On 06/08, Peter Zijlstra wrote: > > On Mon, Jun 08, 2015 at 04:27:49PM +0200, Oleg Nesterov wrote: > > > > Most probably I missed something... I'll try to think more, but perhaps > > you see a hole immediately? > > This is something I proposed earlier; Kirill said: > > lkml.kernel.org/r/2134411433408...@web8j.yandex.ru > > Which I read like the below, imagine our timer expires periodically and > rearms itself: > > acquire > cpu_base->running = timer; > wmb > timer->state = INACTIVE; > release > [R] timer->state (== INACTIVE) > fn() > acquire > timer->state = ACTIVE > wmb > cpu_base->running = NULL > release > > [R] cpu_base->running (== NULL) > > acquire > cpu_base->running = timer; > wmb > timer->state = INACTIVE; > release > > [R] timer->state (== INACTIVE)
Damn yes. Thanks Kirill and Peter. And I swear, I swear I was thinking about this race yesterday but forgot this problem today ;) Yes it seems that we can't avoid the seq counter. But perhaps we can increment/check it once in run_hrtimer/hrtimer_inactive ... I'll try to think. Thanks! Oleg. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
