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posix-cpu-timers: Force next_expiration recalc after timer deletion

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A timer deletion only dequeues the timer but it doesn't shutdown
the related costly process wide cputimer counter and the tick dependency.

The following code snippet keeps this overhead around for one week after
the timer deletion:

	void trigger_process_counter(void)
	{
		timer_t id;
		struct itimerspec val = { };

		val.it_value.tv_sec = 604800;
		timer_create(CLOCK_PROCESS_CPUTIME_ID, NULL, &id);
		timer_settime(id, 0, &val, NULL);
		timer_delete(id);
	}

Make sure the next target's tick recalculates the nearest expiration and
clears the process wide counter and tick dependency if necessary.

Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20210726125513.271824-3-frederic@kernel.org
This commit is contained in:
Frederic Weisbecker
2021-07-26 14:55:09 +02:00
committed by Thomas Gleixner
parent a5dec9f82a
commit 175cc3ab28
2 changed files with 35 additions and 2 deletions
Download Patch File Download Diff File Expand all files Collapse all files

4
include/linux/posix-timers.h
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@@ -82,12 +82,14 @@ static inline bool cpu_timer_enqueue(struct timerqueue_head *head,
return timerqueue_add(head, &ctmr->node);
}
static inline void cpu_timer_dequeue(struct cpu_timer *ctmr)
static inline bool cpu_timer_dequeue(struct cpu_timer *ctmr)
{
if (ctmr->head) {
timerqueue_del(ctmr->head, &ctmr->node);
ctmr->head = NULL;
return true;
}
return false;
}
static inline u64 cpu_timer_getexpires(struct cpu_timer *ctmr)