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Commit a11ce3a4 authored by Linus Torvalds's avatar Linus Torvalds
Browse files

Merge branch 'timers-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 

Pull NOHZ fix from Ingo Molnar:
 "This fixes an old NOHZ race where we incorrectly calculate the next
  timer interrupt in certain circumstances where hrtimers are pending,
  that can cause hard to reproduce stalled-values artifacts in
  /proc/stat"

* 'timers-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  nohz: Fix collision between tick and other hrtimers
parents 79078c53 24b91e36

kernel/time/tick-sched.c

+7 −2
Original line number Diff line number Diff line
@@ -767,7 +767,7 @@ static ktime_t tick_nohz_stop_sched_tick(struct tick_sched *ts, 
	tick = expires;



	/* Skip reprogram of event if its not changed */

	if (ts->tick_stopped && (expires == dev->next_event))

	if (ts->tick_stopped && (expires == ts->next_tick))

		goto out;



	/*
@@ -787,6 +787,8 @@ static ktime_t tick_nohz_stop_sched_tick(struct tick_sched *ts, 
		trace_tick_stop(1, TICK_DEP_MASK_NONE);

	}



	ts->next_tick = tick;



	/*

	 * If the expiration time == KTIME_MAX, then we simply stop

	 * the tick timer.
@@ -802,7 +804,10 @@ static ktime_t tick_nohz_stop_sched_tick(struct tick_sched *ts, 
	else

		tick_program_event(tick, 1);

out:

	/* Update the estimated sleep length */

	/*

	 * Update the estimated sleep length until the next timer

	 * (not only the tick).

	 */

	ts->sleep_length = ktime_sub(dev->next_event, now);

	return tick;

}

kernel/time/tick-sched.h

+2 −0
Original line number Diff line number Diff line
@@ -27,6 +27,7 @@ enum tick_nohz_mode { 
 *			timer is modified for nohz sleeps. This is necessary

 *			to resume the tick timer operation in the timeline

 *			when the CPU returns from nohz sleep.

 * @next_tick:		Next tick to be fired when in dynticks mode.

 * @tick_stopped:	Indicator that the idle tick has been stopped

 * @idle_jiffies:	jiffies at the entry to idle for idle time accounting

 * @idle_calls:		Total number of idle calls
@@ -44,6 +45,7 @@ struct tick_sched { 
	unsigned long			check_clocks;

	enum tick_nohz_mode		nohz_mode;

	ktime_t				last_tick;

	ktime_t				next_tick;

	int				inidle;

	int				tick_stopped;

	unsigned long			idle_jiffies;