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| author | Thomas Gleixner <tglx@linutronix.de> | 2023-04-25 20:49:00 +0200 |
|---|---|---|
| committer | Thomas Gleixner <tglx@linutronix.de> | 2023-06-18 22:41:48 +0200 |
| commit | 7d9909026645064cd31b20cee5939a0f72282261 (patch) | |
| tree | 9440111cc1638de03565083ff20ad670691dcfc7 /kernel/time | |
| parent | 8ce8849dd1e78dadcee0ec9acbd259d239b7069f (diff) | |
| download | linux-7d9909026645064cd31b20cee5939a0f72282261.tar.gz | |
posix-timers: Clarify timer_wait_running() comment
Explain it better and add the CONFIG_POSIX_CPU_TIMERS_TASK_WORK=y aspect
for completeness.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Link: https://lore.kernel.org/r/20230425183312.985681995@linutronix.de
Diffstat (limited to 'kernel/time')
| -rw-r--r-- | kernel/time/posix-timers.c | 16 |
1 files changed, 12 insertions, 4 deletions
diff --git a/kernel/time/posix-timers.c b/kernel/time/posix-timers.c index 2d6cf93ca370a..0c61f29ef5d51 100644 --- a/kernel/time/posix-timers.c +++ b/kernel/time/posix-timers.c @@ -836,10 +836,18 @@ static void common_timer_wait_running(struct k_itimer *timer) } /* - * On PREEMPT_RT this prevent priority inversion against softirq kthread in - * case it gets preempted while executing a timer callback. See comments in - * hrtimer_cancel_wait_running. For PREEMPT_RT=n this just results in a - * cpu_relax(). + * On PREEMPT_RT this prevents priority inversion and a potential livelock + * against the ksoftirqd thread in case that ksoftirqd gets preempted while + * executing a hrtimer callback. + * + * See the comments in hrtimer_cancel_wait_running(). For PREEMPT_RT=n this + * just results in a cpu_relax(). + * + * For POSIX CPU timers with CONFIG_POSIX_CPU_TIMERS_TASK_WORK=n this is + * just a cpu_relax(). With CONFIG_POSIX_CPU_TIMERS_TASK_WORK=y this + * prevents spinning on an eventually scheduled out task and a livelock + * when the task which tries to delete or disarm the timer has preempted + * the task which runs the expiry in task work context. */ static struct k_itimer *timer_wait_running(struct k_itimer *timer, unsigned long *flags) |