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
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_settimeofday64() 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-v2-16-554456a44a15@linutronix.de
Functions which operate on the real timekeeper, e.g. do_settimeofday(),
have error conditions. If they are hit a full timekeeping update is still
required because the already committed operations modified the timekeeper.
When switching these functions to operate on the shadow timekeeper then the
full update can be avoided in the error case, but the modified shadow
timekeeper has to be restored.
Provide a helper function for that.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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-v2-15-554456a44a15@linutronix.de
timekeeping_advance() is the only optimized function which uses
shadow_timekeeper for updating the real timekeeper to keep the sequence
counter protected region as small as possible.
To be able to transform timekeeper updates in other functions to use the
same logic, split out functionality into a separate function
timekeeper_update_staged().
While at it, document the reason why the sequence counter must be write
held over the call to timekeeping_update() and the copying to the real
timekeeper and why using a pointer based update is suboptimal.
No functional change.
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-v2-13-554456a44a15@linutronix.de
Updates of the timekeeper are done in two ways:
1. Updating timekeeper and afterwards memcpy()'ing the result into
shadow_timekeeper using timekeeping_update(). Used everywhere for
updates except in timekeeping_advance(); the sequence counter protected
region starts before the first change to the timekeeper is done.
2. Updating shadow_timekeeper and then memcpy()'ing the result into
timekeeper. Used only by in timekeeping_advance(); The seqence counter
protected region is only around timekeeping_update() and the memcpy for
copy from shadow to timekeeper.
The second option is fast path optimized. The sequence counter protected
region is as short as possible.
As this behaviour is mainly documented by commit messages, but not in code,
it makes the not easy timekeeping code more complicated to read.
There is no reason why updates to the timekeeper can't use the optimized
version everywhere. With this, the code will be cleaner, as code is reused
instead of duplicated.
To be able to access tk_data which contains all required information, add a
pointer to tk_data as an argument to timekeeping_update(). With that
convert the comment about holding the lock into a lockdep assert.
No functional change.
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-v2-12-554456a44a15@linutronix.de
The struct tk_core uses is not reusable. As long as there is only a single
timekeeper, this is not a problem. But when the timekeeper infrastructure
will be reused for per ptp clock timekeepers, an explicit struct type is
required.
Define struct tk_data as explicit struct type for tk_core.
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-v2-10-554456a44a15@linutronix.de
timekeeper_lock protects updates to struct tk_core but is not part of
struct tk_core. As long as there is only a single timekeeper, this is not a
problem. But when the timekeeper infrastructure will be reused for per ptp
clock timekeepers, timekeeper_lock needs to be part of tk_core.
Move the lock into tk_core, move initialisation of the lock and sequence
counter into timekeeping_init() and update all users of timekeeper_lock.
As this is touching all lock sites, convert them to use:
guard(raw_spinlock_irqsave)(&tk_core.lock);
instead of lock/unlock functions whenever possible.
Suggested-by: Thomas Gleixner <tglx@linutronix.de>
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-v2-9-554456a44a15@linutronix.de
timekeeper_lock protects updates of timekeeper (tk_core). It is also used
by vdso_update_begin/end() and not only internally by the timekeeper code.
As long as there is only a single timekeeper, this works fine. But when
the timekeeper infrastructure will be reused for per ptp clock timekeepers,
timekeeper_lock needs to be part of tk_core..
Therefore encapuslate locking/unlocking of timekeeper_lock and make the
lock static.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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-v2-8-554456a44a15@linutronix.de
tk_core requires shadow_timekeeper to allow timekeeping_advance() updating
without holding the timekeeper sequence count write locked. This allows the
readers to make progress up to the actual update where the shadow
timekeeper is copied over to the real timekeeper.
As long as there is only a single timekeeper, having them separate is
fine. But when the timekeeper infrastructure will be reused for per ptp
clock timekeepers, shadow_timekeeper needs to be part of tk_core.
No functional change.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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-v2-7-554456a44a15@linutronix.de
timekeeping_advance() takes the timekeeper_lock and releases it before
returning. When an early return is required, goto statements are used to
make sure the lock is realeased properly. When the code was written the
locking guard() was not yet available.
Use the guard() to simplify the code and while at it cleanup ordering of
function variables. No functional change.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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-v2-5-554456a44a15@linutronix.de
There is no point to go through a full timekeeping update when acquiring a
module reference or enabling the new clocksource fails.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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-v2-4-554456a44a15@linutronix.de
do_adjtimex() invokes tk_update_leap_state() unconditionally even when a
previous invocation of timekeeping_update() already did that update.
Put it into the else path which is invoked when timekeeping_update() is not
called.
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-v2-3-554456a44a15@linutronix.de
hard_pps() update does not modify anything which might be required by time
readers so forcing readers out of the way during the update is a pointless
exercise.
The interaction with adjtimex() and timekeeper updates which call into the
NTP code is properly serialized by timekeeper_lock.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Anna-Maria Behnsen <anna-maria@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/20241009-devel-anna-maria-b4-timers-ptp-timekeeping-v2-2-554456a44a15@linutronix.de
Current release - regressions:
- posix-clock: Fix unbalanced locking in pc_clock_settime()
- netfilter: fix typo causing some targets not to load on IPv6
Current release - new code bugs:
- xfrm: policy: remove last remnants of pernet inexact list
Previous releases - regressions:
- core: fix races in netdev_tx_sent_queue()/dev_watchdog()
- bluetooth: fix UAF on sco_sock_timeout
- eth: hv_netvsc: fix VF namespace also in synthetic NIC NETDEV_REGISTER event
- eth: usbnet: fix name regression
- eth: be2net: fix potential memory leak in be_xmit()
- eth: plip: fix transmit path breakage
Previous releases - always broken:
- sched: deny mismatched skip_sw/skip_hw flags for actions created by classifiers
- netfilter: bpf: must hold reference on net namespace
- eth: virtio_net: fix integer overflow in stats
- eth: bnxt_en: replace ptp_lock with irqsave variant
- eth: octeon_ep: add SKB allocation failures handling in __octep_oq_process_rx()
Misc:
- MAINTAINERS: add Simon as an official reviewer
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
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Merge tag 'net-6.12-rc5' of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net
Pull networking fixes from Paolo Abeni:
"Including fixes from netfiler, xfrm and bluetooth.
Oddly this includes a fix for a posix clock regression; in our
previous PR we included a change there as a pre-requisite for
networking one. That fix proved to be buggy and requires the follow-up
included here. Thomas suggested we should send it, given we sent the
buggy patch.
Current release - regressions:
- posix-clock: Fix unbalanced locking in pc_clock_settime()
- netfilter: fix typo causing some targets not to load on IPv6
Current release - new code bugs:
- xfrm: policy: remove last remnants of pernet inexact list
Previous releases - regressions:
- core: fix races in netdev_tx_sent_queue()/dev_watchdog()
- bluetooth: fix UAF on sco_sock_timeout
- eth: hv_netvsc: fix VF namespace also in synthetic NIC
NETDEV_REGISTER event
- eth: usbnet: fix name regression
- eth: be2net: fix potential memory leak in be_xmit()
- eth: plip: fix transmit path breakage
Previous releases - always broken:
- sched: deny mismatched skip_sw/skip_hw flags for actions created by
classifiers
- netfilter: bpf: must hold reference on net namespace
- eth: virtio_net: fix integer overflow in stats
- eth: bnxt_en: replace ptp_lock with irqsave variant
- eth: octeon_ep: add SKB allocation failures handling in
__octep_oq_process_rx()
Misc:
- MAINTAINERS: add Simon as an official reviewer"
* tag 'net-6.12-rc5' of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net: (40 commits)
net: dsa: mv88e6xxx: support 4000ps cycle counter period
net: dsa: mv88e6xxx: read cycle counter period from hardware
net: dsa: mv88e6xxx: group cycle counter coefficients
net: usb: qmi_wwan: add Fibocom FG132 0x0112 composition
hv_netvsc: Fix VF namespace also in synthetic NIC NETDEV_REGISTER event
net: dsa: microchip: disable EEE for KSZ879x/KSZ877x/KSZ876x
Bluetooth: ISO: Fix UAF on iso_sock_timeout
Bluetooth: SCO: Fix UAF on sco_sock_timeout
Bluetooth: hci_core: Disable works on hci_unregister_dev
posix-clock: posix-clock: Fix unbalanced locking in pc_clock_settime()
r8169: avoid unsolicited interrupts
net: sched: use RCU read-side critical section in taprio_dump()
net: sched: fix use-after-free in taprio_change()
net/sched: act_api: deny mismatched skip_sw/skip_hw flags for actions created by classifiers
net: usb: usbnet: fix name regression
mlxsw: spectrum_router: fix xa_store() error checking
virtio_net: fix integer overflow in stats
net: fix races in netdev_tx_sent_queue()/dev_watchdog()
net: wwan: fix global oob in wwan_rtnl_policy
netfilter: xtables: fix typo causing some targets not to load on IPv6
...
Since SLOB was removed and since commit 6c6c47b063 ("mm, slab: call
kvfree_rcu_barrier() from kmem_cache_destroy()"), it is not longer
necessary to use call_rcu() when the callback only performs
kmem_cache_free(). Use kfree_rcu() directly.
The changes were made using Coccinelle.
Signed-off-by: Julia Lawall <Julia.Lawall@inria.fr>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
Link: https://lore.kernel.org/all/20241013201704.49576-12-Julia.Lawall@inria.fr
If get_clock_desc() succeeds, it calls fget() for the clockid's fd,
and get the clk->rwsem read lock, so the error path should release
the lock to make the lock balance and fput the clockid's fd to make
the refcount balance and release the fd related resource.
However the below commit left the error path locked behind resulting in
unbalanced locking. Check timespec64_valid_strict() before
get_clock_desc() to fix it, because the "ts" is not changed
after that.
Fixes: d8794ac20a ("posix-clock: Fix missing timespec64 check in pc_clock_settime()")
Acked-by: Richard Cochran <richardcochran@gmail.com>
Signed-off-by: Jinjie Ruan <ruanjinjie@huawei.com>
Acked-by: Anna-Maria Behnsen <anna-maria@linutronix.de>
[pabeni@redhat.com: fixed commit message typo]
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
- Fix another aspect of delayed dequeued tasks wrt determining their state,
i.e., whether they're runnable or blocked
- Handle delayed dequeued tasks and their migration wrt PSI properly
- Fix the situation where a delayed dequeue task gets enqueued into a new
class, which should not happen
- Fix a case where memory allocation would happen while the runqueue lock is
held, which is a no-no
- Do not over-schedule when tasks with shorter slices preempt the currently
running task
- Make sure delayed to deque entities are properly handled before unthrottling
- Other smaller cleanups and improvements
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Merge tag 'sched_urgent_for_v6.12_rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull scheduling fixes from Borislav Petkov:
- Add PREEMPT_RT maintainers
- Fix another aspect of delayed dequeued tasks wrt determining their
state, i.e., whether they're runnable or blocked
- Handle delayed dequeued tasks and their migration wrt PSI properly
- Fix the situation where a delayed dequeue task gets enqueued into a
new class, which should not happen
- Fix a case where memory allocation would happen while the runqueue
lock is held, which is a no-no
- Do not over-schedule when tasks with shorter slices preempt the
currently running task
- Make sure delayed to deque entities are properly handled before
unthrottling
- Other smaller cleanups and improvements
* tag 'sched_urgent_for_v6.12_rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
MAINTAINERS: Add an entry for PREEMPT_RT.
sched/fair: Fix external p->on_rq users
sched/psi: Fix mistaken CPU pressure indication after corrupted task state bug
sched/core: Dequeue PSI signals for blocked tasks that are delayed
sched: Fix delayed_dequeue vs switched_from_fair()
sched/core: Disable page allocation in task_tick_mm_cid()
sched/deadline: Use hrtick_enabled_dl() before start_hrtick_dl()
sched/eevdf: Fix wakeup-preempt by checking cfs_rq->nr_running
sched: Fix sched_delayed vs cfs_bandwidth
There is a warning in checkpatch script that triggers, when min and max
arguments of usleep_range_state() are in reverse order. This check does
only cover callsites which uses constants. Add this check into the code as
a WARN_ON_ONCE() to also cover callsites not using constants and fix the
mis-usage by resetting the delta to 0.
Signed-off-by: Anna-Maria Behnsen <anna-maria@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Link: https://lore.kernel.org/all/20241014-devel-anna-maria-b4-timers-flseep-v3-9-dc8b907cb62f@linutronix.de
A lot of commonly used functions for inserting a sleep or delay lack a
proper function description. Add function descriptions to all of them to
have important information in a central place close to the code.
No functional change.
Signed-off-by: Anna-Maria Behnsen <anna-maria@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Link: https://lore.kernel.org/all/20241014-devel-anna-maria-b4-timers-flseep-v3-5-dc8b907cb62f@linutronix.de
schedule_timeout*() functions do not have proper kernel-doc formatted
function descriptions. schedule_hrtimeout() and schedule_hrtimeout_range()
have a almost identical description.
Add missing function descriptions. Remove copy of function description and
add a pointer to the existing description instead.
Signed-off-by: Anna-Maria Behnsen <anna-maria@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Frederic Weisbecker <frederic@kernel.org>
Link: https://lore.kernel.org/all/20241014-devel-anna-maria-b4-timers-flseep-v3-3-dc8b907cb62f@linutronix.de
All schedule_timeout() and *sleep*() related functions are interfaces on
top of timer list timers and hrtimers to add a sleep to the code. As they
are built on top of the timer list timers and hrtimers, the [hr]timer
interfaces are already used except when queuing the timer in
schedule_timeout(). But there exists the appropriate interface add_timer()
which does the same job with an extra check for an already pending timer.
Split all those functions as they are into a separate file and use
add_timer() instead of __mod_timer() in schedule_timeout().
While at it fix minor formatting issues and a multi line printk function
call in schedule_timeout().
Signed-off-by: Anna-Maria Behnsen <anna-maria@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Frederic Weisbecker <frederic@kernel.org>
Link: https://lore.kernel.org/all/20241014-devel-anna-maria-b4-timers-flseep-v3-2-dc8b907cb62f@linutronix.de
No implementation of this hook uses the passed in timekeeper anymore.
This avoids including a non-VDSO header while building the VDSO, which can
lead to compilation errors.
Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/all/20241010-vdso-generic-arch_update_vsyscall-v1-1-7fe5a3ea4382@linutronix.de
As Andrew pointed out, it will make sense that the PTP core
checked timespec64 struct's tv_sec and tv_nsec range before calling
ptp->info->settime64().
As the man manual of clock_settime() said, if tp.tv_sec is negative or
tp.tv_nsec is outside the range [0..999,999,999], it should return EINVAL,
which include dynamic clocks which handles PTP clock, and the condition is
consistent with timespec64_valid(). As Thomas suggested, timespec64_valid()
only check the timespec is valid, but not ensure that the time is
in a valid range, so check it ahead using timespec64_valid_strict()
in pc_clock_settime() and return -EINVAL if not valid.
There are some drivers that use tp->tv_sec and tp->tv_nsec directly to
write registers without validity checks and assume that the higher layer
has checked it, which is dangerous and will benefit from this, such as
hclge_ptp_settime(), igb_ptp_settime_i210(), _rcar_gen4_ptp_settime(),
and some drivers can remove the checks of itself.
Cc: stable@vger.kernel.org
Fixes: 0606f422b4 ("posix clocks: Introduce dynamic clocks")
Acked-by: Richard Cochran <richardcochran@gmail.com>
Suggested-by: Andrew Lunn <andrew@lunn.ch>
Suggested-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Jinjie Ruan <ruanjinjie@huawei.com>
Link: https://patch.msgid.link/20241009072302.1754567-2-ruanjinjie@huawei.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Sean noted that ever since commit 152e11f6df ("sched/fair: Implement
delayed dequeue") KVM's preemption notifiers have started
mis-classifying preemption vs blocking.
Notably p->on_rq is no longer sufficient to determine if a task is
runnable or blocked -- the aforementioned commit introduces tasks that
remain on the runqueue even through they will not run again, and
should be considered blocked for many cases.
Add the task_is_runnable() helper to classify things and audit all
external users of the p->on_rq state. Also add a few comments.
Fixes: 152e11f6df ("sched/fair: Implement delayed dequeue")
Reported-by: Sean Christopherson <seanjc@google.com>
Tested-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lkml.kernel.org/r/20241010091843.GK33184@noisy.programming.kicks-ass.net
clocksource_change_rating() has been unused since 2017's commit
63ed4e0c67 ("Drivers: hv: vmbus: Consolidate all Hyper-V specific clocksource code")
Remove it.
__clocksource_change_rating now only has one use which is ifdef'd.
Move it into the ifdef'd section.
Signed-off-by: Dr. David Alan Gilbert <linux@treblig.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/20241010135446.213098-1-linux@treblig.org
The mgtime_floor value is a global variable for tracking the latest
fine-grained timestamp handed out. Because it's a global, track the
number of times that a new floor value is assigned.
Add a new percpu counter to the timekeeping code to track the number of
floor swap events that have occurred. A later patch will add a debugfs
file to display this counter alongside other stats involving multigrain
timestamps.
Signed-off-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Randy Dunlap <rdunlap@infradead.org> # documentation bits
Link: https://lore.kernel.org/all/20241002-mgtime-v10-2-d1c4717f5284@kernel.org
Signed-off-by: Christian Brauner <brauner@kernel.org>
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
[1].
To prevent this, maintain a floor value 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.
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.
Add two new public interfaces:
- ktime_get_coarse_real_ts64_mg() fills a timespec64 with the later of the
coarse-grained clock and the floor time
- 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 floor value is global and updated via a single try_cmpxchg(). If
that fails then the operation raced with a concurrent update. Any
concurrent update must be later than the existing floor value, so any
racing tasks can accept any resulting floor value without retrying.
[1]: POSIX requires that files be stamped with realtime clock values, and
makes no provision for dealing with backward clock jumps. If a backward
realtime clock jump occurs, then files can appear to have been modified
in reverse order.
Signed-off-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Randy Dunlap <rdunlap@infradead.org> # documentation bits
Acked-by: John Stultz <jstultz@google.com>
Link: https://lore.kernel.org/all/20241002-mgtime-v10-1-d1c4717f5284@kernel.org
Signed-off-by: Christian Brauner <brauner@kernel.org>
The mgtime_floor value is a global variable for tracking the latest
fine-grained timestamp handed out. Because it's a global, track the
number of times that a new floor value is assigned.
Add a new percpu counter to the timekeeping code to track the number of
floor swap events that have occurred. A later patch will add a debugfs
file to display this counter alongside other stats involving multigrain
timestamps.
Signed-off-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Randy Dunlap <rdunlap@infradead.org> # documentation bits
Link: https://lore.kernel.org/all/20241002-mgtime-v10-2-d1c4717f5284@kernel.org
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
[1].
To prevent this, maintain a floor value 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.
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.
Add two new public interfaces:
- ktime_get_coarse_real_ts64_mg() fills a timespec64 with the later of the
coarse-grained clock and the floor time
- 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 floor value is global and updated via a single try_cmpxchg(). If
that fails then the operation raced with a concurrent update. Any
concurrent update must be later than the existing floor value, so any
racing tasks can accept any resulting floor value without retrying.
[1]: POSIX requires that files be stamped with realtime clock values, and
makes no provision for dealing with backward clock jumps. If a backward
realtime clock jump occurs, then files can appear to have been modified
in reverse order.
Signed-off-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Randy Dunlap <rdunlap@infradead.org> # documentation bits
Acked-by: John Stultz <jstultz@google.com>
Link: https://lore.kernel.org/all/20241002-mgtime-v10-1-d1c4717f5284@kernel.org
ktime_mono_to_any() only fetches the offset inside the loop. This is a
single word on 64-bit CPUs, and seqcount_read_begin() implies a full SMP
barrier.
Use READ_ONCE() to fetch the offset instead of doing a seqcount loop on
64-bit and add the matching WRITE_ONCE()'s to update the offsets in
tk_set_wall_to_mono() and tk_update_sleep_time().
[ tglx: Get rid of the #ifdeffery ]
Signed-off-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/20240910-mgtime-v3-1-84406ed53fad@kernel.org
For tracing purpose, the boot clock is interesting as it doesn't stop on
suspend. Export it as part of the time snapshot. This will later allow
the hypervisor to add boot clock timestamps to its events.
Signed-off-by: Vincent Donnefort <vdonnefort@google.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: John Stultz <jstultz@google.com>
Link: https://lore.kernel.org/all/20240911093029.3279154-5-vdonnefort@google.com
All NTP data is held in static variables. That prevents the NTP code from
being reuasble for non-system time timekeepers, e.g. per PTP clock
timekeeping.
Introduce struct ntp_data and move tick_usec into it for a start.
No functional change.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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/20240911-devel-anna-maria-b4-timers-ptp-ntp-v1-7-2d52f4e13476@linutronix.de
The reference time is required twice in ntp_update_offset(). It will not
change in the meantime as the calling code holds the timekeeper lock. Read
it only once and store it into a local variable.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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/20240911-devel-anna-maria-b4-timers-ptp-ntp-v1-6-2d52f4e13476@linutronix.de
is_error_status() and ntp_synced() return whether a state is set or
not. Both functions use unsigned int for it even if it would be a perfect
job for a bool.
Use bool instead of unsigned int. And while at it, move ntp_synced()
function to the place where it is used.
No functional change.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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/20240911-devel-anna-maria-b4-timers-ptp-ntp-v1-5-2d52f4e13476@linutronix.de
Code is partially formatted in a creative way which makes reading
harder. Examples are function calls over several lines where the
indentation does not start at the same height then the open bracket after
the function name.
Improve formatting but do not make a functional change.
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/20240911-devel-anna-maria-b4-timers-ptp-ntp-v1-4-2d52f4e13476@linutronix.de
Usage of different comment formatting makes fast reading and parsing the
code harder. There are several multi-line comments which do not follow the
coding style by starting with a line only containing '/*'. There are also
comments which do not start with capitals.
Clean up all those comments to be consistent and remove comments which
document the obvious.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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/20240911-devel-anna-maria-b4-timers-ptp-ntp-v1-3-2d52f4e13476@linutronix.de
There are no users of tick_usec outside of the NTP core code. Therefore
make tick_usec static.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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/20240911-devel-anna-maria-b4-timers-ptp-ntp-v1-2-2d52f4e13476@linutronix.de
no_llseek had been defined to NULL two years ago, in commit 868941b144
("fs: remove no_llseek")
To quote that commit,
At -rc1 we'll need do a mechanical removal of no_llseek -
git grep -l -w no_llseek | grep -v porting.rst | while read i; do
sed -i '/\<no_llseek\>/d' $i
done
would do it.
Unfortunately, that hadn't been done. Linus, could you do that now, so
that we could finally put that thing to rest? All instances are of the
form
.llseek = no_llseek,
so it's obviously safe.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
- Implement the SCHED_DEADLINE server infrastructure - Daniel Bristot de Oliveira's
last major contribution to the kernel:
"SCHED_DEADLINE servers can help fixing starvation issues of low priority
tasks (e.g., SCHED_OTHER) when higher priority tasks monopolize CPU
cycles. Today we have RT Throttling; DEADLINE servers should be able to
replace and improve that."
(Daniel Bristot de Oliveira, Peter Zijlstra, Joel Fernandes,
Youssef Esmat, Huang Shijie)
- Preparatory changes for sched_ext integration:
- Use set_next_task(.first) where required
- Fix up set_next_task() implementations
- Clean up DL server vs. core sched
- Split up put_prev_task_balance()
- Rework pick_next_task()
- Combine the last put_prev_task() and the first set_next_task()
- Rework dl_server
- Add put_prev_task(.next)
(Peter Zijlstra, with a fix by Tejun Heo)
- Complete the EEVDF transition and refine EEVDF scheduling:
- Implement delayed dequeue
- Allow shorter slices to wakeup-preempt
- Use sched_attr::sched_runtime to set request/slice suggestion
- Document the new feature flags
- Remove unused and duplicate-functionality fields
- Simplify & unify pick_next_task_fair()
- Misc debuggability enhancements
(Peter Zijlstra, with fixes/cleanups by Dietmar Eggemann,
Valentin Schneider and Chuyi Zhou)
- Initialize the vruntime of a new task when it is first enqueued,
resulting in significant decrease in latency of newly woken tasks.
(Zhang Qiao)
- Introduce SM_IDLE and an idle re-entry fast-path in __schedule()
(K Prateek Nayak, Peter Zijlstra)
- Clean up and clarify the usage of Clean up usage of rt_task()
(Qais Yousef)
- Preempt SCHED_IDLE entities in strict cgroup hierarchies
(Tianchen Ding)
- Clarify the documentation of time units for deadline scheduler
parameters. (Christian Loehle)
- Remove the HZ_BW chicken-bit feature flag introduced a year ago,
the original change seems to be working fine.
(Phil Auld)
- Misc fixes and cleanups (Chen Yu, Dan Carpenter, Huang Shijie,
Peilin He, Qais Yousefm and Vincent Guittot)
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Merge tag 'sched-core-2024-09-19' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull scheduler updates from Ingo Molnar:
- Implement the SCHED_DEADLINE server infrastructure - Daniel Bristot
de Oliveira's last major contribution to the kernel:
"SCHED_DEADLINE servers can help fixing starvation issues of low
priority tasks (e.g., SCHED_OTHER) when higher priority tasks
monopolize CPU cycles. Today we have RT Throttling; DEADLINE
servers should be able to replace and improve that."
(Daniel Bristot de Oliveira, Peter Zijlstra, Joel Fernandes, Youssef
Esmat, Huang Shijie)
- Preparatory changes for sched_ext integration:
- Use set_next_task(.first) where required
- Fix up set_next_task() implementations
- Clean up DL server vs. core sched
- Split up put_prev_task_balance()
- Rework pick_next_task()
- Combine the last put_prev_task() and the first set_next_task()
- Rework dl_server
- Add put_prev_task(.next)
(Peter Zijlstra, with a fix by Tejun Heo)
- Complete the EEVDF transition and refine EEVDF scheduling:
- Implement delayed dequeue
- Allow shorter slices to wakeup-preempt
- Use sched_attr::sched_runtime to set request/slice suggestion
- Document the new feature flags
- Remove unused and duplicate-functionality fields
- Simplify & unify pick_next_task_fair()
- Misc debuggability enhancements
(Peter Zijlstra, with fixes/cleanups by Dietmar Eggemann, Valentin
Schneider and Chuyi Zhou)
- Initialize the vruntime of a new task when it is first enqueued,
resulting in significant decrease in latency of newly woken tasks
(Zhang Qiao)
- Introduce SM_IDLE and an idle re-entry fast-path in __schedule()
(K Prateek Nayak, Peter Zijlstra)
- Clean up and clarify the usage of Clean up usage of rt_task()
(Qais Yousef)
- Preempt SCHED_IDLE entities in strict cgroup hierarchies
(Tianchen Ding)
- Clarify the documentation of time units for deadline scheduler
parameters (Christian Loehle)
- Remove the HZ_BW chicken-bit feature flag introduced a year ago,
the original change seems to be working fine (Phil Auld)
- Misc fixes and cleanups (Chen Yu, Dan Carpenter, Huang Shijie,
Peilin He, Qais Yousefm and Vincent Guittot)
* tag 'sched-core-2024-09-19' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (64 commits)
sched/cpufreq: Use NSEC_PER_MSEC for deadline task
cpufreq/cppc: Use NSEC_PER_MSEC for deadline task
sched/deadline: Clarify nanoseconds in uapi
sched/deadline: Convert schedtool example to chrt
sched/debug: Fix the runnable tasks output
sched: Fix sched_delayed vs sched_core
kernel/sched: Fix util_est accounting for DELAY_DEQUEUE
kthread: Fix task state in kthread worker if being frozen
sched/pelt: Use rq_clock_task() for hw_pressure
sched/fair: Move effective_cpu_util() and effective_cpu_util() in fair.c
sched/core: Introduce SM_IDLE and an idle re-entry fast-path in __schedule()
sched: Add put_prev_task(.next)
sched: Rework dl_server
sched: Combine the last put_prev_task() and the first set_next_task()
sched: Rework pick_next_task()
sched: Split up put_prev_task_balance()
sched: Clean up DL server vs core sched
sched: Fixup set_next_task() implementations
sched: Use set_next_task(.first) where required
sched/fair: Properly deactivate sched_delayed task upon class change
...
- Core:
- Overhaul of posix-timers in preparation of removing the
workaround for periodic timers which have signal delivery
ignored.
- Remove the historical extra jiffie in msleep()
msleep() adds an extra jiffie to the timeout value to ensure
minimal sleep time. The timer wheel ensures minimal sleep
time since the large rewrite to a non-cascading wheel, but the
extra jiffie in msleep() remained unnoticed. Remove it.
- Make the timer slack handling correct for realtime tasks.
The procfs interface is inconsistent and does neither reflect
reality nor conforms to the man page. Show the correct 0 slack
for real time tasks and enforce it at the core level instead of
having inconsistent individual checks in various timer setup
functions.
- The usual set of updates and enhancements all over the place.
- Drivers:
- Allow the ACPI PM timer to be turned off during suspend
- No new drivers
- The usual updates and enhancements in various drivers
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Merge tag 'timers-core-2024-09-16' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull timer updates from Thomas Gleixner:
"Core:
- Overhaul of posix-timers in preparation of removing the workaround
for periodic timers which have signal delivery ignored.
- Remove the historical extra jiffie in msleep()
msleep() adds an extra jiffie to the timeout value to ensure
minimal sleep time. The timer wheel ensures minimal sleep time
since the large rewrite to a non-cascading wheel, but the extra
jiffie in msleep() remained unnoticed. Remove it.
- Make the timer slack handling correct for realtime tasks.
The procfs interface is inconsistent and does neither reflect
reality nor conforms to the man page. Show the correct 0 slack for
real time tasks and enforce it at the core level instead of having
inconsistent individual checks in various timer setup functions.
- The usual set of updates and enhancements all over the place.
Drivers:
- Allow the ACPI PM timer to be turned off during suspend
- No new drivers
- The usual updates and enhancements in various drivers"
* tag 'timers-core-2024-09-16' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (43 commits)
ntp: Make sure RTC is synchronized when time goes backwards
treewide: Fix wrong singular form of jiffies in comments
cpu: Use already existing usleep_range()
timers: Rename next_expiry_recalc() to be unique
platform/x86:intel/pmc: Fix comment for the pmc_core_acpi_pm_timer_suspend_resume function
clocksource/drivers/jcore: Use request_percpu_irq()
clocksource/drivers/cadence-ttc: Add missing clk_disable_unprepare in ttc_setup_clockevent
clocksource/drivers/asm9260: Add missing clk_disable_unprepare in asm9260_timer_init
clocksource/drivers/qcom: Add missing iounmap() on errors in msm_dt_timer_init()
clocksource/drivers/ingenic: Use devm_clk_get_enabled() helpers
platform/x86:intel/pmc: Enable the ACPI PM Timer to be turned off when suspended
clocksource: acpi_pm: Add external callback for suspend/resume
clocksource/drivers/arm_arch_timer: Using for_each_available_child_of_node_scoped()
dt-bindings: timer: rockchip: Add rk3576 compatible
timers: Annotate possible non critical data race of next_expiry
timers: Remove historical extra jiffie for timeout in msleep()
hrtimer: Use and report correct timerslack values for realtime tasks
hrtimer: Annotate hrtimer_cpu_base_.*_expiry() for sparse.
timers: Add sparse annotation for timer_sync_wait_running().
signal: Replace BUG_ON()s
...
- Core:
- Remove a global lock in the affinity setting code
The lock protects a cpumask for intermediate results and the lock
causes a bottleneck on simultaneous start of multiple virtual
machines. Replace the lock and the static cpumask with a per CPU
cpumask which is nicely serialized by raw spinlock held when
executing this code.
- Provide support for giving a suffix to interrupt domain names.
That's required to support devices with subfunctions so that the
domain names are distinct even if they originate from the same
device node.
- The usual set of cleanups and enhancements all over the place
- Drivers:
- Support for longarch AVEC interrupt chip
- Refurbishment of the Armada driver so it can be extended for new
variants.
- The usual set of cleanups and enhancements all over the place
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Merge tag 'irq-core-2024-09-16' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull irq updates from Thomas Gleixner:
"Core:
- Remove a global lock in the affinity setting code
The lock protects a cpumask for intermediate results and the lock
causes a bottleneck on simultaneous start of multiple virtual
machines. Replace the lock and the static cpumask with a per CPU
cpumask which is nicely serialized by raw spinlock held when
executing this code.
- Provide support for giving a suffix to interrupt domain names.
That's required to support devices with subfunctions so that the
domain names are distinct even if they originate from the same
device node.
- The usual set of cleanups and enhancements all over the place
Drivers:
- Support for longarch AVEC interrupt chip
- Refurbishment of the Armada driver so it can be extended for new
variants.
- The usual set of cleanups and enhancements all over the place"
* tag 'irq-core-2024-09-16' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (73 commits)
genirq: Use cpumask_intersects()
genirq/cpuhotplug: Use cpumask_intersects()
irqchip/apple-aic: Only access system registers on SoCs which provide them
irqchip/apple-aic: Add a new "Global fast IPIs only" feature level
irqchip/apple-aic: Skip unnecessary enabling of use_fast_ipi
dt-bindings: apple,aic: Document A7-A11 compatibles
irqdomain: Use IS_ERR_OR_NULL() in irq_domain_trim_hierarchy()
genirq/msi: Use kmemdup_array() instead of kmemdup()
genirq/proc: Change the return value for set affinity permission error
genirq/proc: Use irq_move_pending() in show_irq_affinity()
genirq/proc: Correctly set file permissions for affinity control files
genirq: Get rid of global lock in irq_do_set_affinity()
genirq: Fix typo in struct comment
irqchip/loongarch-avec: Add AVEC irqchip support
irqchip/loongson-pch-msi: Prepare get_pch_msi_handle() for AVECINTC
irqchip/loongson-eiointc: Rename CPUHP_AP_IRQ_LOONGARCH_STARTING
LoongArch: Architectural preparation for AVEC irqchip
LoongArch: Move irqchip function prototypes to irq-loongson.h
irqchip/loongson-pch-msi: Switch to MSI parent domains
softirq: Remove unused 'action' parameter from action callback
...
- Make the uncertainty margin handling more robust to prevent false
positives
- Clarify comments
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Merge tag 'timers-clocksource-2024-09-16' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull clocksource watchdog updates from Thomas Gleixner:
- Make the uncertainty margin handling more robust to prevent false
positives
- Clarify comments
* tag 'timers-clocksource-2024-09-16' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
clocksource: Set cs_watchdog_read() checks based on .uncertainty_margin
clocksource: Fix comments on WATCHDOG_THRESHOLD & WATCHDOG_MAX_SKEW
clocksource: Improve comments for watchdog skew bounds
sync_hw_clock() is normally called every 11 minutes when time is
synchronized. This issue is that this periodic timer uses the REALTIME
clock, so when time moves backwards (the NTP server jumps into the past),
the timer expires late.
If the timer expires late, which can be days later, the RTC will no longer
be updated, which is an issue if the device is abruptly powered OFF during
this period. When the device will restart (when powered ON), it will have
the date prior to the ADJ_SETOFFSET call.
A normal NTP server should not jump in the past like that, but it is
possible... Another way of reproducing this issue is to use phc2sys to
synchronize the REALTIME clock with, for example, an IRIG timecode with
the source always starting at the same date (not synchronized).
Also, if the time jump in the future by less than 11 minutes, the RTC may
not be updated immediately (minor issue). Consider the following scenario:
- Time is synchronized, and sync_hw_clock() was just called (the timer
expires in 11 minutes).
- A time jump is realized in the future by a couple of minutes.
- The time is synchronized again.
- Users may expect that RTC to be updated as soon as possible, and not
after 11 minutes (for the same reason, if a power loss occurs in this
period).
Cancel periodic timer on any time jump (ADJ_SETOFFSET) greater than or
equal to 1s. The timer will be relaunched at the end of do_adjtimex() if
NTP is still considered synced. Otherwise the timer will be relaunched
later when NTP is synced. This way, when the time is synchronized again,
the RTC is updated after less than 2 seconds.
Signed-off-by: Benjamin ROBIN <dev@benjarobin.fr>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/20240908140836.203911-1-dev@benjarobin.fr
There are several comments all over the place, which uses a wrong singular
form of jiffies.
Replace 'jiffie' by 'jiffy'. No functional change.
Signed-off-by: Anna-Maria Behnsen <anna-maria@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Geert Uytterhoeven <geert@linux-m68k.org> # m68k
Link: https://lore.kernel.org/all/20240904-devel-anna-maria-b4-timers-flseep-v1-3-e98760256370@linutronix.de
next_expiry_recalc is the name of a function as well as the name of a
struct member of struct timer_base. This might lead to confusion.
Rename next_expiry_recalc() to timer_recalc_next_expiry(). No functional
change.
Signed-off-by: Anna-Maria Behnsen <anna-maria@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Link: https://lore.kernel.org/all/20240904-devel-anna-maria-b4-timers-flseep-v1-1-e98760256370@linutronix.de
Global timers could be expired remotely when the target CPU is idle. After
a remote timer expiry, the remote timer_base->next_expiry value is updated
while holding the timer_base->lock. When the formerly idle CPU becomes
active at the same time and checks whether timers need to expire, this
check is done lockless as it is on the local CPU. This could lead to a data
race, which was reported by sysbot:
https://lore.kernel.org/r/000000000000916e55061f969e14@google.com
When the value is read lockless but changed by the remote CPU, only two non
critical scenarios could happen:
1) The already update value is read -> everything is perfect
2) The old value is read -> a superfluous timer soft interrupt is raised
The same situation could happen when enqueueing a new first pinned timer by
a remote CPU also with non critical scenarios:
1) The already update value is read -> everything is perfect
2) The old value is read -> when the CPU is idle, an IPI is executed
nevertheless and when the CPU isn't idle, the updated value will be visible
on the next tick and the timer might be late one jiffie.
As this is very unlikely to happen, the overhead of doing the check under
the lock is a way more effort, than a superfluous timer soft interrupt or a
possible 1 jiffie delay of the timer.
Document and annotate this non critical behavior in the code by using
READ/WRITE_ONCE() pair when accessing timer_base->next_expiry.
Reported-by: syzbot+bf285fcc0a048e028118@syzkaller.appspotmail.com
Signed-off-by: Anna-Maria Behnsen <anna-maria@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Link: https://lore.kernel.org/all/20240829154305.19259-1-anna-maria@linutronix.de
Closes: https://lore.kernel.org/lkml/000000000000916e55061f969e14@google.com
msleep() and msleep_interruptible() add a jiffie to the requested timeout.
This extra jiffie was introduced to ensure that the timeout will not happen
earlier than specified.
Since the rework of the timer wheel, the enqueue path already takes care of
this. So the extra jiffie added by msleep*() is pointless now.
Remove this extra jiffie in msleep() and msleep_interruptible().
Signed-off-by: Anna-Maria Behnsen <anna-maria@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Link: https://lore.kernel.org/all/20240829074133.4547-1-anna-maria@linutronix.de
The timerslack_ns setting is used to specify how much the hardware
timers should be delayed, to potentially dispatch multiple timers in a
single interrupt. This is a performance optimization. Timers of
realtime tasks (having a realtime scheduling policy) should not be
delayed.
This logic was inconsitently applied to the hrtimers, leading to delays
of realtime tasks which used timed waits for events (e.g. condition
variables). Due to the downstream override of the slack for rt tasks,
the procfs reported incorrect (non-zero) timerslack_ns values.
This is changed by setting the timer_slack_ns task attribute to 0 for
all tasks with a rt policy. By that, downstream users do not need to
specially handle rt tasks (w.r.t. the slack), and the procfs entry
shows the correct value of "0". Setting non-zero slack values (either
via procfs or PR_SET_TIMERSLACK) on tasks with a rt policy is ignored,
as stated in "man 2 PR_SET_TIMERSLACK":
Timer slack is not applied to threads that are scheduled under a
real-time scheduling policy (see sched_setscheduler(2)).
The special handling of timerslack on rt tasks in downstream users
is removed as well.
Signed-off-by: Felix Moessbauer <felix.moessbauer@siemens.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/20240814121032.368444-2-felix.moessbauer@siemens.com
When soft interrupt actions are called, they are passed a pointer to the
struct softirq action which contains the action's function pointer.
This pointer isn't useful, as the action callback already knows what
function it is. And since each callback handles a specific soft interrupt,
the callback also knows which soft interrupt number is running.
No soft interrupt action callback actually uses this parameter, so remove
it from the function pointer signature. This clarifies that soft interrupt
actions are global routines and makes it slightly cheaper to call them.
Signed-off-by: Caleb Sander Mateos <csander@purestorage.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Jens Axboe <axboe@kernel.dk>
Link: https://lore.kernel.org/all/20240815171549.3260003-1-csander@purestorage.com
The two hrtimer_cpu_base_.*_expiry() functions are wrappers around the
locking functions and sparse complains about the missing counterpart.
Add sparse annotation to denote that this bevaviour is expected.
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/20240812105326.2240000-3-bigeasy@linutronix.de
timer_sync_wait_running() first releases two locks and then acquires
them again. This is unexpected and sparse complains about it.
Add sparse annotation for timer_sync_wait_running() to note that the
locking is expected.
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/20240812105326.2240000-2-bigeasy@linutronix.de
Some find the name realtime overloaded. Use rt_or_dl() as an
alternative, hopefully better, name.
Suggested-by: Daniel Bristot de Oliveira <bristot@redhat.com>
Signed-off-by: Qais Yousef <qyousef@layalina.io>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20240610192018.1567075-4-qyousef@layalina.io
rt_task() checks if a task has RT priority. But depends on your
dictionary, this could mean it belongs to RT class, or is a 'realtime'
task, which includes RT and DL classes.
Since this has caused some confusion already on discussion [1], it
seemed a clean up is due.
I define the usage of rt_task() to be tasks that belong to RT class.
Make sure that it returns true only for RT class and audit the users and
replace the ones required the old behavior with the new realtime_task()
which returns true for RT and DL classes. Introduce similar
realtime_prio() to create similar distinction to rt_prio() and update
the users that required the old behavior to use the new function.
Move MAX_DL_PRIO to prio.h so it can be used in the new definitions.
Document the functions to make it more obvious what is the difference
between them. PI-boosted tasks is a factor that must be taken into
account when choosing which function to use.
Rename task_is_realtime() to realtime_task_policy() as the old name is
confusing against the new realtime_task().
No functional changes were intended.
[1] https://lore.kernel.org/lkml/20240506100509.GL40213@noisy.programming.kicks-ass.net/
Signed-off-by: Qais Yousef <qyousef@layalina.io>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Phil Auld <pauld@redhat.com>
Reviewed-by: "Steven Rostedt (Google)" <rostedt@goodmis.org>
Reviewed-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Link: https://lore.kernel.org/r/20240610192018.1567075-2-qyousef@layalina.io
The addition of the bases argument to clock_was_set() fixed up all call
sites correctly except for do_adjtimex(). This uses CLOCK_REALTIME
instead of CLOCK_SET_WALL as argument. CLOCK_REALTIME is 0.
As a result the effect of that clock_was_set() notification is incomplete
and might result in timers expiring late because the hrtimer code does
not re-evaluate the affected clock bases.
Use CLOCK_SET_WALL instead of CLOCK_REALTIME to tell the hrtimers code
which clock bases need to be re-evaluated.
Fixes: 17a1b8826b ("hrtimer: Add bases argument to clock_was_set()")
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/all/877ccx7igo.ffs@tglx
Using syzkaller with the recently reintroduced signed integer overflow
sanitizer produces this UBSAN report:
UBSAN: signed-integer-overflow in ../kernel/time/ntp.c:738:18
9223372036854775806 + 4 cannot be represented in type 'long'
Call Trace:
handle_overflow+0x171/0x1b0
__do_adjtimex+0x1236/0x1440
do_adjtimex+0x2be/0x740
The user supplied time_constant value is incremented by four and then
clamped to the operating range.
Before commit eea83d896e ("ntp: NTP4 user space bits update") the user
supplied value was sanity checked to be in the operating range. That change
removed the sanity check and relied on clamping after incrementing which
does not work correctly when the user supplied value is in the overflow
zone of the '+ 4' operation.
The operation requires CAP_SYS_TIME and the side effect of the overflow is
NTP getting out of sync.
Similar to the fixups for time_maxerror and time_esterror, clamp the user
space supplied value to the operating range.
[ tglx: Switch to clamping ]
Fixes: eea83d896e ("ntp: NTP4 user space bits update")
Signed-off-by: Justin Stitt <justinstitt@google.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Miroslav Lichvar <mlichvar@redhat.com>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/all/20240517-b4-sio-ntp-c-v2-1-f3a80096f36f@google.com
Closes: https://github.com/KSPP/linux/issues/352
Using syzkaller alongside the newly reintroduced signed integer overflow
sanitizer spits out this report:
UBSAN: signed-integer-overflow in ../kernel/time/ntp.c:461:16
9223372036854775807 + 500 cannot be represented in type 'long'
Call Trace:
handle_overflow+0x171/0x1b0
second_overflow+0x2d6/0x500
accumulate_nsecs_to_secs+0x60/0x160
timekeeping_advance+0x1fe/0x890
update_wall_time+0x10/0x30
time_maxerror is unconditionally incremented and the result is checked
against NTP_PHASE_LIMIT, but the increment itself can overflow, resulting
in wrap-around to negative space.
Before commit eea83d896e ("ntp: NTP4 user space bits update") the user
supplied value was sanity checked to be in the operating range. That change
removed the sanity check and relied on clamping in handle_overflow() which
does not work correctly when the user supplied value is in the overflow
zone of the '+ 500' operation.
The operation requires CAP_SYS_TIME and the side effect of the overflow is
NTP getting out of sync.
Miroslav confirmed that the input value should be clamped to the operating
range and the same applies to time_esterror. The latter is not used by the
kernel, but the value still should be in the operating range as it was
before the sanity check got removed.
Clamp them to the operating range.
[ tglx: Changed it to clamping and included time_esterror ]
Fixes: eea83d896e ("ntp: NTP4 user space bits update")
Signed-off-by: Justin Stitt <justinstitt@google.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Miroslav Lichvar <mlichvar@redhat.com>
Link: https://lore.kernel.org/all/20240517-b4-sio-ntp-usec-v2-1-d539180f2b79@google.com
Closes: https://github.com/KSPP/linux/issues/354
Right now, cs_watchdog_read() does clocksource sanity checks based
on WATCHDOG_MAX_SKEW, which sets a floor on any clocksource's
.uncertainty_margin. These sanity checks can therefore act
inappropriately for clocksources with large uncertainty margins.
One reason for a clocksource to have a large .uncertainty_margin is when
that clocksource has long read-out latency, given that it does not make
sense for the .uncertainty_margin to be smaller than the read-out latency.
With the current checks, cs_watchdog_read() could reject all normal
reads from a clocksource with long read-out latencies, such as those
from legacy clocksources that are no longer implemented in hardware.
Therefore, recast the cs_watchdog_read() checks in terms of the
.uncertainty_margin values of the clocksources involved in the timespan in
question. The first covers two watchdog reads and one cs read, so use
twice the watchdog .uncertainty_margin plus that of the cs. The second
covers only a pair of watchdog reads, so use twice the watchdog
.uncertainty_margin.
Reported-by: Borislav Petkov <bp@alien8.de>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/20240802154618.4149953-4-paulmck@kernel.org
The WATCHDOG_THRESHOLD macro is no longer used to supply a default value
for ->uncertainty_margin, but WATCHDOG_MAX_SKEW now is.
Therefore, update the comments to reflect this change.
Reported-by: Borislav Petkov <bp@alien8.de>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/all/20240802154618.4149953-3-paulmck@kernel.org
Add more detail on the rationale for bounding the clocksource
->uncertainty_margin below at about 500ppm.
Signed-off-by: Borislav Petkov <bp@alien8.de>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/20240802154618.4149953-1-paulmck@kernel.org
The current "nretries > 1 || nretries >= max_retries" check in
cs_watchdog_read() will always evaluate to true, and thus pr_warn(), if
nretries is greater than 1. The intent is instead to never warn on the
first try, but otherwise warn if the successful retry was the last retry.
Therefore, change that "||" to "&&".
Fixes: db3a34e174 ("clocksource: Retry clock read if long delays detected")
Reported-by: Borislav Petkov <bp@alien8.de>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/all/20240802154618.4149953-2-paulmck@kernel.org
The recent fix for making the take over of the broadcast timer more
reliable retrieves a per CPU pointer in preemptible context.
This went unnoticed as compilers hoist the access into the non-preemptible
region where the pointer is actually used. But of course it's valid that
the compiler keeps it at the place where the code puts it which rightfully
triggers:
BUG: using smp_processor_id() in preemptible [00000000] code:
caller is hotplug_cpu__broadcast_tick_pull+0x1c/0xc0
Move it to the actual usage site which is in a non-preemptible region.
Fixes: f7d43dd206 ("tick/broadcast: Make takeover of broadcast hrtimer reliable")
Reported-by: David Wang <00107082@163.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Yu Liao <liaoyu15@huawei.com>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/all/87ttg56ers.ffs@tglx
Rename posix_timer_event() to posix_timer_queue_signal() as this is what
the function is about.
Consolidate the requeue pending and deactivation updates into that function
as there is no point in doing this in all incarnations of posix timers.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Posix CPU timers are not updating k_itimer::it_active which makes it
impossible to base decisions in the common posix timer code on it.
Update it when queueing or dequeueing posix CPU timers.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Reviewed-by: Anna-Maria Behnsen <anna-maria@linutronix.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
hrtimer based and CPU timers have their own way to install the new interval
and to reset overrun and signal handling related data.
Create a helper function and do the same operation for all variants.
This also makes the handling of the interval consistent. It's only stored
when the timer is actually armed, i.e. timer->it_value != 0. Before that it
was stored unconditionally for posix CPU timers and conditionally for the
other posix timers.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
No requirement for a real list. Spare a few bytes.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Keeping the overrun count of the previous setup around is just wrong. The
new setting has nothing to do with the previous one and has to start from a
clean slate.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
No point in doing this all over the place.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Reviewed-by: Anna-Maria Behnsen <anna-maria@linutronix.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Avoid the late sighand lock/unlock dance when a timer is not armed to
enforce reevaluation of the timer base so that the process wide CPU timer
sampling can be disabled.
Do it right at the point where the arming decision is made which already
has sighand locked.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Reviewed-by: Anna-Maria Behnsen <anna-maria@linutronix.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
A leftover from historical code which describes fiction.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
posix_cpu_timer_set() uses @val as variable for the current time. That's
confusing at best.
Use @now as anywhere else and rewrite the confusing comment about clock
sampling.
No functional change.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
There is no point in arming SIGEV_NONE timers as they never deliver a
signal. timer_gettime() is handling the expiry time correctly and that's
all SIGEV_NONE timers care about.
Prevent arming them and remove the expiry handler code which just disarms
them.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Reviewed-by: Anna-Maria Behnsen <anna-maria@linutronix.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reuse the split out __posix_cpu_timer_get() function which does already the
right thing.
No functional change.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Reviewed-by: Anna-Maria Behnsen <anna-maria@linutronix.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Expired SIGEV_NONE oneshot timers must return 0 nsec for the expiry time in
timer_get(), but the posix CPU timer implementation returns 1 nsec.
Add the missing conditional.
This will be cleaned up in a follow up patch.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Expired SIGEV_NONE oneshot timers must return 0 nsec for the expiry time in
timer_get(), but the posix CPU timer implementation returns 1 nsec.
Add the missing conditional.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
timer_gettime() must return the remaining time to the next expiry of a
timer or 0 if the timer is not armed and no signal pending, but posix CPU
timers fail to forward a timer which is already expired.
Add the required logic to address that.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
There is no point to return the interval for timers which have been
disarmed.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
In preparation for addressing issues in the timer_get() and timer_set()
functions of posix CPU timers.
No functional change.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Reviewed-by: Anna-Maria Behnsen <anna-maria@linutronix.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
- Stop testing the group->parent pointer as it is not guaranteed to be
stable over a chain of operations by design. This includes a warning
which would be nice to have but it produces false positives due to
the racy nature of the check.
- Plug a race between CPUs going in and out of idle and a CPU hotplug
operation. The latter can create and connect a new hierarchy level
which is missed in the concurrent updates of CPUs which go into idle.
As a result the events of such a CPU might not be processed and
timers go stale.
Cure it by splitting the hotplug operation into a prepare and online
callback. The prepare callback is guaranteed to run on an online and
therefore active CPU. This CPU updates the hierarchy and being online
ensures that there is always at least one migrator active which
handles the modified hierarchy correctly when going idle. The online
callback which runs on the incoming CPU then just marks the CPU
active and brings it into operation.
- Improve tracing and polish the code further so it is more obvious
what's going on.
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Merge tag 'timers-urgent-2024-07-26' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull timer migration updates from Thomas Gleixner:
"Fixes and minor updates for the timer migration code:
- Stop testing the group->parent pointer as it is not guaranteed to
be stable over a chain of operations by design.
This includes a warning which would be nice to have but it produces
false positives due to the racy nature of the check.
- Plug a race between CPUs going in and out of idle and a CPU hotplug
operation. The latter can create and connect a new hierarchy level
which is missed in the concurrent updates of CPUs which go into
idle. As a result the events of such a CPU might not be processed
and timers go stale.
Cure it by splitting the hotplug operation into a prepare and
online callback. The prepare callback is guaranteed to run on an
online and therefore active CPU. This CPU updates the hierarchy and
being online ensures that there is always at least one migrator
active which handles the modified hierarchy correctly when going
idle. The online callback which runs on the incoming CPU then just
marks the CPU active and brings it into operation.
- Improve tracing and polish the code further so it is more obvious
what's going on"
* tag 'timers-urgent-2024-07-26' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
timers/migration: Fix grammar in comment
timers/migration: Spare write when nothing changed
timers/migration: Rename childmask by groupmask to make naming more obvious
timers/migration: Read childmask and parent pointer in a single place
timers/migration: Use a single struct for hierarchy walk data
timers/migration: Improve tracing
timers/migration: Move hierarchy setup into cpuhotplug prepare callback
timers/migration: Do not rely always on group->parent
const qualify the struct ctl_table argument in the proc_handler function
signatures. This is a prerequisite to moving the static ctl_table
structs into .rodata data which will ensure that proc_handler function
pointers cannot be modified.
This patch has been generated by the following coccinelle script:
```
virtual patch
@r1@
identifier ctl, write, buffer, lenp, ppos;
identifier func !~ "appldata_(timer|interval)_handler|sched_(rt|rr)_handler|rds_tcp_skbuf_handler|proc_sctp_do_(hmac_alg|rto_min|rto_max|udp_port|alpha_beta|auth|probe_interval)";
@@
int func(
- struct ctl_table *ctl
+ const struct ctl_table *ctl
,int write, void *buffer, size_t *lenp, loff_t *ppos);
@r2@
identifier func, ctl, write, buffer, lenp, ppos;
@@
int func(
- struct ctl_table *ctl
+ const struct ctl_table *ctl
,int write, void *buffer, size_t *lenp, loff_t *ppos)
{ ... }
@r3@
identifier func;
@@
int func(
- struct ctl_table *
+ const struct ctl_table *
,int , void *, size_t *, loff_t *);
@r4@
identifier func, ctl;
@@
int func(
- struct ctl_table *ctl
+ const struct ctl_table *ctl
,int , void *, size_t *, loff_t *);
@r5@
identifier func, write, buffer, lenp, ppos;
@@
int func(
- struct ctl_table *
+ const struct ctl_table *
,int write, void *buffer, size_t *lenp, loff_t *ppos);
```
* Code formatting was adjusted in xfs_sysctl.c to comply with code
conventions. The xfs_stats_clear_proc_handler,
xfs_panic_mask_proc_handler and xfs_deprecated_dointvec_minmax where
adjusted.
* The ctl_table argument in proc_watchdog_common was const qualified.
This is called from a proc_handler itself and is calling back into
another proc_handler, making it necessary to change it as part of the
proc_handler migration.
Co-developed-by: Thomas Weißschuh <linux@weissschuh.net>
Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
Co-developed-by: Joel Granados <j.granados@samsung.com>
Signed-off-by: Joel Granados <j.granados@samsung.com>
The wakeup value is written unconditionally in tmigr_cpu_new_timer(). When
there was no new next timer expiry that needs to be propagated, then the
value that was read before is written. This is not required.
Move the write to the place where wakeup value is changed changed.
Signed-off-by: Anna-Maria Behnsen <anna-maria@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Link: https://lore.kernel.org/r/20240716-tmigr-fixes-v4-7-757baa7803fe@linutronix.de
childmask in the group reflects the mask that is required to 'reference'
this group in the parent. When reading childmask, this might be confusing,
as this suggests, that this is the mask of the child of the group.
Clarify this by renaming childmask in the tmigr_group and tmc_group by
groupmask.
Signed-off-by: Anna-Maria Behnsen <anna-maria@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Link: https://lore.kernel.org/r/20240716-tmigr-fixes-v4-6-757baa7803fe@linutronix.de
Reading the childmask and parent pointer is required when propagating
changes through the hierarchy. At the moment this reads are spread all over
the place which makes it harder to follow.
Move those reads to a single place to keep code clean.
Signed-off-by: Anna-Maria Behnsen <anna-maria@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Link: https://lore.kernel.org/r/20240716-tmigr-fixes-v4-5-757baa7803fe@linutronix.de
Two different structs are defined for propagating data from one to another
level when walking the hierarchy. Several struct members exist in both
structs which makes generalization harder.
Merge those two structs into a single one and use it directly in
walk_groups() and the corresponding function pointers instead of
introducing pointer casting all over the place.
Signed-off-by: Anna-Maria Behnsen <anna-maria@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Link: https://lore.kernel.org/r/20240716-tmigr-fixes-v4-4-757baa7803fe@linutronix.de
Trace points of inactive and active propagation are located at the end of
the related functions. The interesting information of those trace points is
the updated group state. When trace points are not located directly at the
place where group state changed, order of trace points in traces could be
confusing.
Move inactive and active propagation trace points directly after update of
group state values.
Signed-off-by: Anna-Maria Behnsen <anna-maria@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Link: https://lore.kernel.org/r/20240716-tmigr-fixes-v4-3-757baa7803fe@linutronix.de
When a CPU comes online the first time, it is possible that a new top level
group will be created. In general all propagation is done from the bottom
to top. This minimizes complexity and prevents possible races. But when a
new top level group is created, the formely top level group needs to be
connected to the new level. This is the only time, when the direction to
propagate changes is changed: the changes are propagated from top (new top
level group) to bottom (formerly top level group).
This introduces two races (see (A) and (B)) as reported by Frederic:
(A) This race happens, when marking the formely top level group as active,
but the last active CPU of the formerly top level group goes idle. Then
it's likely that formerly group is no longer active, but marked
nevertheless as active in new top level group:
[GRP0:0]
migrator = 0
active = 0
nextevt = KTIME_MAX
/ \
0 1 .. 7
active idle
0) Hierarchy has for now only 8 CPUs and CPU 0 is the only active CPU.
[GRP1:0]
migrator = TMIGR_NONE
active = NONE
nextevt = KTIME_MAX
\
[GRP0:0] [GRP0:1]
migrator = 0 migrator = TMIGR_NONE
active = 0 active = NONE
nextevt = KTIME_MAX nextevt = KTIME_MAX
/ \
0 1 .. 7 8
active idle !online
1) CPU 8 is booting and creates a new group in first level GRP0:1 and
therefore also a new top group GRP1:0. For now the setup code proceeded
only until the connected between GRP0:1 to the new top group. The
connection between CPU8 and GRP0:1 is not yet established and CPU 8 is
still !online.
[GRP1:0]
migrator = TMIGR_NONE
active = NONE
nextevt = KTIME_MAX
/ \
[GRP0:0] [GRP0:1]
migrator = 0 migrator = TMIGR_NONE
active = 0 active = NONE
nextevt = KTIME_MAX nextevt = KTIME_MAX
/ \
0 1 .. 7 8
active idle !online
2) Setup code now connects GRP0:0 to GRP1:0 and observes while in
tmigr_connect_child_parent() that GRP0:0 is not TMIGR_NONE. So it
prepares to call tmigr_active_up() on it. It hasn't done it yet.
[GRP1:0]
migrator = TMIGR_NONE
active = NONE
nextevt = KTIME_MAX
/ \
[GRP0:0] [GRP0:1]
migrator = TMIGR_NONE migrator = TMIGR_NONE
active = NONE active = NONE
nextevt = KTIME_MAX nextevt = KTIME_MAX
/ \
0 1 .. 7 8
idle idle !online
3) CPU 0 goes idle. Since GRP0:0->parent has been updated by CPU 8 with
GRP0:0->lock held, CPU 0 observes GRP1:0 after calling
tmigr_update_events() and it propagates the change to the top (no change
there and no wakeup programmed since there is no timer).
[GRP1:0]
migrator = GRP0:0
active = GRP0:0
nextevt = KTIME_MAX
/ \
[GRP0:0] [GRP0:1]
migrator = TMIGR_NONE migrator = TMIGR_NONE
active = NONE active = NONE
nextevt = KTIME_MAX nextevt = KTIME_MAX
/ \
0 1 .. 7 8
idle idle !online
4) Now the setup code finally calls tmigr_active_up() to and sets GRP0:0
active in GRP1:0
[GRP1:0]
migrator = GRP0:0
active = GRP0:0, GRP0:1
nextevt = KTIME_MAX
/ \
[GRP0:0] [GRP0:1]
migrator = TMIGR_NONE migrator = 8
active = NONE active = 8
nextevt = KTIME_MAX nextevt = KTIME_MAX
/ \ |
0 1 .. 7 8
idle idle active
5) Now CPU 8 is connected with GRP0:1 and CPU 8 calls tmigr_active_up() out
of tmigr_cpu_online().
[GRP1:0]
migrator = GRP0:0
active = GRP0:0
nextevt = T8
/ \
[GRP0:0] [GRP0:1]
migrator = TMIGR_NONE migrator = TMIGR_NONE
active = NONE active = NONE
nextevt = KTIME_MAX nextevt = T8
/ \ |
0 1 .. 7 8
idle idle idle
5) CPU 8 goes idle with a timer T8 and relies on GRP0:0 as the migrator.
But it's not really active, so T8 gets ignored.
--> The update which is done in third step is not noticed by setup code. So
a wrong migrator is set to top level group and a timer could get
ignored.
(B) Reading group->parent and group->childmask when an hierarchy update is
ongoing and reaches the formerly top level group is racy as those values
could be inconsistent. (The notation of migrator and active now slightly
changes in contrast to the above example, as now the childmasks are used.)
[GRP1:0]
migrator = TMIGR_NONE
active = 0x00
nextevt = KTIME_MAX
\
[GRP0:0] [GRP0:1]
migrator = TMIGR_NONE migrator = TMIGR_NONE
active = 0x00 active = 0x00
nextevt = KTIME_MAX nextevt = KTIME_MAX
childmask= 0 childmask= 1
parent = NULL parent = GRP1:0
/ \
0 1 .. 7 8
idle idle !online
childmask=1
1) Hierarchy has 8 CPUs. CPU 8 is at the moment in the process of onlining
but did not yet connect GRP0:0 to GRP1:0.
[GRP1:0]
migrator = TMIGR_NONE
active = 0x00
nextevt = KTIME_MAX
/ \
[GRP0:0] [GRP0:1]
migrator = TMIGR_NONE migrator = TMIGR_NONE
active = 0x00 active = 0x00
nextevt = KTIME_MAX nextevt = KTIME_MAX
childmask= 0 childmask= 1
parent = GRP1:0 parent = GRP1:0
/ \
0 1 .. 7 8
idle idle !online
childmask=1
2) Setup code (running on CPU 8) now connects GRP0:0 to GRP1:0, updates
parent pointer of GRP0:0 and ...
[GRP1:0]
migrator = TMIGR_NONE
active = 0x00
nextevt = KTIME_MAX
/ \
[GRP0:0] [GRP0:1]
migrator = 0x01 migrator = TMIGR_NONE
active = 0x01 active = 0x00
nextevt = KTIME_MAX nextevt = KTIME_MAX
childmask= 0 childmask= 1
parent = GRP1:0 parent = GRP1:0
/ \
0 1 .. 7 8
active idle !online
childmask=1
tmigr_walk.childmask = 0
3) ... CPU 0 comes active in the same time. As migrator in GRP0:0 was
TMIGR_NONE, childmask of GRP0:0 is stored in update propagation data
structure tmigr_walk (as update of childmask is not yet
visible/updated). And now ...
[GRP1:0]
migrator = TMIGR_NONE
active = 0x00
nextevt = KTIME_MAX
/ \
[GRP0:0] [GRP0:1]
migrator = 0x01 migrator = TMIGR_NONE
active = 0x01 active = 0x00
nextevt = KTIME_MAX nextevt = KTIME_MAX
childmask= 2 childmask= 1
parent = GRP1:0 parent = GRP1:0
/ \
0 1 .. 7 8
active idle !online
childmask=1
tmigr_walk.childmask = 0
4) ... childmask of GRP0:0 is updated by CPU 8 (still part of setup
code).
[GRP1:0]
migrator = 0x00
active = 0x00
nextevt = KTIME_MAX
/ \
[GRP0:0] [GRP0:1]
migrator = 0x01 migrator = TMIGR_NONE
active = 0x01 active = 0x00
nextevt = KTIME_MAX nextevt = KTIME_MAX
childmask= 2 childmask= 1
parent = GRP1:0 parent = GRP1:0
/ \
0 1 .. 7 8
active idle !online
childmask=1
tmigr_walk.childmask = 0
5) CPU 0 sees the connection to GRP1:0 and now propagates active state to
GRP1:0 but with childmask = 0 as stored in propagation data structure.
--> Now GRP1:0 always has a migrator as 0x00 != TMIGR_NONE and for all CPUs
it looks like GRP1:0 is always active.
To prevent those races, the setup of the hierarchy is moved into the
cpuhotplug prepare callback. The prepare callback is not executed by the
CPU which will come online, it is executed by the CPU which prepares
onlining of the other CPU. This CPU is active while it is connecting the
formerly top level to the new one. This prevents from (A) to happen and it
also prevents from any further walk above the formerly top level until that
active CPU becomes inactive, releasing the new ->parent and ->childmask
updates to be visible by any subsequent walk up above the formerly top
level hierarchy. This prevents from (B) to happen. The direction for the
updates is now forced to look like "from bottom to top".
However if the active CPU prevents from tmigr_cpu_(in)active() to walk up
with the update not-or-half visible, nothing prevents walking up to the new
top with a 0 childmask in tmigr_handle_remote_up() or
tmigr_requires_handle_remote_up() if the active CPU doing the prepare is
not the migrator. But then it looks fine because:
* tmigr_check_migrator() should just return false
* The migrator is active and should eventually observe the new childmask
at some point in a future tick.
Split setup functionality of online callback into the cpuhotplug prepare
callback and setup hotplug state. Change init call into early_initcall() to
make sure an already active CPU prepares everything for newly upcoming
CPUs. Reorder the code, that all prepare related functions are close to
each other and online and offline callbacks are also close together.
Fixes: 7ee9887703 ("timers: Implement the hierarchical pull model")
Signed-off-by: Anna-Maria Behnsen <anna-maria@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Link: https://lore.kernel.org/r/20240717094940.18687-1-anna-maria@linutronix.de
When reading group->parent without holding the group lock it is racy
against CPUs coming online the first time and thereby creating another
level of the hierarchy. This is not a problem when this value is read once
to decide whether to abort a propagation or not. The worst outcome is an
unnecessary/early CPU wake up. But it is racy when reading it several times
during a single 'action' (like activation, deactivation, checking for
remote timer expiry,...) and relying on the consitency of this value
without holding the lock. This happens at the moment e.g. in
tmigr_inactive_up() which is also calling tmigr_udpate_events(). Code relys
on group->parent not to change during this 'action'.
Update parent struct member description to explain the above only
once. Remove parent pointer checks when they are not mandatory (like update
of data->childmask). Remove a warning, which would be nice but the trigger
of this warning is not reliable and add expand the data structure member
description instead. Expand a comment, why it is safe to rely on parent
pointer here (inside hierarchy update).
Fixes: 7ee9887703 ("timers: Implement the hierarchical pull model")
Reported-by: Borislav Petkov <bp@alien8.de>
Signed-off-by: Anna-Maria Behnsen <anna-maria@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Link: https://lore.kernel.org/r/20240716-tmigr-fixes-v4-1-757baa7803fe@linutronix.de
initialized in the code path anyway right after on the ARM arch
timer and the ARM global timer (Li kunyu)
- Fix a race condition in the interrupt leading to a deadlock on the
SH CMT driver. Note that this fix was not tested on the platform
using this timer but the fix seems reasonable enough to be picked
confidently (Niklas Söderlund)
- Increase the rating of the gic-timer and use the configured width
clocksource register on the MIPS architecture (Jiaxun Yang)
- Add the DT bindings for the TMU on the Renesas platforms (Geert
Uytterhoeven)
- Add the DT bindings for the SOPHGO SG2002 clint on RiscV (Thomas
Bonnefille)
- Add the rtl-otto timer driver along with the DT bindings for the
Realtek platform (Chris Packham)
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Merge tag 'timers-v6.11-rc1' of https://git.linaro.org/people/daniel.lezcano/linux into timers/core
Pull clocksource/event driver updates from Daniel Lezcano:
- Remove unnecessary local variables initialization as they will be
initialized in the code path anyway right after on the ARM arch
timer and the ARM global timer (Li kunyu)
- Fix a race condition in the interrupt leading to a deadlock on the
SH CMT driver. Note that this fix was not tested on the platform
using this timer but the fix seems reasonable enough to be picked
confidently (Niklas Söderlund)
- Increase the rating of the gic-timer and use the configured width
clocksource register on the MIPS architecture (Jiaxun Yang)
- Add the DT bindings for the TMU on the Renesas platforms (Geert
Uytterhoeven)
- Add the DT bindings for the SOPHGO SG2002 clint on RiscV (Thomas
Bonnefille)
- Add the rtl-otto timer driver along with the DT bindings for the
Realtek platform (Chris Packham)
Link: https://lore.kernel.org/all/91cd05de-4c5d-4242-a381-3b8a4fe6a2a2@linaro.org
Running the LTP hotplug stress test on a aarch64 machine results in
rcu_sched stall warnings when the broadcast hrtimer was owned by the
un-plugged CPU. The issue is the following:
CPU1 (owns the broadcast hrtimer) CPU2
tick_broadcast_enter()
// shutdown local timer device
broadcast_shutdown_local()
...
tick_broadcast_exit()
clockevents_switch_state(dev, CLOCK_EVT_STATE_ONESHOT)
// timer device is not programmed
cpumask_set_cpu(cpu, tick_broadcast_force_mask)
initiates offlining of CPU1
take_cpu_down()
/*
* CPU1 shuts down and does not
* send broadcast IPI anymore
*/
takedown_cpu()
hotplug_cpu__broadcast_tick_pull()
// move broadcast hrtimer to this CPU
clockevents_program_event()
bc_set_next()
hrtimer_start()
/*
* timer device is not programmed
* because only the first expiring
* timer will trigger clockevent
* device reprogramming
*/
What happens is that CPU2 exits broadcast mode with force bit set, then the
local timer device is not reprogrammed and CPU2 expects to receive the
expired event by the broadcast IPI. But this does not happen because CPU1
is offlined by CPU2. CPU switches the clockevent device to ONESHOT state,
but does not reprogram the device.
The subsequent reprogramming of the hrtimer broadcast device does not
program the clockevent device of CPU2 either because the pending expiry
time is already in the past and the CPU expects the event to be delivered.
As a consequence all CPUs which wait for a broadcast event to be delivered
are stuck forever.
Fix this issue by reprogramming the local timer device if the broadcast
force bit of the CPU is set so that the broadcast hrtimer is delivered.
[ tglx: Massage comment and change log. Add Fixes tag ]
Fixes: 989dcb645c ("tick: Handle broadcast wakeup of multiple cpus")
Signed-off-by: Yu Liao <liaoyu15@huawei.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20240711124843.64167-1-liaoyu15@huawei.com
When the WARN_ON_ONCE() triggers, the printk() of the additional
information related to the warning will not happen in print level
"warn". When reading dmesg with a restriction to level "warn", the
information published by the printk_once() will not show up there.
Transform WARN_ON_ONCE() and printk_once() into a WARN_ONCE().
Signed-off-by: Anna-Maria Behnsen <anna-maria@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Link: https://lore.kernel.org/r/20240610103552.25252-1-anna-maria@linutronix.de
The hrtimer function callback must not be NULL. It has to be specified by
the call side but it is not validated by the hrtimer code. When a hrtimer
is queued without a function callback, the kernel crashes with a null
pointer dereference when trying to execute the callback in __run_hrtimer().
Introduce a validation before queuing the hrtimer in
hrtimer_start_range_ns().
[anna-maria: Rephrase commit message]
Signed-off-by: Phil Chang <phil.chang@mediatek.com>
Signed-off-by: Anna-Maria Behnsen <anna-maria@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Anna-Maria Behnsen <anna-maria@linutronix.de>
The function returns the idle calls counter for the current cpu and
therefore usually isn't what the caller wants. It is unnused since
commit 466a2b42d6 ("cpufreq: schedutil: Use idle_calls counter of the
remote CPU")
Signed-off-by: Christian Loehle <christian.loehle@arm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20240617161615.49309-1-christian.loehle@arm.com
After the recent commit 5097cbcb38 ("sched/isolation: Prevent boot crash
when the boot CPU is nohz_full") the kernel no longer crashes, but there is
another problem.
In this case tick_setup_device() calls tick_take_do_timer_from_boot() to
update tick_do_timer_cpu and this triggers the WARN_ON_ONCE(irqs_disabled)
in smp_call_function_single().
Kill tick_take_do_timer_from_boot() and just use WRITE_ONCE(), the new
comment explains why this is safe (thanks Thomas!).
Fixes: 08ae95f4fd ("nohz_full: Allow the boot CPU to be nohz_full")
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20240528122019.GA28794@redhat.com
Link: https://lore.kernel.org/all/20240522151742.GA10400@redhat.com
PPS (Pulse Per Second) generates a hardware pulse every second based on
CLOCK_REALTIME. This works fine when the pulse is generated in software
from a hrtimer callback function.
For hardware which generates the pulse by programming a timer it is
required to convert CLOCK_REALTIME to the underlying hardware clock.
The X86 Timed IO device is based on the Always Running Timer (ART), which
is the base clock of the TSC, which is usually the system clocksource on
X86.
The core code already has functionality to convert base clock timestamps to
system clocksource timestamps, but there is no support for converting the
other way around.
Provide the required functionality to support such devices in a generic
way to avoid code duplication in drivers:
1) ktime_real_to_base_clock() to convert a CLOCK_REALTIME timestamp to a
base clock timestamp
2) timekeeping_clocksource_has_base() to allow drivers to validate that
the system clocksource is based on a particular clocksource ID.
[ tglx: Simplify timekeeping_clocksource_has_base() and add missing READ_ONCE() ]
Co-developed-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Co-developed-by: Christopher S. Hall <christopher.s.hall@intel.com>
Signed-off-by: Christopher S. Hall <christopher.s.hall@intel.com>
Signed-off-by: Lakshmi Sowjanya D <lakshmi.sowjanya.d@intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20240513103813.5666-10-lakshmi.sowjanya.d@intel.com
Hardware time stamps like provided by PTP clock implementations are based
on a clock which feeds both the PCIe device and the system clock. For
further processing the underlying hardwarre clock timestamp must be
converted to the system clock.
Right now this requires drivers to invoke an architecture specific
conversion function, e.g. to convert the ART (Always Running Timer)
timestamp to a TSC timestamp.
As the system clock is aware of the underlying base clock, this can be
moved to the core code by providing a base clock property for the system
clock which contains the conversion factors and assigning a clocksource ID
to the base clock.
Add the required data structures and the conversion infrastructure in the
core code to prepare for converting X86 and the related PTP drivers over.
[ tglx: Added a missing READ_ONCE(). Massaged change log ]
Co-developed-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Co-developed-by: Christopher S. Hall <christopher.s.hall@intel.com>
Signed-off-by: Christopher S. Hall <christopher.s.hall@intel.com>
Signed-off-by: Lakshmi Sowjanya D <lakshmi.sowjanya.d@intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20240513103813.5666-2-lakshmi.sowjanya.d@intel.com
Fix the make W=1 warnings:
WARNING: modpost: missing MODULE_DESCRIPTION() in kernel/time/clocksource-wdtest.o
WARNING: modpost: missing MODULE_DESCRIPTION() in kernel/time/test_udelay.o
WARNING: modpost: missing MODULE_DESCRIPTION() in kernel/time/time_test.o
Signed-off-by: Jeff Johnson <quic_jjohnson@quicinc.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Paul E. McKenney <paulmck@kernel.org>
Link: https://lore.kernel.org/r/20240510-time-md-v1-1-44a8a36ac4b0@quicinc.com
Summary
* Removed sentinel elements from ctl_table structs in kernel/*
Removing sentinels in ctl_table arrays reduces the build time size and
runtime memory consumed by ~64 bytes per array. Removals for net/, io_uring/,
mm/, ipc/ and security/ are set to go into mainline through their respective
subsystems making the next release the most likely place where the final
series that removes the check for proc_name == NULL will land. This PR adds
to removals already in arch/, drivers/ and fs/.
* Adjusted ctl_table definitions and references to allow constification
Adjustments:
- Removing unused ctl_table function arguments
- Moving non-const elements from ctl_table to ctl_table_header
- Making ctl_table pointers const in ctl_table_root structure
Making the static ctl_table structs const will increase safety by keeping the
pointers to proc_handler functions in .rodata. Though no ctl_tables where
made const in this PR, the ground work for making that possible has started
with these changes sent by Thomas Weißschuh.
Testing
* These changes went into linux-next after v6.9-rc4; giving it a good month of
testing.
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Merge tag 'sysctl-6.10-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/sysctl/sysctl
Pull sysctl updates from Joel Granados:
- Remove sentinel elements from ctl_table structs in kernel/*
Removing sentinels in ctl_table arrays reduces the build time size
and runtime memory consumed by ~64 bytes per array. Removals for
net/, io_uring/, mm/, ipc/ and security/ are set to go into mainline
through their respective subsystems making the next release the most
likely place where the final series that removes the check for
proc_name == NULL will land.
This adds to removals already in arch/, drivers/ and fs/.
- Adjust ctl_table definitions and references to allow constification
- Remove unused ctl_table function arguments
- Move non-const elements from ctl_table to ctl_table_header
- Make ctl_table pointers const in ctl_table_root structure
Making the static ctl_table structs const will increase safety by
keeping the pointers to proc_handler functions in .rodata. Though no
ctl_tables where made const in this PR, the ground work for making
that possible has started with these changes sent by Thomas
Weißschuh.
* tag 'sysctl-6.10-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/sysctl/sysctl:
sysctl: drop now unnecessary out-of-bounds check
sysctl: move sysctl type to ctl_table_header
sysctl: drop sysctl_is_perm_empty_ctl_table
sysctl: treewide: constify argument ctl_table_root::permissions(table)
sysctl: treewide: drop unused argument ctl_table_root::set_ownership(table)
bpf: Remove the now superfluous sentinel elements from ctl_table array
delayacct: Remove the now superfluous sentinel elements from ctl_table array
kprobes: Remove the now superfluous sentinel elements from ctl_table array
printk: Remove the now superfluous sentinel elements from ctl_table array
scheduler: Remove the now superfluous sentinel elements from ctl_table array
seccomp: Remove the now superfluous sentinel elements from ctl_table array
timekeeping: Remove the now superfluous sentinel elements from ctl_table array
ftrace: Remove the now superfluous sentinel elements from ctl_table array
umh: Remove the now superfluous sentinel elements from ctl_table array
kernel misc: Remove the now superfluous sentinel elements from ctl_table array
- Core code:
- Make timekeeping and VDSO time readouts resilent against math overflow:
In guest context the kernel is prone to math overflow when the host
defers the timer interrupt due to overload, malfunction or malice.
This can be mitigated by checking the clocksource delta for the
maximum deferrement which is readily available. If that value is
exceeded then the code uses a slowpath function which can handle the
multiplication overflow.
This functionality is enabled unconditionally in the kernel, but made
conditional in the VDSO code. The latter is conditional because it
allows architectures to optimize the check so it is not causing
performance regressions.
On X86 this is achieved by reworking the existing check for negative
TSC deltas as a negative delta obviously exceeds the maximum
deferrement when it is evaluated as an unsigned value. That avoids two
conditionals in the hotpath and allows to hide both the negative delta
and the large delta handling in the same slow path.
- Add an initial minimal ktime_t abstraction for Rust
- The usual boring cleanups and enhancements
- Drivers:
- Boring updates to device trees and trivial enhancements in various
drivers.
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Merge tag 'timers-core-2024-05-12' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull timers and timekeeping updates from Thomas Gleixner:
"Core code:
- Make timekeeping and VDSO time readouts resilent against math
overflow:
In guest context the kernel is prone to math overflow when the host
defers the timer interrupt due to overload, malfunction or malice.
This can be mitigated by checking the clocksource delta for the
maximum deferrement which is readily available. If that value is
exceeded then the code uses a slowpath function which can handle
the multiplication overflow.
This functionality is enabled unconditionally in the kernel, but
made conditional in the VDSO code. The latter is conditional
because it allows architectures to optimize the check so it is not
causing performance regressions.
On X86 this is achieved by reworking the existing check for
negative TSC deltas as a negative delta obviously exceeds the
maximum deferrement when it is evaluated as an unsigned value. That
avoids two conditionals in the hotpath and allows to hide both the
negative delta and the large delta handling in the same slow path.
- Add an initial minimal ktime_t abstraction for Rust
- The usual boring cleanups and enhancements
Drivers:
- Boring updates to device trees and trivial enhancements in various
drivers"
* tag 'timers-core-2024-05-12' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (33 commits)
clocksource/drivers/arm_arch_timer: Mark hisi_161010101_oem_info const
clocksource/drivers/timer-ti-dm: Remove an unused field in struct dmtimer
clocksource/drivers/renesas-ostm: Avoid reprobe after successful early probe
clocksource/drivers/renesas-ostm: Allow OSTM driver to reprobe for RZ/V2H(P) SoC
dt-bindings: timer: renesas: ostm: Document Renesas RZ/V2H(P) SoC
rust: time: doc: Add missing C header links
clocksource: Make the int help prompt unit readable in ncurses
hrtimer: Rename __hrtimer_hres_active() to hrtimer_hres_active()
timerqueue: Remove never used function timerqueue_node_expires()
rust: time: Add Ktime
vdso: Fix powerpc build U64_MAX undeclared error
clockevents: Convert s[n]printf() to sysfs_emit()
clocksource: Convert s[n]printf() to sysfs_emit()
clocksource: Make watchdog and suspend-timing multiplication overflow safe
timekeeping: Let timekeeping_cycles_to_ns() handle both under and overflow
timekeeping: Make delta calculation overflow safe
timekeeping: Prepare timekeeping_cycles_to_ns() for overflow safety
timekeeping: Fold in timekeeping_delta_to_ns()
timekeeping: Consolidate timekeeping helpers
timekeeping: Refactor timekeeping helpers
...
- Add cpufreq pressure feedback for the scheduler
- Rework misfit load-balancing wrt. affinity restrictions
- Clean up and simplify the code around ::overutilized and
::overload access.
- Simplify sched_balance_newidle()
- Bump SCHEDSTAT_VERSION to 16 due to a cleanup of CPU_MAX_IDLE_TYPES
handling that changed the output.
- Rework & clean up <asm/vtime.h> interactions wrt. arch_vtime_task_switch()
- Reorganize, clean up and unify most of the higher level
scheduler balancing function names around the sched_balance_*()
prefix.
- Simplify the balancing flag code (sched_balance_running)
- Miscellaneous cleanups & fixes
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Merge tag 'sched-core-2024-05-13' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull scheduler updates from Ingo Molnar:
- Add cpufreq pressure feedback for the scheduler
- Rework misfit load-balancing wrt affinity restrictions
- Clean up and simplify the code around ::overutilized and
::overload access.
- Simplify sched_balance_newidle()
- Bump SCHEDSTAT_VERSION to 16 due to a cleanup of CPU_MAX_IDLE_TYPES
handling that changed the output.
- Rework & clean up <asm/vtime.h> interactions wrt arch_vtime_task_switch()
- Reorganize, clean up and unify most of the higher level
scheduler balancing function names around the sched_balance_*()
prefix
- Simplify the balancing flag code (sched_balance_running)
- Miscellaneous cleanups & fixes
* tag 'sched-core-2024-05-13' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (50 commits)
sched/pelt: Remove shift of thermal clock
sched/cpufreq: Rename arch_update_thermal_pressure() => arch_update_hw_pressure()
thermal/cpufreq: Remove arch_update_thermal_pressure()
sched/cpufreq: Take cpufreq feedback into account
cpufreq: Add a cpufreq pressure feedback for the scheduler
sched/fair: Fix update of rd->sg_overutilized
sched/vtime: Do not include <asm/vtime.h> header
s390/irq,nmi: Include <asm/vtime.h> header directly
s390/vtime: Remove unused __ARCH_HAS_VTIME_TASK_SWITCH leftover
sched/vtime: Get rid of generic vtime_task_switch() implementation
sched/vtime: Remove confusing arch_vtime_task_switch() declaration
sched/balancing: Simplify the sg_status bitmask and use separate ->overloaded and ->overutilized flags
sched/fair: Rename set_rd_overutilized_status() to set_rd_overutilized()
sched/fair: Rename SG_OVERLOAD to SG_OVERLOADED
sched/fair: Rename {set|get}_rd_overload() to {set|get}_rd_overloaded()
sched/fair: Rename root_domain::overload to ::overloaded
sched/fair: Use helper functions to access root_domain::overload
sched/fair: Check root_domain::overload value before update
sched/fair: Combine EAS check with root_domain::overutilized access
sched/fair: Simplify the continue_balancing logic in sched_balance_newidle()
...
When tmigr_setup_groups() fails the level 0 group allocation, then the
cleanup derefences index -1 of the local stack array.
Prevent this by checking the loop condition first.
Fixes: 7ee9887703 ("timers: Implement the hierarchical pull model")
Signed-off-by: Levi Yun <ppbuk5246@gmail.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Anna-Maria Behnsen <anna-maria@linutronix.de>
Link: https://lore.kernel.org/r/20240506041059.86877-1-ppbuk5246@gmail.com
When doing
make menuconfig
and searching for the CLOCKSOURCE_WATCHDOG_MAX_SKEW_US config item, the
help says:
│ Symbol: CLOCKSOURCE_WATCHDOG_MAX_SKEW_US [=125]
│ Type : integer
│ Range : [50 1000]
│ Defined at kernel/time/Kconfig:204
│ Prompt: Clocksource watchdog maximum allowable skew (in s)
^^^
│ Depends on: GENERIC_CLOCKEVENTS [=y] && CLOCKSOURCE_WATCHDOG [=y]
because on some terminals, it cannot display the 'μ' char, unicode
number 0x3bc.
So simply write it out so that there's no trouble.
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Paul E. McKenney <paulmck@kernel.org>
Acked-by: Randy Dunlap <rdunlap@infradead.org>
Link: https://lore.kernel.org/r/20240428102143.26764-1-bp@kernel.org
This commit comes at the tail end of a greater effort to remove the
empty elements at the end of the ctl_table arrays (sentinels) which
will reduce the overall build time size of the kernel and run time
memory bloat by ~64 bytes per sentinel (further information Link :
https://lore.kernel.org/all/ZO5Yx5JFogGi%2FcBo@bombadil.infradead.org/)
Remove sentinel element from time_sysctl
Signed-off-by: Joel Granados <j.granados@samsung.com>
The function hrtimer_hres_active() are defined in the hrtimer.c file, but
not called elsewhere, so rename __hrtimer_hres_active() to
hrtimer_hres_active() and remove the old hrtimer_hres_active() function.
kernel/time/hrtimer.c:653:19: warning: unused function 'hrtimer_hres_active'.
Fixes: 82ccdf062a ("hrtimer: Remove unused function")
Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Signed-off-by: Jiapeng Chong <jiapeng.chong@linux.alibaba.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Anna-Maria Behnsen <anna-maria@linutronix.de>
Link: https://lore.kernel.org/r/20240418023000.130324-1-jiapeng.chong@linux.alibaba.com
Closes: https://bugzilla.openanolis.cn/show_bug.cgi?id=8778
tick_do_timer_cpu is used lockless to check which CPU needs to take care
of the per tick timekeeping duty. This is done to avoid a thundering
herd problem on jiffies_lock.
The read and writes are not annotated so KCSAN complains about data races:
BUG: KCSAN: data-race in tick_nohz_idle_stop_tick / tick_nohz_next_event
write to 0xffffffff8a2bda30 of 4 bytes by task 0 on cpu 26:
tick_nohz_idle_stop_tick+0x3b1/0x4a0
do_idle+0x1e3/0x250
read to 0xffffffff8a2bda30 of 4 bytes by task 0 on cpu 16:
tick_nohz_next_event+0xe7/0x1e0
tick_nohz_get_sleep_length+0xa7/0xe0
menu_select+0x82/0xb90
cpuidle_select+0x44/0x60
do_idle+0x1c2/0x250
value changed: 0x0000001a -> 0xffffffff
Annotate them with READ/WRITE_ONCE() to document the intentional data race.
Reported-by: Mirsad Todorovac <mirsad.todorovac@alu.unizg.hr>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Tested-by: Sean Anderson <sean.anderson@seco.com>
Link: https://lore.kernel.org/r/87cyqy7rt3.ffs@tglx
