From: Peter Zijlstra <peterz@infradead.org>
To: Kirill Tkhai <tkhai@yandex.ru>
Cc: Oleg Nesterov <oleg@redhat.com>,
Kautuk Consul <consul.kautuk@gmail.com>,
Ingo Molnar <mingo@redhat.com>,
Andrew Morton <akpm@linux-foundation.org>,
Michal Hocko <mhocko@suse.cz>,
David Rientjes <rientjes@google.com>,
Ionut Alexa <ionut.m.alexa@gmail.com>,
Guillaume Morin <guillaume@morinfr.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 1/1] do_exit(): Solve possibility of BUG() due to race with try_to_wake_up()
Date: Wed, 3 Sep 2014 11:45:38 +0200 [thread overview]
Message-ID: <20140903094538.GF4783@worktop.ger.corp.intel.com> (raw)
In-Reply-To: <3702911409735076@web26g.yandex.ru>
On Wed, Sep 03, 2014 at 01:04:36PM +0400, Kirill Tkhai wrote:
> 25.08.2014, 20:01, "Oleg Nesterov" <oleg@redhat.com>:
> > Peter, do you remember another problem with TASK_DEAD we discussed recently?
> > (prev_state == TASK_DEAD detection in finish_task_switch() still looks racy).
>
> One more problem with task_dead just to mention it here.
>
> Below is racy with the change of sched_class:
>
> if (prev->sched_class->task_dead)
> prev->sched_class->task_dead(prev);
>
> switched_from_dl() does not cancel running timers.
Well, it does a try_to_cancel() but yes, that can fail. Now I suspect
you cannot actually do hrtimer_cancel() from switched_from because its
called with locks held and the timer function will also try and acquire
those locks.
But yes, that appears to be an actual problem indeed.
prev parent reply other threads:[~2014-09-03 9:45 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-08-25 10:54 [PATCH 1/1] do_exit(): Solve possibility of BUG() due to race with try_to_wake_up() Kautuk Consul
2014-08-25 15:57 ` Oleg Nesterov
2014-08-26 4:45 ` Kautuk Consul
2014-08-26 15:03 ` Oleg Nesterov
2014-09-01 15:39 ` Peter Zijlstra
2014-09-01 17:58 ` Oleg Nesterov
2014-09-01 19:09 ` Peter Zijlstra
2014-09-02 15:52 ` Oleg Nesterov
2014-09-02 16:47 ` Oleg Nesterov
2014-09-02 17:39 ` Peter Zijlstra
2014-09-03 13:36 ` Oleg Nesterov
2014-09-03 14:44 ` Peter Zijlstra
2014-09-03 15:18 ` Oleg Nesterov
2014-09-04 7:15 ` Peter Zijlstra
2014-09-04 17:03 ` Paul E. McKenney
2014-09-04 5:04 ` Ingo Molnar
2014-09-04 6:32 ` Peter Zijlstra
2014-09-03 16:08 ` task_numa_fault() && TASK_DEAD Oleg Nesterov
2014-09-03 16:33 ` Rik van Riel
2014-09-04 7:11 ` Peter Zijlstra
2014-09-04 10:39 ` Oleg Nesterov
2014-09-04 19:14 ` Hugh Dickins
2014-09-05 11:35 ` Oleg Nesterov
2014-09-03 9:04 ` [PATCH 1/1] do_exit(): Solve possibility of BUG() due to race with try_to_wake_up() Kirill Tkhai
2014-09-03 9:45 ` Peter Zijlstra [this message]
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