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timers/migration: Mark racy updates to tmigr_event::ignore field

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The tmigr_event structure's ignore field is sometimes accessed locklessly,
but the __tmigr_cpu_activate(), tmigr_cpu_new_timer(), and
__tmigr_cpu_deactivate() functions do not mark accesses to this field.

Therefore, use READ_ONCE() for the tmigr_cpu_new_timer() function's
lockless load and WRITE_ONCE() for the __tmigr_cpu_activate() and
__tmigr_cpu_deactivate() functions' stores.

KCSAN located this issue.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Link: https://patch.msgid.link/20260919002523.3133928-2-paulmck@kernel.org
This commit is contained in:
Paul E. McKenney 2026-09-18 17:25:23 -07:00 committed by Thomas Gleixner
parent 1159ad0a6a
commit bb41ece164
1 changed files with 3 additions and 3 deletions
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6
kernel/time/timer_migration.c
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@ -715,7 +715,7 @@ static void __tmigr_cpu_activate(struct tmigr_cpu *tmc)
trace_tmigr_cpu_active(tmc);
tmc->cpuevt.ignore = true;
WRITE_ONCE(tmc->cpuevt.ignore, true);
WRITE_ONCE(tmc->wakeup, KTIME_MAX);
walk_groups(&tmigr_active_up, &data, tmc);
@ -1258,7 +1258,7 @@ u64 tmigr_cpu_new_timer(u64 nextexp)
ret = READ_ONCE(tmc->wakeup);
if (nextexp != KTIME_MAX) {
if (nextexp != tmc->cpuevt.nextevt.expires ||
tmc->cpuevt.ignore) {
READ_ONCE(tmc->cpuevt.ignore)) {
ret = tmigr_new_timer(tmc, nextexp);
/*
* Make sure the reevaluation of timers in idle path
@ -1362,7 +1362,7 @@ static u64 __tmigr_cpu_deactivate(struct tmigr_cpu *tmc, u64 nextexp)
* or CPU goes offline.
*/
if (nextexp != KTIME_MAX)
tmc->cpuevt.ignore = false;
WRITE_ONCE(tmc->cpuevt.ignore, false);
walk_groups(&tmigr_inactive_up, &data, tmc);
return data.firstexp;