both kernel and user space.
- Make hrtimer_update_function() less expensive.
The sanity checks are valuable, but expensive for high frequency usage
in io/uring. Make the debug checks conditional and enable them only
when lockdep is enabled.
- Small updates, cleanups and improvements
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Merge tag 'timers-core-2025-03-23' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull timer core updates from Thomas Gleixner:
- Fix a memory ordering issue in posix-timers
Posix-timer lookup is lockless and reevaluates the timer validity
under the timer lock, but the update which validates the timer is not
protected by the timer lock. That allows the store to be reordered
against the initialization stores, so that the lookup side can
observe a partially initialized timer. That's mostly a theoretical
problem, but incorrect nevertheless.
- Fix a long standing inconsistency of the coarse time getters
The coarse time getters read the base time of the current update
cycle without reading the actual hardware clock. NTP frequency
adjustment can set the base time backwards. The fine grained
interfaces compensate this by reading the clock and applying the new
conversion factor, but the coarse grained time getters use the base
time directly. That allows the user to observe time going backwards.
Cure it by always forwarding base time, when NTP changes the
frequency with an immediate step.
- Rework of posix-timer hashing
The posix-timer hash is not scalable and due to the CRIU timer
restore mechanism prone to massive contention on the global hash
bucket lock.
Replace the global hash lock with a fine grained per bucket locking
scheme to address that.
- Rework the proc/$PID/timers interface.
/proc/$PID/timers is provided for CRIU to be able to restore a timer.
The printout happens with sighand lock held and interrupts disabled.
That's not required as this can be done with RCU protection as well.
- Provide a sane mechanism for CRIU to restore a timer ID
CRIU restores timers by creating and deleting them until the kernel
internal per process ID counter reached the requested ID. That's
horribly slow for sparse timer IDs.
Provide a prctl() which allows CRIU to restore a timer with a given
ID. When enabled the ID pointer is used as input pointer to read the
requested ID from user space. When disabled, the normal allocation
scheme (next ID) is active as before. This is backwards compatible
for both kernel and user space.
- Make hrtimer_update_function() less expensive.
The sanity checks are valuable, but expensive for high frequency
usage in io/uring. Make the debug checks conditional and enable them
only when lockdep is enabled.
- Small updates, cleanups and improvements
* tag 'timers-core-2025-03-23' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (27 commits)
selftests/timers: Improve skew_consistency by testing with other clockids
timekeeping: Fix possible inconsistencies in _COARSE clockids
posix-timers: Drop redundant memset() invocation
selftests/timers/posix-timers: Add a test for exact allocation mode
posix-timers: Provide a mechanism to allocate a given timer ID
posix-timers: Dont iterate /proc/$PID/timers with sighand:: Siglock held
posix-timers: Make per process list RCU safe
posix-timers: Avoid false cacheline sharing
posix-timers: Switch to jhash32()
posix-timers: Improve hash table performance
posix-timers: Make signal_struct:: Next_posix_timer_id an atomic_t
posix-timers: Make lock_timer() use guard()
posix-timers: Rework timer removal
posix-timers: Simplify lock/unlock_timer()
posix-timers: Use guards in a few places
posix-timers: Remove SLAB_PANIC from kmem cache
posix-timers: Remove a few paranoid warnings
posix-timers: Cleanup includes
posix-timers: Add cond_resched() to posix_timer_add() search loop
posix-timers: Initialise timer before adding it to the hash table
...
CONFIG_TRACE_BRANCH_PROFILING inserts a call to ftrace_likely_update()
for each use of likely() or unlikely(). That breaks noinstr rules if
the affected function is annotated as noinstr.
Disable branch profiling for files with noinstr functions. In addition
to some individual files, this also includes the entire arch/x86
subtree, as well as the kernel/entry, drivers/cpuidle, and drivers/idle
directories, all of which are noinstr-heavy.
Due to the nature of how sched binaries are built by combining multiple
.c files into one, branch profiling is disabled more broadly across the
sched code than would otherwise be needed.
This fixes many warnings like the following:
vmlinux.o: warning: objtool: do_syscall_64+0x40: call to ftrace_likely_update() leaves .noinstr.text section
vmlinux.o: warning: objtool: __rdgsbase_inactive+0x33: call to ftrace_likely_update() leaves .noinstr.text section
vmlinux.o: warning: objtool: handle_bug.isra.0+0x198: call to ftrace_likely_update() leaves .noinstr.text section
...
Reported-by: Ingo Molnar <mingo@kernel.org>
Suggested-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: https://lore.kernel.org/r/fb94fc9303d48a5ed370498f54500cc4c338eb6d.1742586676.git.jpoimboe@kernel.org
Lei Chen raised an issue with CLOCK_MONOTONIC_COARSE seeing time
inconsistencies.
Lei tracked down that this was being caused by the adjustment
tk->tkr_mono.xtime_nsec -= offset;
which is made to compensate for the unaccumulated cycles in offset when the
multiplicator is adjusted forward, so that the non-_COARSE clockids don't
see inconsistencies.
However, the _COARSE clockid getter functions use the adjusted xtime_nsec
value directly and do not compensate the negative offset via the
clocksource delta multiplied with the new multiplicator. In that case the
caller can observe time going backwards in consecutive calls.
By design, this negative adjustment should be fine, because the logic run
from timekeeping_adjust() is done after it accumulated approximately
multiplicator * interval_cycles
into xtime_nsec. The accumulated value is always larger then the
mult_adj * offset
value, which is subtracted from xtime_nsec. Both operations are done
together under the tk_core.lock, so the net change to xtime_nsec is always
always be positive.
However, do_adjtimex() calls into timekeeping_advance() as well, to to
apply the NTP frequency adjustment immediately. In this case,
timekeeping_advance() does not return early when the offset is smaller then
interval_cycles. In that case there is no time accumulated into
xtime_nsec. But the subsequent call into timekeeping_adjust(), which
modifies the multiplicator, subtracts from xtime_nsec to correct
for the new multiplicator.
Here because there was no accumulation, xtime_nsec becomes smaller than
before, which opens a window up to the next accumulation, where the _COARSE
clockid getters, which don't compensate for the offset, can observe the
inconsistency.
To fix this, rework the timekeeping_advance() logic so that when invoked
from do_adjtimex(), the time is immediately forwarded to accumulate also
the sub-interval portion into xtime. That means the remaining offset
becomes zero and the subsequent multiplier adjustment therefore does not
modify xtime_nsec.
There is another related inconsistency. If xtime is forwarded due to the
instantaneous multiplier adjustment, the NTP error, which was accumulated
with the previous setting, becomes meaningless.
Therefore clear the NTP error as well, after forwarding the clock for the
instantaneous multiplier update.
Fixes: da15cfdae0 ("time: Introduce CLOCK_REALTIME_COARSE")
Reported-by: Lei Chen <lei.chen@smartx.com>
Signed-off-by: John Stultz <jstultz@google.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/20250320200306.1712599-1-jstultz@google.com
Closes: https://lore.kernel.org/lkml/20250310030004.3705801-1-lei.chen@smartx.com/
Initially in commit 6891c4509c memset() was required to clear a variable
allocated on stack. Commit 2482097c6c removed the on stack variable and
retained the memset() despite the fact that the memory is allocated via
kmem_cache_zalloc() and therefore zereoed already.
Drop the redundant memset().
Signed-off-by: Cyrill Gorcunov <gorcunov@gmail.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/Z9ctVxwaYOV4A2g4@grain
Checkpoint/Restore in Userspace (CRIU) requires to reconstruct posix timers
with the same timer ID on restore. It uses sys_timer_create() and relies on
the monotonic increasing timer ID provided by this syscall. It creates and
deletes timers until the desired ID is reached. This is can loop for a long
time, when the checkpointed process had a very sparse timer ID range.
It has been debated to implement a new syscall to allow the creation of
timers with a given timer ID, but that's tideous due to the 32/64bit compat
issues of sigevent_t and of dubious value.
The restore mechanism of CRIU creates the timers in a state where all
threads of the restored process are held on a barrier and cannot issue
syscalls. That means the restorer task has exclusive control.
This allows to address this issue with a prctl() so that the restorer
thread can do:
if (prctl(PR_TIMER_CREATE_RESTORE_IDS, PR_TIMER_CREATE_RESTORE_IDS_ON))
goto linear_mode;
create_timers_with_explicit_ids();
prctl(PR_TIMER_CREATE_RESTORE_IDS, PR_TIMER_CREATE_RESTORE_IDS_OFF);
This is backwards compatible because the prctl() fails on older kernels and
CRIU can fall back to the linear timer ID mechanism. CRIU versions which do
not know about the prctl() just work as before.
Implement the prctl() and modify timer_create() so that it copies the
requested timer ID from userspace by utilizing the existing timer_t
pointer, which is used to copy out the allocated timer ID on success.
If the prctl() is disabled, which it is by default, timer_create() works as
before and does not try to read from the userspace pointer.
There is no problem when a broken or rogue user space application enables
the prctl(). If the user space pointer does not contain a valid ID, then
timer_create() fails. If the data is not initialized, but constains a
random valid ID, timer_create() will create that random timer ID or fail if
the ID is already given out.
As CRIU must use the raw syscall to avoid manipulating the internal state
of the restored process, this has no library dependencies and can be
adopted by CRIU right away.
Recreating two timers with IDs 1000000 and 2000000 takes 1.5 seconds with
the create/delete method. With the prctl() it takes 3 microseconds.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Reviewed-by: Cyrill Gorcunov <gorcunov@gmail.com>
Tested-by: Cyrill Gorcunov <gorcunov@gmail.com>
Link: https://lore.kernel.org/all/87jz8vz0en.ffs@tglx
Preparatory change to remove the sighand locking from the /proc/$PID/timers
iterator.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Link: https://lore.kernel.org/all/20250308155624.403223080@linutronix.de
struct k_itimer has the hlist_node, which is used for lookup in the hash
bucket, and the timer lock in the same cache line.
That's obviously bad, if one CPU fiddles with a timer and the other is
walking the hash bucket on which that timer is queued.
Avoid this by restructuring struct k_itimer, so that the read mostly (only
modified during setup and teardown) fields are in the first cache line and
the lock and the rest of the fields which get written to are in cacheline
2-N.
Reduces cacheline contention in a test case of 64 processes creating and
accessing 20000 timers each by almost 30% according to perf.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Link: https://lore.kernel.org/all/20250308155624.341108067@linutronix.de
The hash distribution of hash_32() is suboptimal. jhash32() provides a way
better distribution, which evens out the length of the hash bucket lists,
which in turn avoids large outliers in list walk times.
Due to the sparse ID space (thanks CRIU) there is no guarantee that the
timers will be fully evenly distributed over the hash buckets, but the
behaviour is way better than with hash_32() even for randomly sparse ID
spaces.
For a pathological test case with 64 processes creating and accessing
20000 timers each, this results in a runtime reduction of ~10% and a
significantly reduced runtime variation.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/20250308155624.279080328@linutronix.de
Eric and Ben reported a significant performance bottleneck on the global
hash, which is used to store posix timers for lookup.
Eric tried to do a lockless validation of a new timer ID before trying to
insert the timer, but that does not solve the problem.
For the non-contended case this is a pointless exercise and for the
contended case this extra lookup just creates enough interleaving that all
tasks can make progress.
There are actually two real solutions to the problem:
1) Provide a per process (signal struct) xarray storage
2) Implement a smarter hash like the one in the futex code
#1 works perfectly fine for most cases, but the fact that CRIU enforced a
linear increasing timer ID to restore timers makes this problematic.
It's easy enough to create a sparse timer ID space, which amounts very
fast to a large junk of memory consumed for the xarray. 2048 timers with
a ID offset of 512 consume more than one megabyte of memory for the
xarray storage.
#2 The main advantage of the futex hash is that it uses per hash bucket
locks instead of a global hash lock. Aside of that it is scaled
according to the number of CPUs at boot time.
Experiments with artifical benchmarks have shown that a scaled hash with
per bucket locks comes pretty close to the xarray performance and in some
scenarios it performes better.
Test 1:
A single process creates 20000 timers and afterwards invokes
timer_getoverrun(2) on each of them:
mainline Eric newhash xarray
create 23 ms 23 ms 9 ms 8 ms
getoverrun 14 ms 14 ms 5 ms 4 ms
Test 2:
A single process creates 50000 timers and afterwards invokes
timer_getoverrun(2) on each of them:
mainline Eric newhash xarray
create 98 ms 219 ms 20 ms 18 ms
getoverrun 62 ms 62 ms 10 ms 9 ms
Test 3:
A single process creates 100000 timers and afterwards invokes
timer_getoverrun(2) on each of them:
mainline Eric newhash xarray
create 313 ms 750 ms 48 ms 33 ms
getoverrun 261 ms 260 ms 20 ms 14 ms
Erics changes create quite some overhead in the create() path due to the
double list walk, as the main issue according to perf is the list walk
itself. With 100k timers each hash bucket contains ~200 timers, which in
the worst case need to be all inspected. The same problem applies for
getoverrun() where the lookup has to walk through the hash buckets to find
the timer it is looking for.
The scaled hash obviously reduces hash collisions and lock contention
significantly. This becomes more prominent with concurrency.
Test 4:
A process creates 63 threads and all threads wait on a barrier before
each instance creates 20000 timers and afterwards invokes
timer_getoverrun(2) on each of them. The threads are pinned on
seperate CPUs to achive maximum concurrency. The numbers are the
average times per thread:
mainline Eric newhash xarray
create 180239 ms 38599 ms 579 ms 813 ms
getoverrun 2645 ms 2642 ms 32 ms 7 ms
Test 5:
A process forks 63 times and all forks wait on a barrier before each
instance creates 20000 timers and afterwards invokes
timer_getoverrun(2) on each of them. The processes are pinned on
seperate CPUs to achive maximum concurrency. The numbers are the
average times per process:
mainline eric newhash xarray
create 157253 ms 40008 ms 83 ms 60 ms
getoverrun 2611 ms 2614 ms 40 ms 4 ms
So clearly the reduction of lock contention with Eric's changes makes a
significant difference for the create() loop, but it does not mitigate the
problem of long list walks, which is clearly visible on the getoverrun()
side because that is purely dominated by the lookup itself. Once the timer
is found, the syscall just reads from the timer structure with no other
locks or code paths involved and returns.
The reason for the difference between the thread and the fork case for the
new hash and the xarray is that both suffer from contention on
sighand::siglock and the xarray suffers additionally from contention on the
xarray lock on insertion.
The only case where the reworked hash slighly outperforms the xarray is a
tight loop which creates and deletes timers.
Test 4:
A process creates 63 threads and all threads wait on a barrier before
each instance runs a loop which creates and deletes a timer 100000
times in a row. The threads are pinned on seperate CPUs to achive
maximum concurrency. The numbers are the average times per thread:
mainline Eric newhash xarray
loop 5917 ms 5897 ms 5473 ms 7846 ms
Test 5:
A process forks 63 times and all forks wait on a barrier before each
each instance runs a loop which creates and deletes a timer 100000
times in a row. The processes are pinned on seperate CPUs to achive
maximum concurrency. The numbers are the average times per process:
mainline Eric newhash xarray
loop 5137 ms 7828 ms 891 ms 872 ms
In both test there is not much contention on the hash, but the ucount
accounting for the signal and in the thread case the sighand::siglock
contention (plus the xarray locking) contribute dominantly to the overhead.
As the memory consumption of the xarray in the sparse ID case is
significant, the scaled hash with per bucket locks seems to be the better
overall option. While the xarray has faster lookup times for a large number
of timers, the actual syscall usage, which requires the lookup is not an
extreme hotpath. Most applications utilize signal delivery and all syscalls
except timer_getoverrun(2) are all but cheap.
So implement a scaled hash with per bucket locks, which offers the best
tradeoff between performance and memory consumption.
Reported-by: Eric Dumazet <edumazet@google.com>
Reported-by: Benjamin Segall <bsegall@google.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Frederic Weisbecker <frederic@kernel.org>
Link: https://lore.kernel.org/all/20250308155624.216091571@linutronix.de
The global hash_lock protecting the posix timer hash table can be heavily
contended especially when there is an extensive linear search for a timer
ID.
Timer IDs are handed out by monotonically increasing next_posix_timer_id
and then validating that there is no timer with the same ID in the hash
table. Both operations happen with the global hash lock held.
To reduce the hash lock contention the hash will be reworked to a scaled
hash with per bucket locks, which requires to handle the ID counter
lockless.
Prepare for this by making next_posix_timer_id an atomic_t, which can be
used lockless with atomic_inc_return().
[ tglx: Adopted from Eric's series, massaged change log and simplified it ]
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Acked-by: Frederic Weisbecker <frederic@kernel.org>
Link: https://lore.kernel.org/all/20250219125522.2535263-2-edumazet@google.com
Link: https://lore.kernel.org/all/20250308155624.151545978@linutronix.de
The lookup and locking of posix timers requires the same repeating pattern
at all usage sites:
tmr = lock_timer(tiner_id);
if (!tmr)
return -EINVAL;
....
unlock_timer(tmr);
Solve this with a guard implementation, which works in most places out of
the box except for those, which need to unlock the timer inside the guard
scope.
Though the only places where this matters are timer_delete() and
timer_settime(). In both cases the timer pointer needs to be preserved
across the end of the scope, which is solved by storing the pointer in a
variable outside of the scope.
timer_settime() also has to protect the timer with RCU before unlocking,
which obviously can't use guard(rcu) before leaving the guard scope as that
guard is cleaned up before the unlock. Solve this by providing the RCU
protection open coded.
[ tglx: Made it work and added change log ]
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Frederic Weisbecker <frederic@kernel.org>
Link: https://lore.kernel.org/all/20250224162103.GD11590@noisy.programming.kicks-ass.net
Link: https://lore.kernel.org/all/20250308155624.087465658@linutronix.de
sys_timer_delete() and the do_exit() cleanup function itimer_delete() are
doing the same thing, but have needlessly different implementations instead
of sharing the code.
The other oddity of timer deletion is the fact that the timer is not
invalidated before the actual deletion happens, which allows concurrent
lookups to succeed.
That's wrong because a timer which is in the process of being deleted
should not be visible and any actions like signal queueing, delivery and
rearming should not happen once the task, which invoked timer_delete(), has
the timer locked.
Rework the code so that:
1) The signal queueing and delivery code ignore timers which are marked
invalid
2) The deletion implementation between sys_timer_delete() and
itimer_delete() is shared
3) The timer is invalidated and removed from the linked lists before
the deletion callback of the relevant clock is invoked.
That requires to rework timer_wait_running() as it does a lookup of
the timer when relocking it at the end. In case of deletion this
lookup would fail due to the preceding invalidation and the wait loop
would terminate prematurely.
But due to the preceding invalidation the timer cannot be accessed by
other tasks anymore, so there is no way that the timer has been freed
after the timer lock has been dropped.
Move the re-validation out of timer_wait_running() and handle it at
the only other usage site, timer_settime().
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Link: https://lore.kernel.org/all/87zfht1exf.ffs@tglx
Since the integration of sigqueue into the timer struct, lock_timer() is
only used in task context. So taking the lock with irqsave() is not longer
required.
Convert it to use spin_[un]lock_irq().
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Link: https://lore.kernel.org/all/20250308155623.959825668@linutronix.de
There is no need to panic when the posix-timer kmem_cache can't be
created. timer_create() will fail with -ENOMEM and that's it.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Link: https://lore.kernel.org/all/20250308155623.829215801@linutronix.de
Warnings about a non-initialized timer or non-existing callbacks are just
useful for implementing new posix clocks, but there a NULL pointer
dereference is expected anyway. :)
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Link: https://lore.kernel.org/all/20250308155623.765462334@linutronix.de
A timer is only valid in the hashtable when both timer::it_signal and
timer::it_id are set to their final values, but timers are added without
those values being set.
The timer ID is allocated when the timer is added to the hash in invalid
state. The ID is taken from a monotonically increasing per process counter
which wraps around after reaching INT_MAX. The hash insertion validates
that there is no timer with the allocated ID in the hash table which
belongs to the same process. That opens a mostly theoretical race condition:
If other threads of the same process manage to create/delete timers in
rapid succession before the newly created timer is fully initialized and
wrap around to the timer ID which was handed out, then a duplicate timer ID
will be inserted into the hash table.
Prevent this by:
1) Setting timer::it_id before inserting the timer into the hashtable.
2) Storing the signal pointer in timer::it_signal with bit 0 set before
inserting it into the hashtable.
Bit 0 acts as a invalid bit, which means that the regular lookup for
sys_timer_*() will fail the comparison with the signal pointer.
But the lookup on insertion masks out bit 0 and can therefore detect a
timer which is not yet valid, but allocated in the hash table. Bit 0
in the pointer is cleared once the initialization of the timer
completed.
[ tglx: Fold ID and signal iniitializaion into one patch and massage change
log and comments. ]
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Link: https://lore.kernel.org/all/20250219125522.2535263-3-edumazet@google.com
Link: https://lore.kernel.org/all/20250308155623.572035178@linutronix.de
Frederic pointed out that the memory operations to initialize the timer are
not guaranteed to be visible, when __lock_timer() observes timer::it_signal
valid under timer::it_lock:
T0 T1
--------- -----------
do_timer_create()
// A
new_timer->.... = ....
spin_lock(current->sighand)
// B
WRITE_ONCE(new_timer->it_signal, current->signal)
spin_unlock(current->sighand)
sys_timer_*()
t = __lock_timer()
spin_lock(&timr->it_lock)
// observes B
if (timr->it_signal == current->signal)
return timr;
if (!t)
return;
// Is not guaranteed to observe A
Protect the write of timer::it_signal, which makes the timer valid, with
timer::it_lock as well. This guarantees that T1 must observe the
initialization A completely, when it observes the valid signal pointer
under timer::it_lock. sighand::siglock must still be taken to protect the
signal::posix_timers list.
Reported-by: Frederic Weisbecker <frederic@kernel.org>
Suggested-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Link: https://lore.kernel.org/all/20250308155623.507944489@linutronix.de
The size argument of strscpy() is only required when the destination
pointer is not a fixed sized array or when the copy needs to be smaller
than the size of the fixed sized destination array.
For fixed sized destination arrays and full copies, strscpy() automatically
determines the length of the destination buffer if the size argument is
omitted.
This makes the explicit sizeof() unnecessary. Remove it.
[ tglx: Massaged change log ]
Signed-off-by: Thorsten Blum <thorsten.blum@linux.dev>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/20250311110624.495718-2-thorsten.blum@linux.dev
This reverts commit f590308536 ("timer debug: Hide kernel addresses via
%pK in /proc/timer_list")
The timer list helper SEQ_printf() uses either the real seq_printf() for
procfs output or vprintk() to print to the kernel log, when invoked from
SysRq-q. It uses %pK for printing pointers.
In the past %pK was prefered over %p as it would not leak raw pointer
values into the kernel log. Since commit ad67b74d24 ("printk: hash
addresses printed with %p") the regular %p has been improved to avoid this
issue.
Furthermore, restricted pointers ("%pK") were never meant to be used
through printk(). They can still unintentionally leak raw pointers or
acquire sleeping looks in atomic contexts.
Switch to the regular pointer formatting which is safer, easier to reason
about and sufficient here.
Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/lkml/20250113171731-dc10e3c1-da64-4af0-b767-7c7070468023@linutronix.de/
Link: https://lore.kernel.org/all/20250311-restricted-pointers-timer-v1-1-6626b91e54ab@linutronix.de
To support multiple PTP clocks, the VDSO data structure needs to be
reworked. All clock specific data will end up in struct vdso_clock and in
struct vdso_time_data there will be an array of VDSO clocks.
Now that all preparatory changes are in place:
Split the clock related struct members into a separate struct
vdso_clock. Make sure all users are aware, that vdso_time_data is no longer
initialized as an array and vdso_clock is now the array inside
vdso_data. Remove the vdso_clock define, which mapped it to vdso_time_data
for the transition.
Signed-off-by: Anna-Maria Behnsen <anna-maria@linutronix.de>
Signed-off-by: Nam Cao <namcao@linutronix.de>
Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/20250303-vdso-clock-v1-19-c1b5c69a166f@linutronix.de
To support multiple PTP clocks, the VDSO data structure needs to be
reworked. All clock specific data will end up in struct vdso_clock and in
struct vdso_time_data there will be array of VDSO clocks. At the moment,
vdso_clock is simply a define which maps vdso_clock to vdso_time_data.
To prepare for the rework of the data structures, replace the struct
vdso_time_data pointer with a struct vdso_clock pointer where applicable.
No functional change.
Signed-off-by: Anna-Maria Behnsen <anna-maria@linutronix.de>
Signed-off-by: Nam Cao <namcao@linutronix.de>
Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/20250303-vdso-clock-v1-14-c1b5c69a166f@linutronix.de
To support multiple PTP clocks, the VDSO data structure needs to be
reworked. All clock specific data will end up in struct vdso_clock and in
struct vdso_time_data there will be array of VDSO clocks. At the moment,
vdso_clock is simply a define which maps vdso_clock to vdso_time_data.
For time namespaces, vdso_time_data needs to be set up. But only the clock
related part of the vdso_data thats requires this setup. To reflect the
future struct vdso_clock, rename timens_setup_vdso_data() to
timns_setup_vdso_clock_data().
No functional change.
Signed-off-by: Anna-Maria Behnsen <anna-maria@linutronix.de>
Signed-off-by: Nam Cao <namcao@linutronix.de>
Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/20250303-vdso-clock-v1-13-c1b5c69a166f@linutronix.de
To support multiple PTP clocks, the VDSO data structure needs to be
reworked. All clock specific data will end up in struct vdso_clock and in
struct vdso_time_data there will be array of VDSO clocks. At the moment,
vdso_clock is simply a define which maps vdso_clock to vdso_time_data.
To prepare for the rework of the data structures, replace the struct
vdso_time_data pointer with a struct vdso_clock pointer where applicable.
No functional change.
Signed-off-by: Anna-Maria Behnsen <anna-maria@linutronix.de>
Signed-off-by: Nam Cao <namcao@linutronix.de>
Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/20250303-vdso-clock-v1-12-c1b5c69a166f@linutronix.de
Many devices implement highly accurate clocks, which the kernel manages
as PTP Hardware Clocks (PHCs). Userspace applications rely on these
clocks to timestamp events, trace workload execution, correlate
timescales across devices, and keep various clocks in sync.
The kernel’s current implementation of PTP clocks does not enforce file
permissions checks for most device operations except for POSIX clock
operations, where file mode is verified in the POSIX layer before
forwarding the call to the PTP subsystem. Consequently, it is common
practice to not give unprivileged userspace applications any access to
PTP clocks whatsoever by giving the PTP chardevs 600 permissions. An
example of users running into this limitation is documented in [1].
Additionally, POSIX layer requires WRITE permission even for readonly
adjtime() calls which are used in PTP layer to return current frequency
offset applied to the PHC.
Add permission checks for functions that modify the state of a PTP
device. Continue enforcing permission checks for POSIX clock operations
(settime, adjtime) in the POSIX layer. Only require WRITE access for
dynamic clocks adjtime() if any flags are set in the modes field.
[1] https://lists.nwtime.org/sympa/arc/linuxptp-users/2024-01/msg00036.html
Changes in v4:
- Require FMODE_WRITE in ajtime() only for calls modifying the clock in
any way.
Acked-by: Richard Cochran <richardcochran@gmail.com>
Reviewed-by: Vadim Fedorenko <vadim.fedorenko@linux.dev>
Signed-off-by: Wojtek Wasko <wwasko@nvidia.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: David S. Miller <davem@davemloft.net>
File descriptor based pc_clock_*() operations of dynamic posix clocks
have access to the file pointer and implement permission checks in the
generic code before invoking the relevant dynamic clock callback.
Character device operations (open, read, poll, ioctl) do not implement a
generic permission control and the dynamic clock callbacks have no
access to the file pointer to implement them.
Extend struct posix_clock_context with a struct file pointer and
initialize it in posix_clock_open(), so that all dynamic clock callbacks
can access it.
Acked-by: Richard Cochran <richardcochran@gmail.com>
Reviewed-by: Vadim Fedorenko <vadim.fedorenko@linux.dev>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Wojtek Wasko <wwasko@nvidia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
The normal and compat ioctl handlers are identical,
which is fine as compat ioctls are detected and handled dynamically
inside the underlying clock implementation.
The duplicate definition however is unnecessary.
Just reuse the regular ioctl handler also for compat ioctls.
Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Cyrill Gorcunov <gorcunov@gmail.com>
Link: https://lore.kernel.org/all/20250225-posix-clock-compat-cleanup-v2-1-30de86457a2b@weissschuh.net
All users of the time releated parts of the vDSO are now using the generic
storage implementation. Remove the therefore unnecessary compatibility
accessor functions and symbols.
Co-developed-by: Nam Cao <namcao@linutronix.de>
Signed-off-by: Nam Cao <namcao@linutronix.de>
Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/20250204-vdso-store-rng-v3-18-13a4669dfc8c@linutronix.de
Historically each architecture defined their own way to store the vDSO
data page. Add a generic mechanism to provide storage for that page.
Furthermore this generic storage will be extended to also provide
uniform storage for *non*-time-related data, like the random state or
architecture-specific data. These will have their own pages and data
structures, so rename 'vdso_data' into 'vdso_time_data' to make that
split clear from the name.
Also introduce a new consistent naming scheme for the symbols related to
the vDSO, which makes it clear if the symbol is accessible from
userspace or kernel space and the type of data behind the symbol.
The generic fault handler contains an optimization to prefault the vvar
page when the timens page is accessed. This was lifted from s390 and x86.
Co-developed-by: Nam Cao <namcao@linutronix.de>
Signed-off-by: Nam Cao <namcao@linutronix.de>
Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/20250204-vdso-store-rng-v3-5-13a4669dfc8c@linutronix.de
hrtimer_setup() takes the callback function pointer as argument and
initializes the timer completely.
Replace hrtimer_init() and the open coded initialization of
hrtimer::function with the new setup mechanism.
Most of this patch is generated by Coccinelle. Except for the TX thrtimer
in bcm_tx_setup() because this timer is not used and the callback function
is never set. For this particular case, set the callback to
hrtimer_dummy_timeout()
Signed-off-by: Nam Cao <namcao@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Marc Kleine-Budde <mkl@pengutronix.de>
Link: https://lore.kernel.org/all/a3a6be42c818722ad41758457408a32163bfd9a0.1738746872.git.namcao@linutronix.de
hrtimer_setup() takes the callback function pointer as argument and
initializes the timer completely.
Replace hrtimer_init() and the open coded initialization of
hrtimer::function with the new setup mechanism.
Signed-off-by: Nam Cao <namcao@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/170bb691a0d59917c8268a98c80b607128fc9f7f.1738746821.git.namcao@linutronix.de
exit_itimers() loops through every timer in the process to delete it. This
requires taking the system-wide hash_lock for each of these timers, and
contends with other processes trying to create or delete timers.
When a process creates hundreds of thousands of timers, and then exits
while other processes contend with it, this can trigger softlockups on
CONFIG_PREEMPT=n.
Add a cond_resched() invocation into the loop to allow the system to make
progress.
Signed-off-by: Ben Segall <bsegall@google.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/xm2634gg2n23.fsf@google.com
Clang and GCC complain about overlapped initialisers in the
hrtimer_clock_to_base_table definition. With `make W=1` and CONFIG_WERROR=y
(which is default nowadays) this breaks the build:
CC kernel/time/hrtimer.o
kernel/time/hrtimer.c:124:21: error: initializer overrides prior initialization of this subobject [-Werror,-Winitializer-overrides]
124 | [CLOCK_REALTIME] = HRTIMER_BASE_REALTIME,
kernel/time/hrtimer.c:122:27: note: previous initialization is here
122 | [0 ... MAX_CLOCKS - 1] = HRTIMER_MAX_CLOCK_BASES,
(and similar for CLOCK_MONOTONIC, CLOCK_BOOTTIME, and CLOCK_TAI).
hrtimer_clockid_to_base(), which uses the table, is only used in
__hrtimer_init(), which is not a hotpath.
Therefore replace the table lookup with a switch case in
hrtimer_clockid_to_base() to avoid this warning.
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/20250214134424.3367619-1-andriy.shevchenko@linux.intel.com
caused false positive warnings.
Also fix a timer migration setup bug when new CPUs are added.
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Merge tag 'timers-urgent-2025-02-08' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull timer fixes from Ingo Molnar:
"Fix a PREEMPT_RT bug in the clocksource verification code that caused
false positive warnings.
Also fix a timer migration setup bug when new CPUs are added"
* tag 'timers-urgent-2025-02-08' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
timers/migration: Fix off-by-one root mis-connection
clocksource: Use migrate_disable() to avoid calling get_random_u32() in atomic context
Before attaching a new root to the old root, the children counter of the
new root is checked to verify that only the upcoming CPU's top group have
been connected to it. However since the recently added commit b729cc1ec2
("timers/migration: Fix another race between hotplug and idle entry/exit")
this check is not valid anymore because the old root is pre-accounted
as a child to the new root. Therefore after connecting the upcoming
CPU's top group to the new root, the children count to be expected must
be 2 and not 1 anymore.
This omission results in the old root to not be connected to the new
root. Then eventually the system may run with more than one top level,
which defeats the purpose of a single idle migrator.
Also the old root is pre-accounted but not connected upon the new root
creation. But it can be connected to the new root later on. Therefore
the old root may be accounted twice to the new root. The propagation of
such overcommit can end up creating a double final top-level root with a
groupmask incorrectly initialized. Although harmless given that the final
top level roots will never have a parent to walk up to, this oddity
opportunistically reported the core issue:
WARNING: CPU: 8 PID: 0 at kernel/time/timer_migration.c:543 tmigr_requires_handle_remote
CPU: 8 UID: 0 PID: 0 Comm: swapper/8
RIP: 0010:tmigr_requires_handle_remote
Call Trace:
<IRQ>
? tmigr_requires_handle_remote
? hrtimer_run_queues
update_process_times
tick_periodic
tick_handle_periodic
__sysvec_apic_timer_interrupt
sysvec_apic_timer_interrupt
</IRQ>
Fix the problem by taking the old root into account in the children count
of the new root so the connection is not omitted.
Also warn when more than one top level group exists to better detect
similar issues in the future.
Fixes: b729cc1ec2 ("timers/migration: Fix another race between hotplug and idle entry/exit")
Reported-by: Matt Fleming <mfleming@cloudflare.com>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/all/20250205160220.39467-1-frederic@kernel.org
- Properly cast the input to secs_to_jiffies() to unsigned long as
otherwise the result uses the data type of the input variable, which
causes result range checks to fail if the input data type is signed and
smaller than unsigned long.
- Handle late armed hrtimers gracefully on CPU hotplug
There are legitimate cases where a hrtimer is (re)armed on an outgoing
CPU after the timers have been migrated away. This triggers warnings and
caused people to implement horrible workarounds in RCU. But those work
arounds are incomplete and do not cover e.g. the scheduler hrtimers.
Stop this by force moving timer which are enqueued on the current CPU
after timer migration to be queued on a remote online CPU.
This allows to undo the workarounds in a seperate step.
- Demote a warning level printk() to info level in the clocksource
watchdog code as there is no point to emit a warning level message for a
purely informational message.
- Mark a helper function __always_inline and move it into the existing
#ifdef block to avoid 'unused function' warnings from CLANG
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Merge tag 'timers-urgent-2025-02-03' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull timer fixes from Thomas Gleixner:
- Properly cast the input to secs_to_jiffies() to unsigned long as
otherwise the result uses the data type of the input variable, which
causes result range checks to fail if the input data type is signed
and smaller than unsigned long.
- Handle late armed hrtimers gracefully on CPU hotplug
There are legitimate cases where a hrtimer is (re)armed on an
outgoing CPU after the timers have been migrated away. This triggers
warnings and caused people to implement horrible workarounds in RCU.
But those workarounds are incomplete and do not cover e.g. the
scheduler hrtimers.
Stop this by force moving timer which are enqueued on the current CPU
after timer migration to be queued on a remote online CPU.
This allows to undo the workarounds in a seperate step.
- Demote a warning level printk() to info level in the clocksource
watchdog code as there is no point to emit a warning level message
for a purely informational message.
- Mark a helper function __always_inline and move it into the existing
#ifdef block to avoid 'unused function' warnings from CLANG
* tag 'timers-urgent-2025-02-03' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
jiffies: Cast to unsigned long in secs_to_jiffies() conversion
clocksource: Use pr_info() for "Checking clocksource synchronization" message
hrtimers: Force migrate away hrtimers queued after CPUHP_AP_HRTIMERS_DYING
hrtimers: Mark is_migration_base() with __always_inline
The following bug report happened with a PREEMPT_RT kernel:
BUG: sleeping function called from invalid context at kernel/locking/spinlock_rt.c:48
in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 2012, name: kwatchdog
preempt_count: 1, expected: 0
RCU nest depth: 0, expected: 0
get_random_u32+0x4f/0x110
clocksource_verify_choose_cpus+0xab/0x1a0
clocksource_verify_percpu.part.0+0x6b/0x330
clocksource_watchdog_kthread+0x193/0x1a0
It is due to the fact that clocksource_verify_choose_cpus() is invoked with
preemption disabled. This function invokes get_random_u32() to obtain
random numbers for choosing CPUs. The batched_entropy_32 local lock and/or
the base_crng.lock spinlock in driver/char/random.c will be acquired during
the call. In PREEMPT_RT kernel, they are both sleeping locks and so cannot
be acquired in atomic context.
Fix this problem by using migrate_disable() to allow smp_processor_id() to
be reliably used without introducing atomic context. preempt_disable() is
then called after clocksource_verify_choose_cpus() but before the
clocksource measurement is being run to avoid introducing unexpected
latency.
Fixes: 7560c02bdf ("clocksource: Check per-CPU clock synchronization when marked unstable")
Suggested-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Waiman Long <longman@redhat.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Paul E. McKenney <paulmck@kernel.org>
Reviewed-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Link: https://lore.kernel.org/all/20250131173323.891943-2-longman@redhat.com
Add the const qualifier to all the ctl_tables in the tree except for
watchdog_hardlockup_sysctl, memory_allocation_profiling_sysctls,
loadpin_sysctl_table and the ones calling register_net_sysctl (./net,
drivers/inifiniband dirs). These are special cases as they use a
registration function with a non-const qualified ctl_table argument or
modify the arrays before passing them on to the registration function.
Constifying ctl_table structs will prevent the modification of
proc_handler function pointers as the arrays would reside in .rodata.
This is made possible after commit 78eb4ea25c ("sysctl: treewide:
constify the ctl_table argument of proc_handlers") constified all the
proc_handlers.
Created this by running an spatch followed by a sed command:
Spatch:
virtual patch
@
depends on !(file in "net")
disable optional_qualifier
@
identifier table_name != {
watchdog_hardlockup_sysctl,
iwcm_ctl_table,
ucma_ctl_table,
memory_allocation_profiling_sysctls,
loadpin_sysctl_table
};
@@
+ const
struct ctl_table table_name [] = { ... };
sed:
sed --in-place \
-e "s/struct ctl_table .table = &uts_kern/const struct ctl_table *table = \&uts_kern/" \
kernel/utsname_sysctl.c
Reviewed-by: Song Liu <song@kernel.org>
Acked-by: Steven Rostedt (Google) <rostedt@goodmis.org> # for kernel/trace/
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com> # SCSI
Reviewed-by: Darrick J. Wong <djwong@kernel.org> # xfs
Acked-by: Jani Nikula <jani.nikula@intel.com>
Acked-by: Corey Minyard <cminyard@mvista.com>
Acked-by: Wei Liu <wei.liu@kernel.org>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Bill O'Donnell <bodonnel@redhat.com>
Acked-by: Baoquan He <bhe@redhat.com>
Acked-by: Ashutosh Dixit <ashutosh.dixit@intel.com>
Acked-by: Anna Schumaker <anna.schumaker@oracle.com>
Signed-off-by: Joel Granados <joel.granados@kernel.org>
The "Checking clocksource synchronization" message is normally printed
when clocksource_verify_percpu() is called for a given clocksource if
both the CLOCK_SOURCE_UNSTABLE and CLOCK_SOURCE_VERIFY_PERCPU flags
are set.
It is an informational message and so pr_info() is the correct choice.
Signed-off-by: Waiman Long <longman@redhat.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Paul E. McKenney <paulmck@kernel.org>
Acked-by: John Stultz <jstultz@google.com>
Link: https://lore.kernel.org/all/20250125015442.3740588-1-longman@redhat.com
hrtimers are migrated away from the dying CPU to any online target at
the CPUHP_AP_HRTIMERS_DYING stage in order not to delay bandwidth timers
handling tasks involved in the CPU hotplug forward progress.
However wakeups can still be performed by the outgoing CPU after
CPUHP_AP_HRTIMERS_DYING. Those can result again in bandwidth timers being
armed. Depending on several considerations (crystal ball power management
based election, earliest timer already enqueued, timer migration enabled or
not), the target may eventually be the current CPU even if offline. If that
happens, the timer is eventually ignored.
The most notable example is RCU which had to deal with each and every of
those wake-ups by deferring them to an online CPU, along with related
workarounds:
_ e787644caf (rcu: Defer RCU kthreads wakeup when CPU is dying)
_ 9139f93209 (rcu/nocb: Fix RT throttling hrtimer armed from offline CPU)
_ f7345ccc62 (rcu/nocb: Fix rcuog wake-up from offline softirq)
The problem isn't confined to RCU though as the stop machine kthread
(which runs CPUHP_AP_HRTIMERS_DYING) reports its completion at the end
of its work through cpu_stop_signal_done() and performs a wake up that
eventually arms the deadline server timer:
WARNING: CPU: 94 PID: 588 at kernel/time/hrtimer.c:1086 hrtimer_start_range_ns+0x289/0x2d0
CPU: 94 UID: 0 PID: 588 Comm: migration/94 Not tainted
Stopper: multi_cpu_stop+0x0/0x120 <- stop_machine_cpuslocked+0x66/0xc0
RIP: 0010:hrtimer_start_range_ns+0x289/0x2d0
Call Trace:
<TASK>
start_dl_timer
enqueue_dl_entity
dl_server_start
enqueue_task_fair
enqueue_task
ttwu_do_activate
try_to_wake_up
complete
cpu_stopper_thread
Instead of providing yet another bandaid to work around the situation, fix
it in the hrtimers infrastructure instead: always migrate away a timer to
an online target whenever it is enqueued from an offline CPU.
This will also allow to revert all the above RCU disgraceful hacks.
Fixes: 5c0930ccaa ("hrtimers: Push pending hrtimers away from outgoing CPU earlier")
Reported-by: Vlad Poenaru <vlad.wing@gmail.com>
Reported-by: Usama Arif <usamaarif642@gmail.com>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: stable@vger.kernel.org
Tested-by: Paul E. McKenney <paulmck@kernel.org>
Link: https://lore.kernel.org/all/20250117232433.24027-1-frederic@kernel.org
Closes: 20241213203739.1519801-1-usamaarif642@gmail.com
When is_migration_base() is unused, it prevents kernel builds
with clang, `make W=1` and CONFIG_WERROR=y:
kernel/time/hrtimer.c:156:20: error: unused function 'is_migration_base' [-Werror,-Wunused-function]
156 | static inline bool is_migration_base(struct hrtimer_clock_base *base)
| ^~~~~~~~~~~~~~~~~
Fix this by marking it with __always_inline.
[ tglx: Use __always_inline instead of __maybe_unused and move it into the
usage sites conditional ]
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/20250116160745.243358-1-andriy.shevchenko@linux.intel.com
- Just boring cleanups, typo and comment fixes and trivial optimizations
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Merge tag 'timers-core-2025-01-21' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull timer and timekeeping updates from Thomas Gleixner:
- Just boring cleanups, typo and comment fixes and trivial optimizations
* tag 'timers-core-2025-01-21' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
timers/migration: Simplify top level detection on group setup
timers: Optimize get_timer_[this_]cpu_base()
timekeeping: Remove unused ktime_get_fast_timestamps()
timer/migration: Fix kernel-doc warnings for union tmigr_state
tick/broadcast: Add kernel-doc for function parameters
hrtimers: Update the return type of enqueue_hrtimer()
clocksource/wdtest: Print time values for short udelay(1)
posix-timers: Fix typo in __lock_timer()
vdso: Correct typo in PAGE_SHIFT comment
Having a single group on a given level is enough to know this is the
top level, because a root has to have at least two children, unless that
root is the only group and the children are actual CPUs.
Simplify the test in tmigr_setup_groups() accordingly.
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/20250114231507.21672-5-frederic@kernel.org
Consider a scenario where a CPU transitions from CPUHP_ONLINE to halfway
through a CPU hotunplug down to CPUHP_HRTIMERS_PREPARE, and then back to
CPUHP_ONLINE:
Since hrtimers_prepare_cpu() does not run, cpu_base.hres_active remains set
to 1 throughout. However, during a CPU unplug operation, the tick and the
clockevents are shut down at CPUHP_AP_TICK_DYING. On return to the online
state, for instance CFS incorrectly assumes that the hrtick is already
active, and the chance of the clockevent device to transition to oneshot
mode is also lost forever for the CPU, unless it goes back to a lower state
than CPUHP_HRTIMERS_PREPARE once.
This round-trip reveals another issue; cpu_base.online is not set to 1
after the transition, which appears as a WARN_ON_ONCE in enqueue_hrtimer().
Aside of that, the bulk of the per CPU state is not reset either, which
means there are dangling pointers in the worst case.
Address this by adding a corresponding startup() callback, which resets the
stale per CPU state and sets the online flag.
[ tglx: Make the new callback unconditionally available, remove the online
modification in the prepare() callback and clear the remaining
state in the starting callback instead of the prepare callback ]
Fixes: 5c0930ccaa ("hrtimers: Push pending hrtimers away from outgoing CPU earlier")
Signed-off-by: Koichiro Den <koichiro.den@canonical.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/all/20241220134421.3809834-1-koichiro.den@canonical.com
The group's ignore flag is:
_ read under the group's lock (idle entry, remote expiry)
_ turned on/off under the group's lock (idle entry, remote expiry)
_ turned on locklessly on idle exit
When idle entry or remote expiry clear the "ignore" flag of a group, the
operation must be synchronized against other concurrent idle entry or
remote expiry to make sure the related group timer is never missed. To
enforce this synchronization, both "ignore" clear and read are
performed under the group lock.
On the contrary, whether idle entry or remote expiry manage to observe
the "ignore" flag turned on by a CPU exiting idle is a matter of
optimization. If that flag set is missed or cleared concurrently, the
worst outcome is a migrator wasting time remotely handling a "ghost"
timer. This is why the ignore flag can be set locklessly.
Unfortunately, the related lockless accesses are bare and miss
appropriate annotations. KCSAN rightfully complains:
BUG: KCSAN: data-race in __tmigr_cpu_activate / print_report
write to 0xffff88842fc28004 of 1 bytes by task 0 on cpu 0:
__tmigr_cpu_activate
tmigr_cpu_activate
timer_clear_idle
tick_nohz_restart_sched_tick
tick_nohz_idle_exit
do_idle
cpu_startup_entry
kernel_init
do_initcalls
clear_bss
reserve_bios_regions
common_startup_64
read to 0xffff88842fc28004 of 1 bytes by task 0 on cpu 1:
print_report
kcsan_report_known_origin
kcsan_setup_watchpoint
tmigr_next_groupevt
tmigr_update_events
tmigr_inactive_up
__walk_groups+0x50/0x77
walk_groups
__tmigr_cpu_deactivate
tmigr_cpu_deactivate
__get_next_timer_interrupt
timer_base_try_to_set_idle
tick_nohz_stop_tick
tick_nohz_idle_stop_tick
cpuidle_idle_call
do_idle
Although the relevant accesses could be marked as data_race(), the
"ignore" flag being read several times within the same
tmigr_update_events() function is confusing and error prone. Prefer
reading it once in that function and make use of similar/paired accesses
elsewhere with appropriate comments when necessary.
Reported-by: kernel test robot <oliver.sang@intel.com>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/20250114231507.21672-4-frederic@kernel.org
Closes: https://lore.kernel.org/oe-lkp/202501031612.62e0c498-lkp@intel.com
Commit 2522c84db513 ("timers/migration: Fix another race between hotplug
and idle entry/exit") fixed yet another race between idle exit and CPU
hotplug up leading to a wrong "0" value migrator assigned to the top
level. However there is yet another situation that remains unhandled:
[GRP0:0]
migrator = TMIGR_NONE
active = NONE
groupmask = 1
/ \ \
0 1 2..7
idle idle idle
0) The system is fully idle.
[GRP0:0]
migrator = CPU 0
active = CPU 0
groupmask = 1
/ \ \
0 1 2..7
active idle idle
1) CPU 0 is activating. It has done the cmpxchg on the top's ->migr_state
but it hasn't yet returned to __walk_groups().
[GRP0:0]
migrator = CPU 0
active = CPU 0, CPU 1
groupmask = 1
/ \ \
0 1 2..7
active active idle
2) CPU 1 is activating. CPU 0 stays the migrator (still stuck in
__walk_groups(), delayed by #VMEXIT for example).
[GRP1:0]
migrator = TMIGR_NONE
active = NONE
groupmask = 1
/ \
[GRP0:0] [GRP0:1]
migrator = CPU 0 migrator = TMIGR_NONE
active = CPU 0, CPU1 active = NONE
groupmask = 1 groupmask = 2
/ \ \
0 1 2..7 8
active active idle !online
3) CPU 8 is preparing to boot. CPUHP_TMIGR_PREPARE is being ran by CPU 1
which has created the GRP0:1 and the new top GRP1:0 connected to GRP0:1
and GRP0:0. CPU 1 hasn't yet propagated its activation up to GRP1:0.
[GRP1:0]
migrator = GRP0:0
active = GRP0:0
groupmask = 1
/ \
[GRP0:0] [GRP0:1]
migrator = CPU 0 migrator = TMIGR_NONE
active = CPU 0, CPU1 active = NONE
groupmask = 1 groupmask = 2
/ \ \
0 1 2..7 8
active active idle !online
4) CPU 0 finally resumed after its #VMEXIT. It's in __walk_groups()
returning from tmigr_cpu_active(). The new top GRP1:0 is visible and
fetched and the pre-initialized groupmask of GRP0:0 is also visible.
As a result tmigr_active_up() is called to GRP1:0 with GRP0:0 as active
and migrator. CPU 0 is returning to __walk_groups() but suffers again
a #VMEXIT.
[GRP1:0]
migrator = GRP0:0
active = GRP0:0
groupmask = 1
/ \
[GRP0:0] [GRP0:1]
migrator = CPU 0 migrator = TMIGR_NONE
active = CPU 0, CPU1 active = NONE
groupmask = 1 groupmask = 2
/ \ \
0 1 2..7 8
active active idle !online
5) CPU 1 propagates its activation of GRP0:0 to GRP1:0. This has no
effect since CPU 0 did it already.
[GRP1:0]
migrator = GRP0:0
active = GRP0:0, GRP0:1
groupmask = 1
/ \
[GRP0:0] [GRP0:1]
migrator = CPU 0 migrator = CPU 8
active = CPU 0, CPU1 active = CPU 8
groupmask = 1 groupmask = 2
/ \ \ \
0 1 2..7 8
active active idle active
6) CPU 1 links CPU 8 to its group. CPU 8 boots and goes through
CPUHP_AP_TMIGR_ONLINE which propagates activation.
[GRP2:0]
migrator = TMIGR_NONE
active = NONE
groupmask = 1
/ \
[GRP1:0] [GRP1:1]
migrator = GRP0:0 migrator = TMIGR_NONE
active = GRP0:0, GRP0:1 active = NONE
groupmask = 1 groupmask = 2
/ \
[GRP0:0] [GRP0:1] [GRP0:2]
migrator = CPU 0 migrator = CPU 8 migrator = TMIGR_NONE
active = CPU 0, CPU1 active = CPU 8 active = NONE
groupmask = 1 groupmask = 2 groupmask = 0
/ \ \ \
0 1 2..7 8 64
active active idle active !online
7) CPU 64 is booting. CPUHP_TMIGR_PREPARE is being ran by CPU 1
which has created the GRP1:1, GRP0:2 and the new top GRP2:0 connected to
GRP1:1 and GRP1:0. CPU 1 hasn't yet propagated its activation up to
GRP2:0.
[GRP2:0]
migrator = 0 (!!!)
active = NONE
groupmask = 1
/ \
[GRP1:0] [GRP1:1]
migrator = GRP0:0 migrator = TMIGR_NONE
active = GRP0:0, GRP0:1 active = NONE
groupmask = 1 groupmask = 2
/ \
[GRP0:0] [GRP0:1] [GRP0:2]
migrator = CPU 0 migrator = CPU 8 migrator = TMIGR_NONE
active = CPU 0, CPU1 active = CPU 8 active = NONE
groupmask = 1 groupmask = 2 groupmask = 0
/ \ \ \
0 1 2..7 8 64
active active idle active !online
8) CPU 0 finally resumed after its #VMEXIT. It's in __walk_groups()
returning from tmigr_cpu_active(). The new top GRP2:0 is visible and
fetched but the pre-initialized groupmask of GRP1:0 is not because no
ordering made its initialization visible. As a result tmigr_active_up()
may be called to GRP2:0 with a "0" child's groumask. Leaving the timers
ignored for ever when the system is fully idle.
The race is highly theoretical and perhaps impossible in practice but
the groupmask of the child is not the only concern here as the whole
initialization of the child is not guaranteed to be visible to any
tree walker racing against hotplug (idle entry/exit, remote handling,
etc...). Although the current code layout seem to be resilient to such
hazards, this doesn't tell much about the future.
Fix this with enforcing address dependency between group initialization
and the write/read to the group's parent's pointer. Fortunately that
doesn't involve any barrier addition in the fast paths.
Fixes: 10a0e6f3d3 ("timers/migration: Move hierarchy setup into cpuhotplug prepare callback")
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/all/20250114231507.21672-3-frederic@kernel.org
Commit 10a0e6f3d3 ("timers/migration: Move hierarchy setup into
cpuhotplug prepare callback") fixed a race between idle exit and CPU
hotplug up leading to a wrong "0" value migrator assigned to the top
level. However there is still a situation that remains unhandled:
[GRP0:0]
migrator = TMIGR_NONE
active = NONE
groupmask = 0
/ \ \
0 1 2..7
idle idle idle
0) The system is fully idle.
[GRP0:0]
migrator = CPU 0
active = CPU 0
groupmask = 0
/ \ \
0 1 2..7
active idle idle
1) CPU 0 is activating. It has done the cmpxchg on the top's ->migr_state
but it hasn't yet returned to __walk_groups().
[GRP0:0]
migrator = CPU 0
active = CPU 0, CPU 1
groupmask = 0
/ \ \
0 1 2..7
active active idle
2) CPU 1 is activating. CPU 0 stays the migrator (still stuck in
__walk_groups(), delayed by #VMEXIT for example).
[GRP1:0]
migrator = TMIGR_NONE
active = NONE
groupmask = 0
/ \
[GRP0:0] [GRP0:1]
migrator = CPU 0 migrator = TMIGR_NONE
active = CPU 0, CPU1 active = NONE
groupmask = 2 groupmask = 1
/ \ \
0 1 2..7 8
active active idle !online
3) CPU 8 is preparing to boot. CPUHP_TMIGR_PREPARE is being ran by CPU 1
which has created the GRP0:1 and the new top GRP1:0 connected to GRP0:1
and GRP0:0. The groupmask of GRP0:0 is now 2. CPU 1 hasn't yet
propagated its activation up to GRP1:0.
[GRP1:0]
migrator = 0 (!!!)
active = NONE
groupmask = 0
/ \
[GRP0:0] [GRP0:1]
migrator = CPU 0 migrator = TMIGR_NONE
active = CPU 0, CPU1 active = NONE
groupmask = 2 groupmask = 1
/ \ \
0 1 2..7 8
active active idle !online
4) CPU 0 finally resumed after its #VMEXIT. It's in __walk_groups()
returning from tmigr_cpu_active(). The new top GRP1:0 is visible and
fetched but the freshly updated groupmask of GRP0:0 may not be visible
due to lack of ordering! As a result tmigr_active_up() is called to
GRP0:0 with a child's groupmask of "0". This buggy "0" groupmask then
becomes the migrator for GRP1:0 forever. As a result, timers on a fully
idle system get ignored.
One possible fix would be to define TMIGR_NONE as "0" so that such a
race would have no effect. And after all TMIGR_NONE doesn't need to be
anything else. However this would leave an uncomfortable state machine
where gears happen not to break by chance but are vulnerable to future
modifications.
Keep TMIGR_NONE as is instead and pre-initialize to "1" the groupmask of
any newly created top level. This groupmask is guaranteed to be visible
upon fetching the corresponding group for the 1st time:
_ By the upcoming CPU thanks to CPU hotplug synchronization between the
control CPU (BP) and the booting one (AP).
_ By the control CPU since the groupmask and parent pointers are
initialized locally.
_ By all CPUs belonging to the same group than the control CPU because
they must wait for it to ever become idle before needing to walk to
the new top. The cmpcxhg() on ->migr_state then makes sure its
groupmask is visible.
With this pre-initialization, it is guaranteed that if a future top level
is linked to an old one, it is walked through with a valid groupmask.
Fixes: 10a0e6f3d3 ("timers/migration: Move hierarchy setup into cpuhotplug prepare callback")
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/all/20250114231507.21672-2-frederic@kernel.org
If a timer is deferrable and NO_HZ_COMMON is enabled, get_timer_cpu_base()
and get_timer_this_cpu_base() invoke per_cpu_ptr() and this_cpu_ptr()
twice.
While this seems to be cheap, get_timer_cpu_base() can be called in a loop
in lock_timer_base().
Optimize the functions by updating the base index for deferrable timers and
retrieving the actual base pointer once.
In both cases the resulting assembly code of those helpers becomes smaller,
which results in a ~30% execution time reduction for a lock_timer_base()
micro bench mark.
Signed-off-by: Zhongqiu Han <quic_zhonhan@quicinc.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Link: https://lore.kernel.org/all/20241231150115.1978342-1-quic_zhonhan@quicinc.com
ktime_get_fast_timestamps() was added in 2020 by commit e2d977c9f1
("timekeeping: Provide multi-timestamp accessor to NMI safe timekeeper")
but has remained unused.
Remove it.
[ tglx: Fold the inline as David suggested in the submission ]
Signed-off-by: Dr. David Alan Gilbert <linux@treblig.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/20250112160132.450209-1-linux@treblig.org
Use the correct kernel-doc notation for nested structs/unions to
eliminate warnings:
timer_migration.h:119: warning: Incorrect use of kernel-doc format: * struct - split state of tmigr_group
timer_migration.h:134: warning: Function parameter or struct member 'active' not described in 'tmigr_state'
timer_migration.h:134: warning: Function parameter or struct member 'migrator' not described in 'tmigr_state'
timer_migration.h:134: warning: Function parameter or struct member 'seq' not described in 'tmigr_state'
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/20250111063156.910903-1-rdunlap@infradead.org
Add kernel-doc comments for two parameters to eliminate kernel-doc warnings:
tick-broadcast.c:1026: warning: Function parameter or struct member 'bc' not described in 'tick_broadcast_setup_oneshot'
tick-broadcast.c:1026: warning: Function parameter or struct member 'from_periodic' not described in 'tick_broadcast_setup_oneshot'
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/20250111063148.910887-1-rdunlap@infradead.org
The return type should be 'bool' instead of 'int' according to the calling
context in the kernel, and its internal implementation, i.e. :
return timerqueue_add();
which is a bool-return function.
[ tglx: Adjust function arguments ]
Signed-off-by: Richard Clark <richard.xnu.clark@gmail.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/Z2ppT7me13dtxm1a@MBC02GN1V4Q05P
When a pair of clocksource reads separated by a udelay(1) claim less than a
full microsecond of elapsed time, print the measured delay as part of the
splat.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/717a2ddf-a80f-490b-aa3a-4e4b74fa56ca@paulmck-laptop
Guenter reported boot stalls on a emulated ARM 32-bit platform, which has a
24-bit wide clocksource.
It turns out that the calculated maximal idle time, which limits idle
sleeps to prevent clocksource wrap arounds, is close to the point where the
negative motion detection triggers.
max_idle_ns: 597268854 ns
negative motion tripping point: 671088640 ns
If the idle wakeup is delayed beyond that point, the clocksource
advances far enough to trigger the negative motion detection. This
prevents the clock to advance and in the worst case the system stalls
completely if the consecutive sleeps based on the stale clock are
delayed as well.
Cure this by calculating a more robust cut-off value for negative motion,
which covers 87.5% of the actual clocksource counter width. Compare the
delta against this value to catch negative motion. This is specifically for
clock sources with a small counter width as their wrap around time is close
to the half counter width. For clock sources with wide counters this is not
a problem because the maximum idle time is far from the half counter width
due to the math overflow protection constraints.
For the case at hand this results in a tripping point of 1174405120ns.
Note, that this cannot prevent issues when the delay exceeds the 87.5%
margin, but that's not different from the previous unchecked version which
allowed arbitrary time jumps.
Systems with small counter width are prone to invalid results, but this
problem is unlikely to be seen on real hardware. If such a system
completely stalls for more than half a second, then there are other more
urgent problems than the counter wrapping around.
Fixes: c163e40af9 ("timekeeping: Always check for negative motion")
Reported-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Guenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/all/8734j5ul4x.ffs@tglx
Closes: https://lore.kernel.org/all/387b120b-d68a-45e8-b6ab-768cd95d11c2@roeck-us.net
Due to an unsigned cast, adjtimex() returns the wrong offest when using
ADJ_MICRO and the offset is negative. In this case a small negative offset
returns approximately 4.29 seconds (~ 2^32/1000 milliseconds) due to the
unsigned cast of the negative offset.
This cast was added when the kernel internal struct timex was changed to
use type long long for the time offset value to address the problem of a
64bit/32bit division on 32bit systems.
The correct cast would have been (s32), which is correct as time_offset can
only be in the range of [INT_MIN..INT_MAX] because the shift constant used
for calculating it is 32. But that's non-obvious.
Remove the cast and use div_s64() to cure the issue.
[ tglx: Fix white space damage, use div_s64() and amend the change log ]
Fixes: ead25417f8 ("timex: use __kernel_timex internally")
Signed-off-by: Marcelo Dalmas <marcelo.dalmas@ge.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/all/SJ0P101MB03687BF7D5A10FD3C49C51E5F42E2@SJ0P101MB0368.NAMP101.PROD.OUTLOOK.COM
- The final step to get rid of auto-rearming posix-timers
posix-timers are currently auto-rearmed by the kernel when the signal
of the timer is ignored so that the timer signal can be delivered once
the corresponding signal is unignored.
This requires to throttle the timer to prevent a DoS by small intervals
and keeps the system pointlessly out of low power states for no value.
This is a long standing non-trivial problem due to the lock order of
posix-timer lock and the sighand lock along with life time issues as
the timer and the sigqueue have different life time rules.
Cure this by:
* Embedding the sigqueue into the timer struct to have the same life
time rules. Aside of that this also avoids the lookup of the timer
in the signal delivery and rearm path as it's just a always valid
container_of() now.
* Queuing ignored timer signals onto a seperate ignored list.
* Moving queued timer signals onto the ignored list when the signal is
switched to SIG_IGN before it could be delivered.
* Walking the ignored list when SIG_IGN is lifted and requeue the
signals to the actual signal lists. This allows the signal delivery
code to rearm the timer.
This also required to consolidate the signal delivery rules so they are
consistent across all situations. With that all self test scenarios
finally succeed.
- Core infrastructure for VFS multigrain timestamping
This is required to allow the kernel to use coarse grained time stamps
by default and switch to fine grained time stamps when inode attributes
are actively observed via getattr().
These changes have been provided to the VFS tree as well, so that the
VFS specific infrastructure could be built on top.
- Cleanup and consolidation of the sleep() infrastructure
* Move all sleep and timeout functions into one file
* Rework udelay() and ndelay() into proper documented inline functions
and replace the hardcoded magic numbers by proper defines.
* Rework the fsleep() implementation to take the reality of the timer
wheel granularity on different HZ values into account. Right now the
boundaries are hard coded time ranges which fail to provide the
requested accuracy on different HZ settings.
* Update documentation for all sleep/timeout related functions and fix
up stale documentation links all over the place
* Fixup a few usage sites
- Rework of timekeeping and adjtimex(2) to prepare for multiple PTP clocks
A system can have multiple PTP clocks which are participating in
seperate and independent PTP clock domains. So far the kernel only
considers the PTP clock which is based on CLOCK TAI relevant as that's
the clock which drives the timekeeping adjustments via the various user
space daemons through adjtimex(2).
The non TAI based clock domains are accessible via the file descriptor
based posix clocks, but their usability is very limited. They can't be
accessed fast as they always go all the way out to the hardware and
they cannot be utilized in the kernel itself.
As Time Sensitive Networking (TSN) gains traction it is required to
provide fast user and kernel space access to these clocks.
The approach taken is to utilize the timekeeping and adjtimex(2)
infrastructure to provide this access in a similar way how the kernel
provides access to clock MONOTONIC, REALTIME etc.
Instead of creating a duplicated infrastructure this rework converts
timekeeping and adjtimex(2) into generic functionality which operates
on pointers to data structures instead of using static variables.
This allows to provide time accessors and adjtimex(2) functionality for
the independent PTP clocks in a subsequent step.
- Consolidate hrtimer initialization
hrtimers are set up by initializing the data structure and then
seperately setting the callback function for historical reasons.
That's an extra unnecessary step and makes Rust support less straight
forward than it should be.
Provide a new set of hrtimer_setup*() functions and convert the core
code and a few usage sites of the less frequently used interfaces over.
The bulk of the htimer_init() to hrtimer_setup() conversion is already
prepared and scheduled for the next merge window.
- Drivers:
* Ensure that the global timekeeping clocksource is utilizing the
cluster 0 timer on MIPS multi-cluster systems.
Otherwise CPUs on different clusters use their cluster specific
clocksource which is not guaranteed to be synchronized with other
clusters.
* Mostly boring cleanups, fixes, improvements and code movement
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Merge tag 'timers-core-2024-11-18' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull timer updates from Thomas Gleixner:
"A rather large update for timekeeping and timers:
- The final step to get rid of auto-rearming posix-timers
posix-timers are currently auto-rearmed by the kernel when the
signal of the timer is ignored so that the timer signal can be
delivered once the corresponding signal is unignored.
This requires to throttle the timer to prevent a DoS by small
intervals and keeps the system pointlessly out of low power states
for no value. This is a long standing non-trivial problem due to
the lock order of posix-timer lock and the sighand lock along with
life time issues as the timer and the sigqueue have different life
time rules.
Cure this by:
- Embedding the sigqueue into the timer struct to have the same
life time rules. Aside of that this also avoids the lookup of
the timer in the signal delivery and rearm path as it's just a
always valid container_of() now.
- Queuing ignored timer signals onto a seperate ignored list.
- Moving queued timer signals onto the ignored list when the
signal is switched to SIG_IGN before it could be delivered.
- Walking the ignored list when SIG_IGN is lifted and requeue the
signals to the actual signal lists. This allows the signal
delivery code to rearm the timer.
This also required to consolidate the signal delivery rules so they
are consistent across all situations. With that all self test
scenarios finally succeed.
- Core infrastructure for VFS multigrain timestamping
This is required to allow the kernel to use coarse grained time
stamps by default and switch to fine grained time stamps when inode
attributes are actively observed via getattr().
These changes have been provided to the VFS tree as well, so that
the VFS specific infrastructure could be built on top.
- Cleanup and consolidation of the sleep() infrastructure
- Move all sleep and timeout functions into one file
- Rework udelay() and ndelay() into proper documented inline
functions and replace the hardcoded magic numbers by proper
defines.
- Rework the fsleep() implementation to take the reality of the
timer wheel granularity on different HZ values into account.
Right now the boundaries are hard coded time ranges which fail
to provide the requested accuracy on different HZ settings.
- Update documentation for all sleep/timeout related functions
and fix up stale documentation links all over the place
- Fixup a few usage sites
- Rework of timekeeping and adjtimex(2) to prepare for multiple PTP
clocks
A system can have multiple PTP clocks which are participating in
seperate and independent PTP clock domains. So far the kernel only
considers the PTP clock which is based on CLOCK TAI relevant as
that's the clock which drives the timekeeping adjustments via the
various user space daemons through adjtimex(2).
The non TAI based clock domains are accessible via the file
descriptor based posix clocks, but their usability is very limited.
They can't be accessed fast as they always go all the way out to
the hardware and they cannot be utilized in the kernel itself.
As Time Sensitive Networking (TSN) gains traction it is required to
provide fast user and kernel space access to these clocks.
The approach taken is to utilize the timekeeping and adjtimex(2)
infrastructure to provide this access in a similar way how the
kernel provides access to clock MONOTONIC, REALTIME etc.
Instead of creating a duplicated infrastructure this rework
converts timekeeping and adjtimex(2) into generic functionality
which operates on pointers to data structures instead of using
static variables.
This allows to provide time accessors and adjtimex(2) functionality
for the independent PTP clocks in a subsequent step.
- Consolidate hrtimer initialization
hrtimers are set up by initializing the data structure and then
seperately setting the callback function for historical reasons.
That's an extra unnecessary step and makes Rust support less
straight forward than it should be.
Provide a new set of hrtimer_setup*() functions and convert the
core code and a few usage sites of the less frequently used
interfaces over.
The bulk of the htimer_init() to hrtimer_setup() conversion is
already prepared and scheduled for the next merge window.
- Drivers:
- Ensure that the global timekeeping clocksource is utilizing the
cluster 0 timer on MIPS multi-cluster systems.
Otherwise CPUs on different clusters use their cluster specific
clocksource which is not guaranteed to be synchronized with
other clusters.
- Mostly boring cleanups, fixes, improvements and code movement"
* tag 'timers-core-2024-11-18' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (140 commits)
posix-timers: Fix spurious warning on double enqueue versus do_exit()
clocksource/drivers/arm_arch_timer: Use of_property_present() for non-boolean properties
clocksource/drivers/gpx: Remove redundant casts
clocksource/drivers/timer-ti-dm: Fix child node refcount handling
dt-bindings: timer: actions,owl-timer: convert to YAML
clocksource/drivers/ralink: Add Ralink System Tick Counter driver
clocksource/drivers/mips-gic-timer: Always use cluster 0 counter as clocksource
clocksource/drivers/timer-ti-dm: Don't fail probe if int not found
clocksource/drivers:sp804: Make user selectable
clocksource/drivers/dw_apb: Remove unused dw_apb_clockevent functions
hrtimers: Delete hrtimer_init_on_stack()
alarmtimer: Switch to use hrtimer_setup() and hrtimer_setup_on_stack()
io_uring: Switch to use hrtimer_setup_on_stack()
sched/idle: Switch to use hrtimer_setup_on_stack()
hrtimers: Delete hrtimer_init_sleeper_on_stack()
wait: Switch to use hrtimer_setup_sleeper_on_stack()
timers: Switch to use hrtimer_setup_sleeper_on_stack()
net: pktgen: Switch to use hrtimer_setup_sleeper_on_stack()
futex: Switch to use hrtimer_setup_sleeper_on_stack()
fs/aio: Switch to use hrtimer_setup_sleeper_on_stack()
...
The VDSO data page handling is architecture specific for historical
reasons, but there is no real technical reason to do so.
Aside of that VDSO data has become a dump ground for various mechanisms
and fail to provide a clear separation of the functionalities.
Clean this up by:
* consolidating the VDSO page data by getting rid of architecture
specific warts especially in x86 and PowerPC.
* removing the last includes of header files which are pulling in other
headers outside of the VDSO namespace.
* seperating timekeeping and other VDSO data accordingly.
Further consolidation of the VDSO page handling is done in subsequent
changes scheduled for the next merge window.
This also lays the ground for expanding the VDSO time getters for
independent PTP clocks in a generic way without making every architecture
add support seperately.
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Merge tag 'timers-vdso-2024-11-18' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull vdso data page handling updates from Thomas Gleixner:
"First steps of consolidating the VDSO data page handling.
The VDSO data page handling is architecture specific for historical
reasons, but there is no real technical reason to do so.
Aside of that VDSO data has become a dump ground for various
mechanisms and fail to provide a clear separation of the
functionalities.
Clean this up by:
- consolidating the VDSO page data by getting rid of architecture
specific warts especially in x86 and PowerPC.
- removing the last includes of header files which are pulling in
other headers outside of the VDSO namespace.
- seperating timekeeping and other VDSO data accordingly.
Further consolidation of the VDSO page handling is done in subsequent
changes scheduled for the next merge window.
This also lays the ground for expanding the VDSO time getters for
independent PTP clocks in a generic way without making every
architecture add support seperately"
* tag 'timers-vdso-2024-11-18' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (42 commits)
x86/vdso: Add missing brackets in switch case
vdso: Rename struct arch_vdso_data to arch_vdso_time_data
powerpc: Split systemcfg struct definitions out from vdso
powerpc: Split systemcfg data out of vdso data page
powerpc: Add kconfig option for the systemcfg page
powerpc/pseries/lparcfg: Use num_possible_cpus() for potential processors
powerpc/pseries/lparcfg: Fix printing of system_active_processors
powerpc/procfs: Propagate error of remap_pfn_range()
powerpc/vdso: Remove offset comment from 32bit vdso_arch_data
x86/vdso: Split virtual clock pages into dedicated mapping
x86/vdso: Delete vvar.h
x86/vdso: Access vdso data without vvar.h
x86/vdso: Move the rng offset to vsyscall.h
x86/vdso: Access rng vdso data without vvar.h
x86/vdso: Access timens vdso data without vvar.h
x86/vdso: Allocate vvar page from C code
x86/vdso: Access rng data from kernel without vvar
x86/vdso: Place vdso_data at beginning of vvar page
x86/vdso: Use __arch_get_vdso_data() to access vdso data
x86/mm/mmap: Remove arch_vma_name()
...
- Tree wide:
* Make nr_irqs static to the core code and provide accessor functions
to remove existing and prevent future aliasing problems with local
variables or function arguments of the same name.
- Core code:
* Prevent freeing an interrupt in the devres code which is not managed
by devres in the first place.
* Use seq_put_decimal_ull_width() for decimal values output in
/proc/interrupts which increases performance significantly as it
avoids parsing the format strings over and over.
* Optimize raising the timer and hrtimer soft interrupts by using the
'set bit only' variants instead of the combined version which checks
whether ksoftirqd should be woken up. The latter is a pointless
exercise as both soft interrupts are raised in the context of the
timer interrupt and therefore never wake up ksoftirqd.
* Delegate timer/hrtimer soft interrupt processing to a dedicated thread
on RT.
Timer and hrtimer soft interrupts are always processed in ksoftirqd
on RT enabled kernels. This can lead to high latencies when other
soft interrupts are delegated to ksoftirqd as well.
The separate thread allows to run them seperately under a RT
scheduling policy to reduce the latency overhead.
- Drivers:
* New drivers or extensions of existing drivers to support Renesas
RZ/V2H(P), Aspeed AST27XX, T-HEAD C900 and ATMEL sam9x7 interrupt
chips
* Support for multi-cluster GICs on MIPS.
MIPS CPUs can come with multiple CPU clusters, where each CPU cluster
has its own GIC (Generic Interrupt Controller). This requires to
access the GIC of a remote cluster through a redirect register block.
This is encapsulated into a set of helper functions to keep the
complexity out of the actual code paths which handle the GIC details.
* Support for encrypted guests in the ARM GICV3 ITS driver
The ITS page needs to be shared with the hypervisor and therefore
must be decrypted.
* Small cleanups and fixes all over the place
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Merge tag 'irq-core-2024-11-18' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull interrupt subsystem updates from Thomas Gleixner:
"Tree wide:
- Make nr_irqs static to the core code and provide accessor functions
to remove existing and prevent future aliasing problems with local
variables or function arguments of the same name.
Core code:
- Prevent freeing an interrupt in the devres code which is not
managed by devres in the first place.
- Use seq_put_decimal_ull_width() for decimal values output in
/proc/interrupts which increases performance significantly as it
avoids parsing the format strings over and over.
- Optimize raising the timer and hrtimer soft interrupts by using the
'set bit only' variants instead of the combined version which
checks whether ksoftirqd should be woken up. The latter is a
pointless exercise as both soft interrupts are raised in the
context of the timer interrupt and therefore never wake up
ksoftirqd.
- Delegate timer/hrtimer soft interrupt processing to a dedicated
thread on RT.
Timer and hrtimer soft interrupts are always processed in ksoftirqd
on RT enabled kernels. This can lead to high latencies when other
soft interrupts are delegated to ksoftirqd as well.
The separate thread allows to run them seperately under a RT
scheduling policy to reduce the latency overhead.
Drivers:
- New drivers or extensions of existing drivers to support Renesas
RZ/V2H(P), Aspeed AST27XX, T-HEAD C900 and ATMEL sam9x7 interrupt
chips
- Support for multi-cluster GICs on MIPS.
MIPS CPUs can come with multiple CPU clusters, where each CPU
cluster has its own GIC (Generic Interrupt Controller). This
requires to access the GIC of a remote cluster through a redirect
register block.
This is encapsulated into a set of helper functions to keep the
complexity out of the actual code paths which handle the GIC
details.
- Support for encrypted guests in the ARM GICV3 ITS driver
The ITS page needs to be shared with the hypervisor and therefore
must be decrypted.
- Small cleanups and fixes all over the place"
* tag 'irq-core-2024-11-18' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (50 commits)
irqchip/riscv-aplic: Prevent crash when MSI domain is missing
genirq/proc: Use seq_put_decimal_ull_width() for decimal values
softirq: Use a dedicated thread for timer wakeups on PREEMPT_RT.
timers: Use __raise_softirq_irqoff() to raise the softirq.
hrtimer: Use __raise_softirq_irqoff() to raise the softirq
riscv: defconfig: Enable T-HEAD C900 ACLINT SSWI drivers
irqchip: Add T-HEAD C900 ACLINT SSWI driver
dt-bindings: interrupt-controller: Add T-HEAD C900 ACLINT SSWI device
irqchip/stm32mp-exti: Use of_property_present() for non-boolean properties
irqchip/mips-gic: Fix selection of GENERIC_IRQ_EFFECTIVE_AFF_MASK
irqchip/mips-gic: Prevent indirect access to clusters without CPU cores
irqchip/mips-gic: Multi-cluster support
irqchip/mips-gic: Setup defaults in each cluster
irqchip/mips-gic: Support multi-cluster in for_each_online_cpu_gic()
irqchip/mips-gic: Replace open coded online CPU iterations
genirq/irqdesc: Use str_enabled_disabled() helper in wakeup_show()
genirq/devres: Don't free interrupt which is not managed by devres
irqchip/gic-v3-its: Fix over allocation in itt_alloc_pool()
irqchip/aspeed-intc: Add AST27XX INTC support
dt-bindings: interrupt-controller: Add support for ASPEED AST27XX INTC
...
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Merge tag 'vfs-6.13.mgtime' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs
Pull vfs multigrain timestamps from Christian Brauner:
"This is another try at implementing multigrain timestamps. This time
with significant help from the timekeeping maintainers to reduce the
performance impact.
Thomas provided a base branch that contains the required timekeeping
interfaces for the VFS. It serves as the base for the multi-grain
timestamp work:
- Multigrain timestamps allow the kernel to use fine-grained
timestamps when an inode's attributes is being actively observed
via ->getattr(). With this support, it's possible for a file to get
a fine-grained timestamp, and another modified after it to get a
coarse-grained stamp that is earlier than the fine-grained time. If
this happens then the files can appear to have been modified in
reverse order, which breaks VFS ordering guarantees.
To prevent this, a floor value is maintained for multigrain
timestamps. Whenever a fine-grained timestamp is handed out, record
it, and when later coarse-grained stamps are handed out, ensure
they are not earlier than that value. If the coarse-grained
timestamp is earlier than the fine-grained floor, return the floor
value instead.
The timekeeper changes add a static singleton atomic64_t into
timekeeper.c that is used to keep track of the latest fine-grained
time ever handed out. This is tracked as a monotonic ktime_t value
to ensure that it isn't affected by clock jumps. Because it is
updated at different times than the rest of the timekeeper object,
the floor value is managed independently of the timekeeper via a
cmpxchg() operation, and sits on its own cacheline.
Two new public timekeeper interfaces are added:
(1) ktime_get_coarse_real_ts64_mg() fills a timespec64 with the
later of the coarse-grained clock and the floor time
(2) ktime_get_real_ts64_mg() gets the fine-grained clock value,
and tries to swap it into the floor. A timespec64 is filled
with the result.
- The VFS has always used coarse-grained timestamps when updating the
ctime and mtime after a change. This has the benefit of allowing
filesystems to optimize away a lot metadata updates, down to around
1 per jiffy, even when a file is under heavy writes.
Unfortunately, this has always been an issue when we're exporting
via NFSv3, which relies on timestamps to validate caches. A lot of
changes can happen in a jiffy, so timestamps aren't sufficient to
help the client decide when to invalidate the cache. Even with
NFSv4, a lot of exported filesystems don't properly support a
change attribute and are subject to the same problems with
timestamp granularity. Other applications have similar issues with
timestamps (e.g backup applications).
If we were to always use fine-grained timestamps, that would
improve the situation, but that becomes rather expensive, as the
underlying filesystem would have to log a lot more metadata
updates.
This adds a way to only use fine-grained timestamps when they are
being actively queried. Use the (unused) top bit in
inode->i_ctime_nsec as a flag that indicates whether the current
timestamps have been queried via stat() or the like. When it's set,
we allow the kernel to use a fine-grained timestamp iff it's
necessary to make the ctime show a different value.
This solves the problem of being able to distinguish the timestamp
between updates, but introduces a new problem: it's now possible
for a file being changed to get a fine-grained timestamp. A file
that is altered just a bit later can then get a coarse-grained one
that appears older than the earlier fine-grained time. This
violates timestamp ordering guarantees.
This is where the earlier mentioned timkeeping interfaces help. A
global monotonic atomic64_t value is kept that acts as a timestamp
floor. When we go to stamp a file, we first get the latter of the
current floor value and the current coarse-grained time. If the
inode ctime hasn't been queried then we just attempt to stamp it
with that value.
If it has been queried, then first see whether the current coarse
time is later than the existing ctime. If it is, then we accept
that value. If it isn't, then we get a fine-grained time and try to
swap that into the global floor. Whether that succeeds or fails, we
take the resulting floor time, convert it to realtime and try to
swap that into the ctime.
We take the result of the ctime swap whether it succeeds or fails,
since either is just as valid.
Filesystems can opt into this by setting the FS_MGTIME fstype flag.
Others should be unaffected (other than being subject to the same
floor value as multigrain filesystems)"
* tag 'vfs-6.13.mgtime' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs:
fs: reduce pointer chasing in is_mgtime() test
tmpfs: add support for multigrain timestamps
btrfs: convert to multigrain timestamps
ext4: switch to multigrain timestamps
xfs: switch to multigrain timestamps
Documentation: add a new file documenting multigrain timestamps
fs: add percpu counters for significant multigrain timestamp events
fs: tracepoints around multigrain timestamp events
fs: handle delegated timestamps in setattr_copy_mgtime
timekeeping: Add percpu counter for tracking floor swap events
timekeeping: Add interfaces for handling timestamps with a floor value
fs: have setattr_copy handle multigrain timestamps appropriately
fs: add infrastructure for multigrain timestamps
hrtimer_setup() and hrtimer_setup_on_stack() take the callback function
pointer as argument and initialize the timer completely.
Replace the hrtimer_init*() variants and the open coded initialization of
hrtimer::function with the new setup mechanism.
Switch to use the new functions.
Signed-off-by: Nam Cao <namcao@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/2bae912336103405adcdab96b88d3ea0353b4228.1730386209.git.namcao@linutronix.de
The hrtimer_init*() API is replaced by hrtimer_setup*() variants to
initialize the timer including the callback function at once.
hrtimer_init_sleeper_on_stack() does not need user to setup the callback
function separately, so a new variant would not be strictly necessary.
Nonetheless, to keep the naming convention consistent, introduce
hrtimer_setup_sleeper_on_stack(). hrtimer_init_on_stack() will be removed
once all users are converted.
Signed-off-by: Nam Cao <namcao@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/7b5e18e6dd0ace9eaa211201528cb9dc23752454.1730386209.git.namcao@linutronix.de
To initialize hrtimer on stack, hrtimer_init_on_stack() needs to be called
and also hrtimer::function must be set. This is error-prone and awkward to
use.
Introduce hrtimer_setup_on_stack() which does both of these things, so that
users of hrtimer can be simplified.
The new setup function also has a sanity check for the provided function
pointer. If NULL, a warning is emitted and a dummy callback installed.
hrtimer_init_on_stack() will be removed as soon as all of its users have
been converted to the new function.
Signed-off-by: Nam Cao <namcao@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/4b05e2ab3a82c517adf67fabc0f0cd8fe118b97c.1730386209.git.namcao@linutronix.de
To initialize hrtimer, hrtimer_init() needs to be called and also
hrtimer::function must be set. This is error-prone and awkward to use.
Introduce hrtimer_setup() which does both of these things, so that users of
hrtimer can be simplified.
The new setup function also has a sanity check for the provided function
pointer. If NULL, a warning is emitted and a dummy callback installed.
hrtimer_init() will be removed as soon as all of its users have been
converted to the new function.
Signed-off-by: Nam Cao <namcao@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/5057c1ddbfd4b92033cd93d37fe38e6b069d5ba6.1730386209.git.namcao@linutronix.de
hrtimer_init*_on_stack() is not covered by tracing when
CONFIG_DEBUG_OBJECTS_TIMERS=y.
Rework the functions similar to hrtimer_init() and hrtimer_init_sleeper()
so that the hrtimer_init() tracepoint is unconditionally available.
The rework makes hrtimer_init_sleeper() unused. Delete it.
Signed-off-by: Nam Cao <namcao@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/74528e8abf2bb96e8bee85ffacbf14e15cf89f0d.1730386209.git.namcao@linutronix.de
The timer and hrtimer soft interrupts are raised in hard interrupt
context. With threaded interrupts force enabled or on PREEMPT_RT this leads
to waking the ksoftirqd for the processing of the soft interrupt.
ksoftirqd runs as SCHED_OTHER task which means it will compete with other
tasks for CPU resources. This can introduce long delays for timer
processing on heavy loaded systems and is not desired.
Split the TIMER_SOFTIRQ and HRTIMER_SOFTIRQ processing into a dedicated
timers thread and let it run at the lowest SCHED_FIFO priority.
Wake-ups for RT tasks happen from hardirq context so only timer_list timers
and hrtimers for "regular" tasks are processed here. The higher priority
ensures that wakeups are performed before scheduling SCHED_OTHER tasks.
Using a dedicated variable to store the pending softirq bits values ensure
that the timer are not accidentally picked up by ksoftirqd and other
threaded interrupts.
It shouldn't be picked up by ksoftirqd since it runs at lower priority.
However if ksoftirqd is already running while a timer fires, then ksoftird
will be PI-boosted due to the BH-lock to ktimer's priority.
The timer thread can pick up pending softirqs from ksoftirqd but only
if the softirq load is high. It is not be desired that the picked up
softirqs are processed at SCHED_FIFO priority under high softirq load
but this can already happen by a PI-boost by a force-threaded interrupt.
[ frederic@kernel.org: rcutorture.c fixes, storm fix by introduction of
local_timers_pending() for tick_nohz_next_event() ]
[ junxiao.chang@intel.com: Ensure ktimersd gets woken up even if a
softirq is currently served. ]
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Paul E. McKenney <paulmck@kernel.org> [rcutorture]
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Link: https://lore.kernel.org/all/20241106150419.2593080-4-bigeasy@linutronix.de
Raising the timer soft interrupt is always done from hard interrupt
context, so it can be reduced to just setting the TIMER soft interrupt
flag. The soft interrupt will be invoked on return from interrupt.
Use therefore __raise_softirq_irqoff() to raise the TIMER soft interrupt,
which is a trivial optimization.
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Link: https://lore.kernel.org/all/20241106150419.2593080-3-bigeasy@linutronix.de
Raising the hrtimer soft interrupt is always done from hard interrupt
context, so it can be reduced to just setting the HRTIMER soft interrupt
flag. The soft interrupt will be invoked on return from interrupt.
Use therefore __raise_softirq_irqoff() to raise the HRTIMER soft interrupt,
which is a trivial optimization.
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Link: https://lore.kernel.org/all/20241106150419.2593080-2-bigeasy@linutronix.de
Now that the SIG_IGN problem is solved in the core code, the alarmtimer
callbacks do not require a return value anymore.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Frederic Weisbecker <frederic@kernel.org>
Link: https://lore.kernel.org/all/20241105064214.318837272@linutronix.de
Now that ignored posix timer signals are requeued and the timers are
rearmed on signal delivery the workaround to keep such timers alive and
self rearm them is not longer required.
Remove the unused alarm timer parts.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/all/20241105064214.252443020@linutronix.de
Now that ignored posix timer signals are requeued and the timers are
rearmed on signal delivery the workaround to keep such timers alive and
self rearm them is not longer required.
Remove the relevant hacks and the not longer required return values from
the related functions. The alarm timer workarounds will be cleaned up in a
separate step.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/all/20241105064214.187239060@linutronix.de
Queue posixtimers which have their signal ignored on the ignored list:
1) When the timer fires and the signal has SIG_IGN set
2) When SIG_IGN is installed via sigaction() and a timer signal
is already queued
This only happens when the signal is for a valid timer, which delivered the
signal in periodic mode. One-shot timer signals are correctly dropped.
Due to the lock order constraints (sighand::siglock nests inside
timer::lock) the signal code cannot access any of the timer fields which
are relevant to make this decision, e.g. timer::it_status.
This is addressed by establishing a protection scheme which requires to
lock both locks on the timer side for modifying decision fields in the
timer struct and therefore makes it possible for the signal delivery to
evaluate with only sighand:siglock being held:
1) Move the NULLification of timer->it_signal into the sighand::siglock
protected section of timer_delete() and check timer::it_signal in the
code path which determines whether the signal is dropped or queued on
the ignore list.
This ensures that a deleted timer cannot be moved onto the ignore
list, which would prevent it from being freed on exit() as it is not
longer in the process' posix timer list.
If the timer got moved to the ignored list before deletion then it is
removed from the ignored list under sighand lock in timer_delete().
2) Provide a new timer::it_sig_periodic flag, which gets set in the
signal queue path with both timer and sighand locks held if the timer
is actually in periodic mode at expiry time.
The ignore list code checks this flag under sighand::siglock and drops
the signal when it is not set.
If it is set, then the signal is moved to the ignored list independent
of the actual state of the timer.
When the signal is un-ignored later then the signal is moved back to
the signal queue. On signal delivery the posix timer side decides
about dropping the signal if the timer was re-armed, dis-armed or
deleted based on the signal sequence counter check.
If the thread/process exits then not yet delivered signals are
discarded which means the reference of the timer containing the
sigqueue is dropped and frees the timer.
This is way cheaper than requiring all code paths to lock
sighand::siglock of the target thread/process on any modification of
timer::it_status or going all the way and removing pending signals
from the signal queues on every rearm, disarm or delete operation.
So the protection scheme here is that on the timer side both timer::lock
and sighand::siglock have to be held for modifying
timer::it_signal
timer::it_sig_periodic
which means that on the signal side holding sighand::siglock is enough to
evaluate these fields.
In posixtimer_deliver_signal() holding timer::lock is sufficient to do the
sequence validation against timer::it_signal_seq because a concurrent
expiry is waiting on timer::lock to be released.
This completes the SIG_IGN handling and such timers are not longer self
rearmed which avoids pointless wakeups.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/all/20241105064214.120756416@linutronix.de
To handle posix timer signals on sigaction(SIG_IGN) properly, the timers
will be queued on a separate ignored list.
Add the necessary cleanup code for timer_delete() and exit_itimers().
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/all/20241105064213.987530588@linutronix.de
The posix timer signal handling uses siginfo::si_sys_private for handling
the sequence counter check. That indirection is not longer required and the
sequence count value at signal queueing time can be stored in struct
k_itimer itself.
This removes the requirement of treating siginfo::si_sys_private special as
it's now always zero as the kernel does not touch it anymore.
Suggested-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Acked-by: "Eric W. Biederman" <ebiederm@xmission.com>
Link: https://lore.kernel.org/all/20241105064213.852619866@linutronix.de
To cure the SIG_IGN handling for posix interval timers, the preallocated
sigqueue needs to be embedded into struct k_itimer to prevent life time
races of all sorts.
Now that the prerequisites are in place, embed the sigqueue into struct
k_itimer and fixup the relevant usage sites.
Aside of preparing for proper SIG_IGN handling, this spares an extra
allocation.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/all/20241105064213.719695194@linutronix.de
In preparation for handling ignored posix timer signals correctly and
embedding the sigqueue struct into struct k_itimer, hand down a pointer to
the sigqueue struct into posix_timer_deliver_signal() instead of just
having a boolean flag.
No functional change.
Suggested-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Acked-by: "Eric W. Biederman" <ebiederm@xmission.com>
Link: https://lore.kernel.org/all/20241105064213.652658158@linutronix.de
To handle posix timers which have their signal ignored via SIG_IGN properly
it is required to requeue a ignored signal for delivery when SIG_IGN is
lifted so the timer gets rearmed.
Split the required code out of send_sigqueue() so it can be reused in
context of sigaction().
While at it rename send_sigqueue() to posixtimer_send_sigqueue() so its
clear what this is about.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/all/20241105064213.586453412@linutronix.de
instead of re-evaluating the signal delivery mode everywhere.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/all/20241105064213.519086500@linutronix.de
To cure the SIG_IGN handling for posix interval timers, the preallocated
sigqueue needs to be embedded into struct k_itimer to prevent life time
races of all sorts.
To make that work correctly it needs reference counting so that timer
deletion does not free the timer prematuraly when there is a signal queued
or delivered concurrently.
Add a rcuref to the posix timer part.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/all/20241105064213.304756440@linutronix.de
POSIX CPU timer nanosleep creates a k_itimer on stack and uses the sigq
pointer to detect the nanosleep case in the expiry function.
Prepare for embedding sigqueue into struct k_itimer by using a dedicated
flag for nanosleep.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/all/20241105064213.238550394@linutronix.de
The firing flag of a posix CPU timer is tristate:
0: when the timer is not about to deliver a signal
1: when the timer has expired, but the signal has not been delivered yet
-1: when the timer was queued for signal delivery and a rearm operation
raced against it and supressed the signal delivery.
This is a pointless exercise as this can be simply expressed with a
boolean. Only if set, the signal is delivered. This makes delete and rearm
consistent with the rest of the posix timers.
Convert firing to bool and fixup the usage sites accordingly and add
comments why the timer cannot be dequeued right away.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Link: https://lore.kernel.org/all/20241105064213.172848618@linutronix.de
The handling of the timer overrun in the signal code is inconsistent as it
takes previous overruns into account. This is just wrong as after the
reprogramming of a timer the overrun count starts over from a clean state,
i.e. 0.
Don't touch info::si_overrun in send_sigqueue() and only store the overrun
value at signal delivery time, which is computed from the timer itself
relative to the expiry time.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/all/20241105064213.106738193@linutronix.de
Signals of timers which are reprogammed, disarmed or deleted can deliver
signals related to the past. The POSIX spec is blury about this:
- "The effect of disarming or resetting a timer with pending expiration
notifications is unspecified."
- "The disposition of pending signals for the deleted timer is
unspecified."
In both cases it is reasonable to expect that pending signals are
discarded. Especially in the reprogramming case it does not make sense to
account for previous overruns or to deliver a signal for a timer which has
been disarmed. This makes the behaviour consistent and understandable.
Remove the si_sys_private check from the signal delivery code and invoke
posix_timer_deliver_signal() unconditionally for posix timer related
signals.
Change posix_timer_deliver_signal() so it controls the actual signal
delivery via the return value. It now instructs the signal code to drop the
signal when:
1) The timer does not longer exist in the hash table
2) The timer signal_seq value is not the same as the si_sys_private value
which was set when the signal was queued.
This is also a preparatory change to embed the sigqueue into the k_itimer
structure, which in turn allows to remove the si_sys_private magic.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Link: https://lore.kernel.org/all/20241105064213.040348644@linutronix.de
If posix_cpu_timer_del() exits early due to task not found or sighand
invalid, it fails to clear the state of the timer. That's harmless but
inconsistent.
These early exits are accounted as successful delete. Move the update of
the timer state into the success return path, so all "successful" deletions
are handled.
Reported-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Link: https://lore.kernel.org/all/20241105064212.974053438@linutronix.de
Switch all instrumentable users of the seqcount_latch interface over to
the non-raw interface.
Co-developed-by: "Peter Zijlstra (Intel)" <peterz@infradead.org>
Signed-off-by: "Peter Zijlstra (Intel)" <peterz@infradead.org>
Signed-off-by: Marco Elver <elver@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20241104161910.780003-5-elver@google.com
Most of sched_clock()'s implementation is ineligible for instrumentation
due to relying on sched_clock_noinstr().
Split the implementation off into an __always_inline function
__sched_clock(), which is then used by the noinstr and instrumentable
version, to allow more of sched_clock() to be covered by various
instrumentation.
This will allow instrumentation with the various sanitizers (KASAN,
KCSAN, KMSAN, UBSAN). For KCSAN, we know that raw seqcount_latch usage
without annotations will result in false positive reports: tell it that
all of __sched_clock() is "atomic" for the latch reader; later changes
in this series will take care of the writers.
Co-developed-by: "Peter Zijlstra (Intel)" <peterz@infradead.org>
Signed-off-by: "Peter Zijlstra (Intel)" <peterz@infradead.org>
Signed-off-by: Marco Elver <elver@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20241104161910.780003-3-elver@google.com
Swap the writes to the odd and even copies to make the writer critical
section look like all other seqcount_latch writers.
Signed-off-by: Marco Elver <elver@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20241104161910.780003-2-elver@google.com
clocksource_delta() has two variants. One with a check for negative motion,
which is only selected by x86. This is a historic leftover as this function
was previously used in the time getter hot paths.
Since 135225a363 timekeeping_cycles_to_ns() has unconditional protection
against this as a by-product of the protection against 64bit math overflow.
clocksource_delta() is only used in the clocksource watchdog and in
timekeeping_advance(). The extra conditional there is not hurting anyone.
Remove the config option and unconditionally prevent negative motion of the
readout.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: John Stultz <jstultz@google.com>
Link: https://lore.kernel.org/all/20241031120328.599430157@linutronix.de
Since 135225a363 timekeeping_cycles_to_ns() handles large offsets which
would lead to 64bit multiplication overflows correctly. It's also protected
against negative motion of the clocksource unconditionally, which was
exclusive to x86 before.
timekeeping_advance() handles large offsets already correctly.
That means the value of CONFIG_DEBUG_TIMEKEEPING which analyzed these cases
is very close to zero. Remove all of it.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: John Stultz <jstultz@google.com>
Link: https://lore.kernel.org/all/20241031120328.536010148@linutronix.de
__run_timer_base() checks base::next_expiry without holding
base::lock. That can race with a remote CPU updating next_expiry under the
lock. This is an intentional and harmless data race, but lacks a
READ_ONCE(), so KCSAN complains about this.
Add the missing READ_ONCE(). All other places are covered already.
Fixes: 79f8b28e85 ("timers: Annotate possible non critical data race of next_expiry")
Reported-by: kernel test robot <oliver.sang@intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Link: https://lore.kernel.org/all/87a5emyqk0.ffs@tglx
Closes: https://lore.kernel.org/oe-lkp/202410301205.ef8e9743-lkp@intel.com
The generic clockevent layer now detaches and stops the underlying
clockevent from the dying CPU, unifying the tick behaviour for both
periodic and oneshot mode on offline CPUs. There is no more need for
the tick layer to care about that.
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/20241029125451.54574-4-frederic@kernel.org
The way the clockevent devices are finally stopped while a CPU is
offlining is currently chaotic. The layout being by order:
1) tick_sched_timer_dying() stops the tick and the underlying clockevent
but only for oneshot case. The periodic tick and its related
clockevent still runs.
2) tick_broadcast_offline() detaches and stops the per-cpu oneshot
broadcast and append it to the released list.
3) Some individual clockevent drivers stop the clockevents (a second time if
the tick is oneshot)
4) Once the CPU is dead, a control CPU remotely detaches and stops
(a 3rd time if oneshot mode) the CPU clockevent and adds it to the
released list.
5) The released list containing the broadcast device released on step 2)
and the remotely detached clockevent from step 4) are unregistered.
These random events can be factorized if the current clockevent is
detached and stopped by the dying CPU at the generic layer, that is
from the dying CPU:
a) Stop the tick
b) Stop/detach the underlying per-cpu oneshot broadcast clockevent
c) Stop/detach the underlying clockevent
d) Release / unregister the clockevents from b) and c)
e) Release / unregister the remaining clockevents from the dying CPU.
This part could be performed by the dying CPU
This way the drivers and the tick layer don't need to care about
clockevent operations during cpuhotplug down. This also unifies the tick
behaviour on offline CPUs between oneshot and periodic modes, avoiding
offline ticks altogether for sanity.
Adopt the simplification.
[ tglx: Remove the WARN_ON() in clockevents_register_device() as that
is called from an upcoming CPU before the CPU is marked online ]
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/20241029125451.54574-3-frederic@kernel.org
When a new clockevent device is added and replaces a previous device,
the latter is put into the released list. Then the released list is
added back.
This may look counter-intuitive but the reason is that released device
might be suitable for other uses. For example a released CPU regular
clockevent can be a better replacement for the current broadcast event.
Similarly a released broadcast clockevent can be a better replacement
for the current regular clockevent of a given CPU.
Improve comments stating about these subtleties.
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/20241029125451.54574-2-frederic@kernel.org
Right now the state tracking is done by two struct members:
- it_active:
A boolean which tracks armed/disarmed state
- it_signal_seq:
A sequence counter which is used to invalidate settings
and prevent rearming
Replace it_active with it_status and keep properly track about the states
in one place.
This allows to reuse it_signal_seq to track reprogramming, disarm and
delete operations in order to drop signals which are related to the state
previous of those operations.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/all/20241001083835.670337048@linutronix.de
Prepare for using this struct member to do a proper reprogramming and
deletion accounting so that stale signals can be dropped.
No functional change.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/all/20241001083835.611997737@linutronix.de
No point in delivering a signal from the past. POSIX does not specify the
behaviour here:
- "The effect of disarming or resetting a timer with pending expiration
notifications is unspecified."
- "The disposition of pending signals for the deleted timer is unspecified."
In both cases it is reasonable to expect that pending signals are
discarded. Especially in the reprogramming case it does not make sense to
account for previous overruns or to deliver a signal for a timer which has
been disarmed.
Drop the signal as that is conistent and understandable behaviour.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/all/20241001083835.553646280@linutronix.de
In case that a timer was reprogrammed or deleted an already pending signal
is obsolete. Right now such signals are kept around and eventually
delivered. While POSIX is blury about this:
- "The effect of disarming or resetting a timer with pending expiration
notifications is unspecified."
- "The disposition of pending signals for the deleted timer is
unspecified."
it is reasonable in both cases to expect that pending signals are discarded
as they have no meaning anymore.
Prepare the signal code to allow dropping posix timer signals.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/all/20241001083835.494416923@linutronix.de
The si_sys_private member of the siginfo which is embedded in the
preallocated sigqueue is used by the posix timer code to decide whether a
timer must be reprogrammed on signal delivery.
The handling of this is racy as a long standing comment in that code
documents. It is modified with the timer lock held, but without sighand
lock being held. The actual signal delivery code checks for it under
sighand lock without holding the timer lock.
Hand the new value to send_sigqueue() as argument and store it with sighand
lock held. This is an intermediate change to address this issue.
The arguments to this function will be cleanup in subsequent changes.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/all/20241001083835.434338954@linutronix.de
Move the itimer rearming out of the signal code and consolidate all posix
timer related functions in the signal code under one ifdef.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/all/20241001083835.314100569@linutronix.de
The details about the handling of the "normal" values were moved
to the _msecs_to_jiffies() helpers in commit ca42aaf0c8 ("time:
Refactor msecs_to_jiffies"). However, the same commit still mentioned
__msecs_to_jiffies() in the added documentation.
Thus point to _msecs_to_jiffies() instead.
Fixes: ca42aaf0c8 ("time: Refactor msecs_to_jiffies")
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/20241025110141.157205-2-ojeda@kernel.org
The documentation's intention is to compare msecs_to_jiffies() (first
sentence) with __msecs_to_jiffies() (second sentence), which is what the
original documentation did. One of the cleanups in commit f3cb80804b
("time: Fix various kernel-doc problems") may have thought the paragraph
was talking about the latter since that is what it is being documented.
Thus revert that part of the change.
Fixes: f3cb80804b ("time: Fix various kernel-doc problems")
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/20241025110141.157205-1-ojeda@kernel.org
All call sites of using TK_MIRROR flag in timekeeping_update() are
gone. The TK_MIRROR dependent code path is therefore dead code.
Remove it along with the TK_MIRROR define.
Signed-off-by: Anna-Maria Behnsen <anna-maria@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: John Stultz <jstultz@google.com>
Link: https://lore.kernel.org/all/20241009-devel-anna-maria-b4-timers-ptp-timekeeping-v2-24-554456a44a15@linutronix.de
Updates of the timekeeper can be done by operating on the shadow timekeeper
and afterwards copying the result into the real timekeeper. This has the
advantage, that the sequence count write protected region is kept as small
as possible.
Convert do_adjtimex() to use this scheme and take the opportunity to use a
scoped_guard() for locking.
That requires to have a separate function for updating the leap state so
that the update is protected by the sequence count. This also brings the
timekeeper and the shadow timekeeper in sync for this state, which was not
the case so far. That's not a correctness problem as the state is only used
at the read sides which use the real timekeeper, but it's inconsistent
nevertheless.
Signed-off-by: Anna-Maria Behnsen <anna-maria@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: John Stultz <jstultz@google.com>
Link: https://lore.kernel.org/all/20241009-devel-anna-maria-b4-timers-ptp-timekeeping-v2-23-554456a44a15@linutronix.de
Updates of the timekeeper can be done by operating on the shadow timekeeper
and afterwards copying the result into the real timekeeper. This has the
advantage, that the sequence count write protected region is kept as small
as possible.
While the sequence count held time is not relevant for the resume path as
there is no concurrency, there is no reason to have this function
different than all the other update sites.
Convert timekeeping_inject_offset() to use this scheme and cleanup the
variable declarations while at it.
As halt_fast_timekeeper() does not need protection sequence counter, it is
no problem to move it with this change outside of the sequence counter
protected area. But it still needs to be executed while holding the lock.
Signed-off-by: Anna-Maria Behnsen <anna-maria@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: John Stultz <jstultz@google.com>
Link: https://lore.kernel.org/all/20241009-devel-anna-maria-b4-timers-ptp-timekeeping-v2-22-554456a44a15@linutronix.de
Updates of the timekeeper can be done by operating on the shadow timekeeper
and afterwards copying the result into the real timekeeper. This has the
advantage, that the sequence count write protected region is kept as small
as possible.
While the sequence count held time is not relevant for the resume path as
there is no concurrency, there is no reason to have this function
different than all the other update sites.
Convert timekeeping_inject_offset() to use this scheme and cleanup the
variable declaration while at it.
Signed-off-by: Anna-Maria Behnsen <anna-maria@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: John Stultz <jstultz@google.com>
Link: https://lore.kernel.org/all/20241009-devel-anna-maria-b4-timers-ptp-timekeeping-v2-21-554456a44a15@linutronix.de
Updates of the timekeeper can be done by operating on the shadow timekeeper
and afterwards copying the result into the real timekeeper. This has the
advantage, that the sequence count write protected region is kept as small
as possible.
Convert timekeeping_inject_sleeptime64() to use this scheme.
Signed-off-by: Anna-Maria Behnsen <anna-maria@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: John Stultz <jstultz@google.com>
Link: https://lore.kernel.org/all/20241009-devel-anna-maria-b4-timers-ptp-timekeeping-v2-20-554456a44a15@linutronix.de
For timekeeping_init() the sequence count write held time is not relevant
and it could keep working on the real timekeeper, but there is no reason to
make it different from other timekeeper updates.
Convert it to operate on the shadow timekeeper.
Signed-off-by: Anna-Maria Behnsen <anna-maria@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: John Stultz <jstultz@google.com>
Link: https://lore.kernel.org/all/20241009-devel-anna-maria-b4-timers-ptp-timekeeping-v2-19-554456a44a15@linutronix.de
Updates of the timekeeper can be done by operating on the shadow timekeeper
and afterwards copying the result into the real timekeeper. This has the
advantage, that the sequence count write protected region is kept as small
as possible.
Convert change_clocksource() to use this scheme.
Signed-off-by: Anna-Maria Behnsen <anna-maria@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: John Stultz <jstultz@google.com>
Link: https://lore.kernel.org/all/20241009-devel-anna-maria-b4-timers-ptp-timekeeping-v2-18-554456a44a15@linutronix.de
Updates of the timekeeper can be done by operating on the shadow timekeeper
and afterwards copying the result into the real timekeeper. This has the
advantage, that the sequence count write protected region is kept as small
as possible.
Convert timekeeping_inject_offset() to use this scheme.
That allows to use a scoped_guard() for locking the timekeeper lock as the
usage of the shadow timekeeper allows a rollback in the error case instead
of the full timekeeper update of the original code.
Signed-off-by: Anna-Maria Behnsen <anna-maria@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: John Stultz <jstultz@google.com>
Link: https://lore.kernel.org/all/20241009-devel-anna-maria-b4-timers-ptp-timekeeping-v2-17-554456a44a15@linutronix.de
