Nicolas Saenz Julienne 42aaf726c9 tracing/osnoise: Force quiescent states while tracing ... commit caf4c86bf1 upstream. At the moment running osnoise on a nohz_full CPU or uncontested FIFO priority and a PREEMPT_RCU kernel might have the side effect of extending grace periods too much. This will entice RCU to force a context switch on the wayward CPU to end the grace period, all while introducing unwarranted noise into the tracer. This behaviour is unavoidable as overly extending grace periods might exhaust the system's memory. This same exact problem is what extended quiescent states (EQS) were created for, conversely, rcu_momentary_dyntick_idle() emulates them by performing a zero duration EQS. So let's make use of it. In the common case rcu_momentary_dyntick_idle() is fairly inexpensive: atomically incrementing a local per-CPU counter and doing a store. So it shouldn't affect osnoise's measurements (which has a 1us granularity), so we'll call it unanimously. The uncommon case involve calling rcu_momentary_dyntick_idle() after having the osnoise process: - Receive an expedited quiescent state IPI with preemption disabled or during an RCU critical section. (activates rdp->cpu_no_qs.b.exp code-path). - Being preempted within in an RCU critical section and having the subsequent outermost rcu_read_unlock() called with interrupts disabled. (t->rcu_read_unlock_special.b.blocked code-path). Neither of those are possible at the moment, and are unlikely to be in the future given the osnoise's loop design. On top of this, the noise generated by the situations described above is unavoidable, and if not exposed by rcu_momentary_dyntick_idle() will be eventually seen in subsequent rcu_read_unlock() calls or schedule operations. Link: https://lkml.kernel.org/r/20220307180740.577607-1-nsaenzju@redhat.com Cc: stable@vger.kernel.org Fixes: bce29ac9ce ("trace: Add osnoise tracer") Signed-off-by: Nicolas Saenz Julienne <nsaenzju@redhat.com> Acked-by: Paul E. McKenney <paulmck@kernel.org> Acked-by: Daniel Bristot de Oliveira <bristot@kernel.org> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>		2022-03-16 14:23:43 +01:00
..
bpf	bpf: Fix possible race in inc_misses_counter	2022-03-08 19:12:40 +01:00
cgroup	cgroup-v1: Correct privileges check in release_agent writes	2022-03-02 11:47:47 +01:00
configs	drivers/char: remove /dev/kmem for good	2021-05-07 00:26:34 -07:00
debug	kdb: Adopt scheduler's task classification	2021-11-18 19:17:06 +01:00
dma	swiotlb: fix info leak with DMA_FROM_DEVICE	2022-03-16 14:23:40 +01:00
entry	signal: Replace force_fatal_sig with force_exit_sig when in doubt	2021-11-25 09:49:07 +01:00
events	perf: Fix list corruption in perf_cgroup_switch()	2022-02-16 12:56:41 +01:00
gcov	Kconfig: Introduce ARCH_WANTS_NO_INSTR and CC_HAS_NO_PROFILE_FN_ATTR	2021-06-22 11:07:18 -07:00
irq	PCI/MSI: Move non-mask check back into low level accessors	2021-11-18 19:17:14 +01:00
kcsan	LKMM updates:	2021-09-02 13:00:15 -07:00
livepatch	livepatch: Replace deprecated CPU-hotplug functions.	2021-08-19 12:00:24 +02:00
locking	lockdep: Correct lock_classes index mapping	2022-02-23 12:03:22 +01:00
power	PM: s2idle: ACPI: Fix wakeup interrupts handling	2022-02-16 12:56:19 +01:00
printk	printk: restore flushing of NMI buffers on remote CPUs after NMI backtraces	2021-11-25 09:48:45 +01:00
rcu	rcu: Tighten rcu_advance_cbs_nowake() checks	2022-01-29 10:58:25 +01:00
sched	sched: Fix yet more sched_fork() races	2022-03-08 19:12:49 +01:00
time	clocksource: Avoid accidental unstable marking of clocksources	2022-01-27 11:04:08 +01:00
trace	tracing/osnoise: Force quiescent states while tracing	2022-03-16 14:23:43 +01:00
.gitignore	.gitignore: prefix local generated files with a slash	2021-05-02 00:43:35 +09:00
acct.c	kernel/acct.c: use dedicated helper to access rlimit values	2021-09-08 11:50:26 -07:00
async.c	Revert "module, async: async_synchronize_full() on module init iff async is used"	2022-02-23 12:03:07 +01:00
audit_fsnotify.c
audit_tree.c	audit: move put_tree() to avoid trim_trees refcount underflow and UAF	2021-08-24 18:52:36 -04:00
audit_watch.c
audit.c	audit: improve audit queue handling when "audit=1" on cmdline	2022-02-08 18:34:03 +01:00
audit.h	audit: add header protection to kernel/audit.h	2021-07-19 22:38:24 -04:00
auditfilter.c	lsm: separate security_task_getsecid() into subjective and objective variants	2021-03-22 15:23:32 -04:00
auditsc.c	audit: fix possible null-pointer dereference in audit_filter_rules	2021-10-18 18:27:47 -04:00
backtracetest.c
bounds.c
capability.c
cfi.c	cfi: Use rcu_read_{un}lock_sched_notrace	2021-08-11 13:11:12 -07:00
compat.c	arch: remove compat_alloc_user_space	2021-09-08 15:32:35 -07:00
configs.c
context_tracking.c
cpu_pm.c	PM: cpu: Make notifier chain use a raw_spinlock_t	2021-08-16 18:55:32 +02:00
cpu.c	sched/scs: Reset task stack state in bringup_cpu()	2021-12-01 09:04:54 +01:00
crash_core.c	kernel/crash_core: suppress unknown crashkernel parameter warning	2021-12-29 12:28:49 +01:00
crash_dump.c
cred.c	ucounts: Base set_cred_ucounts changes on the real user	2022-02-23 12:03:20 +01:00
delayacct.c	delayacct: Add sysctl to enable at runtime	2021-05-12 11:43:25 +02:00
dma.c
exec_domain.c
exit.c	io_uring: remove files pointer in cancellation functions	2021-08-23 13:10:37 -06:00
extable.c
fail_function.c
fork.c	sched: Fix yet more sched_fork() races	2022-03-08 19:12:49 +01:00
freezer.c	sched: Add get_current_state()	2021-06-18 11:43:08 +02:00
futex.c	futex: Remove unused variable 'vpid' in futex_proxy_trylock_atomic()	2021-09-03 23:00:22 +02:00
gen_kheaders.sh	kbuild: clean up ${quiet} checks in shell scripts	2021-05-27 04:01:50 +09:00
groups.c
hung_task.c	Merge branch 'akpm' (patches from Andrew)	2021-07-02 12:08:10 -07:00
iomem.c
irq_work.c	irq_work: Make irq_work_queue() NMI-safe again	2021-06-10 10:00:08 +02:00
jump_label.c	jump_label: Fix jump_label_text_reserved() vs __init	2021-07-05 10:46:20 +02:00
kallsyms.c	module: add printk formats to add module build ID to stacktraces	2021-07-08 11:48:22 -07:00
kcmp.c
Kconfig.freezer
Kconfig.hz
Kconfig.locks	locking/rwlock: Provide RT variant	2021-08-17 17:50:51 +02:00
Kconfig.preempt	sched/core: Disable CONFIG_SCHED_CORE by default	2021-06-28 22:43:05 +02:00
kcov.c
kexec_core.c	Merge branch 'rework/printk_safe-removal' into for-linus	2021-08-30 16:36:10 +02:00
kexec_elf.c
kexec_file.c	kernel: kexec_file: fix error return code of kexec_calculate_store_digests()	2021-05-07 00:26:32 -07:00
kexec_internal.h
kexec.c	kexec: avoid compat_alloc_user_space	2021-09-08 15:32:34 -07:00
kheaders.c
kmod.c	modules: add CONFIG_MODPROBE_PATH	2021-05-07 00:26:33 -07:00
kprobes.c	kprobes: Limit max data_size of the kretprobe instances	2021-12-08 09:04:41 +01:00
ksysfs.c
kthread.c	Merge branch 'akpm' (patches from Andrew)	2021-06-29 17:29:11 -07:00
latencytop.c
Makefile	kbuild: update config_data.gz only when the content of .config is changed	2021-05-02 00:43:35 +09:00
module_signature.c
module_signing.c
module-internal.h
module.c	Revert "module, async: async_synchronize_full() on module init iff async is used"	2022-02-23 12:03:07 +01:00
notifier.c	notifier: Remove atomic_notifier_call_chain_robust()	2021-08-16 18:55:32 +02:00
nsproxy.c	memcg: enable accounting for new namesapces and struct nsproxy	2021-09-03 09:58:12 -07:00
padata.c	padata: Remove repeated verbose license text	2021-08-27 16:30:18 +08:00
panic.c	Merge branch 'rework/printk_safe-removal' into for-linus	2021-08-30 16:36:10 +02:00
params.c	params: lift param_set_uint_minmax to common code	2021-08-16 14:42:22 +02:00
pid_namespace.c	memcg: enable accounting for new namesapces and struct nsproxy	2021-09-03 09:58:12 -07:00
pid.c	kernel/pid.c: implement additional checks upon pidfd_create() parameters	2021-08-10 12:53:07 +02:00
profile.c	profiling: fix shift-out-of-bounds bugs	2021-09-08 11:50:26 -07:00
ptrace.c	sched: Change task_struct::state	2021-06-18 11:43:09 +02:00
range.c
reboot.c	reboot: Add hardware protection power-off	2021-06-21 13:08:36 +01:00
regset.c
relay.c
resource_kunit.c
resource.c	kernel/resource: fix return code check in __request_free_mem_region	2021-05-14 19:41:32 -07:00
rseq.c	KVM: rseq: Update rseq when processing NOTIFY_RESUME on xfer to KVM guest	2021-09-22 10:24:01 -04:00
scftorture.c	scftorture: Avoid NULL pointer exception on early exit	2021-07-27 11:39:30 -07:00
scs.c	scs: Release kasan vmalloc poison in scs_free process	2021-11-18 19:16:29 +01:00
seccomp.c	seccomp: Invalidate seccomp mode to catch death failures	2022-02-16 12:56:38 +01:00
signal.c	signal: In get_signal test for signal_group_exit every time through the loop	2022-03-08 19:12:34 +01:00
smp.c	smp: Fix all kernel-doc warnings	2021-08-11 14:47:16 +02:00
smpboot.c	smpboot: Replace deprecated CPU-hotplug functions.	2021-08-10 14:57:42 +02:00
smpboot.h
softirq.c	genirq: Change force_irqthreads to a static key	2021-08-10 22:50:07 +02:00
stackleak.c	gcc-plugins/stackleak: Use noinstr in favor of notrace	2022-02-23 12:03:07 +01:00
stacktrace.c
static_call.c	static_call: Fix static_call_text_reserved() vs __init	2021-07-05 10:46:33 +02:00
stop_machine.c	stop_machine: Add caller debug info to queue_stop_cpus_work	2021-03-23 16:01:58 +01:00
sys_ni.c	compat: remove some compat entry points	2021-09-08 15:32:35 -07:00
sys.c	ucounts: Move RLIMIT_NPROC handling after set_user	2022-02-23 12:03:20 +01:00
sysctl-test.c	kernel/sysctl-test: Remove some casts which are no-longer required	2021-06-23 16:41:24 -06:00
sysctl.c	x86/speculation: Include unprivileged eBPF status in Spectre v2 mitigation reporting	2022-03-11 12:22:31 +01:00
task_work.c	kasan: record task_work_add() call stack	2021-04-30 11:20:42 -07:00
taskstats.c
test_kprobes.c
torture.c	torture: Replace deprecated CPU-hotplug functions.	2021-08-10 10:48:07 -07:00
tracepoint.c	tracepoint: Fix kerneldoc comments	2021-08-16 11:39:51 -04:00
tsacct.c	taskstats: Cleanup the use of task->exit_code	2022-01-27 11:05:35 +01:00
ucount.c	ucounts: Handle wrapping in is_ucounts_overlimit	2022-02-23 12:03:20 +01:00
uid16.c
uid16.h
umh.c	kernel/umh.c: fix some spelling mistakes	2021-05-07 00:26:34 -07:00
up.c	A set of locking related fixes and updates:	2021-05-09 13:07:03 -07:00
user_namespace.c	ucounts: Fix systemd LimitNPROC with private users regression	2022-03-08 19:12:42 +01:00
user-return-notifier.c
user.c	fs/epoll: use a per-cpu counter for user's watches count	2021-09-08 11:50:27 -07:00
usermode_driver.c	Merge branch 'work.namei' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs	2021-07-03 11:41:14 -07:00
utsname_sysctl.c
utsname.c
watch_queue.c
watchdog_hld.c
watchdog.c	kernel: watchdog: modify the explanation related to watchdog thread	2021-06-29 10:53:46 -07:00
workqueue_internal.h	workqueue: Assign a color to barrier work items	2021-08-17 07:49:10 -10:00
workqueue.c	workqueue: Fix unbind_workers() VS wq_worker_running() race	2022-01-16 09:12:41 +01:00