Commit 8edfb036 authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Thomas Gleixner
Browse files

hrtimer: Fix hrtimer_is_queued() hole 



A queued hrtimer that gets restarted (hrtimer_start*() while
hrtimer_is_queued()) will briefly appear as unqueued/inactive, even
though the timer has always been active, we just moved it.

Close this hole by preserving timer->state in
hrtimer_start_range_ns()'s remove_hrtimer() call.

Reported-by: default avatarOleg Nesterov <oleg@redhat.com>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: ktkhai@parallels.com
Cc: rostedt@goodmis.org
Cc: juri.lelli@gmail.com
Cc: pang.xunlei@linaro.org
Cc: wanpeng.li@linux.intel.com
Cc: umgwanakikbuti@gmail.com
Link: http://lkml.kernel.org/r/20150611124743.175989138@infradead.org


Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
parent c04dca02

kernel/time/hrtimer.c

+13 −10
Original line number Diff line number Diff line
@@ -889,10 +889,10 @@ static void __remove_hrtimer(struct hrtimer *timer, 
 * remove hrtimer, called with base lock held

 */

static inline int

remove_hrtimer(struct hrtimer *timer, struct hrtimer_clock_base *base)

remove_hrtimer(struct hrtimer *timer, struct hrtimer_clock_base *base, bool restart)

{

	if (hrtimer_is_queued(timer)) {

		unsigned long state;

		unsigned long state = timer->state;

		int reprogram;



		/*
@@ -906,12 +906,15 @@ remove_hrtimer(struct hrtimer *timer, struct hrtimer_clock_base *base) 
		debug_deactivate(timer);

		timer_stats_hrtimer_clear_start_info(timer);

		reprogram = base->cpu_base == this_cpu_ptr(&hrtimer_bases);



		if (!restart) {

			/*

			 * We must preserve the CALLBACK state flag here,

			 * otherwise we could move the timer base in

			 * switch_hrtimer_base.

			 */

		state = timer->state & HRTIMER_STATE_CALLBACK;

			state &= HRTIMER_STATE_CALLBACK;

		}

		__remove_hrtimer(timer, base, state, reprogram);

		return 1;

	}
@@ -936,7 +939,7 @@ void hrtimer_start_range_ns(struct hrtimer *timer, ktime_t tim, 
	base = lock_hrtimer_base(timer, &flags);



	/* Remove an active timer from the queue: */

	remove_hrtimer(timer, base);

	remove_hrtimer(timer, base, true);



	if (mode & HRTIMER_MODE_REL) {

		tim = ktime_add_safe(tim, base->get_time());
@@ -1005,7 +1008,7 @@ int hrtimer_try_to_cancel(struct hrtimer *timer) 
	base = lock_hrtimer_base(timer, &flags);



	if (!hrtimer_callback_running(timer))

		ret = remove_hrtimer(timer, base);

		ret = remove_hrtimer(timer, base, false);



	unlock_hrtimer_base(timer, &flags);

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