From: Oleg Nesterov <oleg@redhat.com>
To: Michal Hocko <mhocko@suse.cz>
Cc: David Rientjes <rientjes@google.com>,
Andrew Morton <akpm@linux-foundation.org>,
Konstantin Khlebnikov <khlebnikov@openvz.org>,
KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>,
KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
"Rafael J. Wysocki" <rjw@sisk.pl>,
Rusty Russell <rusty@rustcorp.com.au>,
Tejun Heo <htejun@gmail.com>,
linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [patch] oom: thaw threads if oom killed thread is frozen before deferring
Date: Thu, 29 Sep 2011 14:05:17 +0200 [thread overview]
Message-ID: <20110929120517.GA10587@redhat.com> (raw)
In-Reply-To: <20110929115105.GE21113@tiehlicka.suse.cz>
On 09/29, Michal Hocko wrote:
>
> --- a/kernel/freezer.c
> +++ b/kernel/freezer.c
> @@ -48,6 +48,10 @@ void refrigerator(void)
> current->flags |= PF_FREEZING;
>
> for (;;) {
> + if (fatal_signal_pending(current)) {
> + current->flags &= ~PF_FROZEN;
We can't do this.
If PF_FROZEN was set, we must not modify current->flags, this can
race with, say, thaw_process().
OK, we can take task_lock(), but this doesn't close other races.
Say, a SIGKILL'ed task can do try_to_freeze(). Perhaps we should
simply call thaw_process() unconditionally, this also clears
TIF_FREEZE. Or check freezing() || frozen(). Afacis this solves
the race you described.
But of course this can't help if freeze_task() is called later.
May be freezable() should check TIF_MEMDIE...
Oleg.
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next prev parent reply other threads:[~2011-09-29 12:09 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-09-27 8:09 [PATCH 0/2] oom: fix livelock when frozen task is selected Michal Hocko
2011-09-27 6:56 ` [PATCH 1/2] lguest: move process freezing before pending signals check Michal Hocko
2011-10-12 6:55 ` Michal Hocko
2011-10-12 23:57 ` Rusty Russell
2011-10-13 5:48 ` Michal Hocko
2011-09-27 8:01 ` [PATCH 2/2] oom: do not live lock on frozen tasks Michal Hocko
2011-09-27 18:35 ` [patch] oom: thaw threads if oom killed thread is frozen before deferring David Rientjes
2011-09-28 10:44 ` Michal Hocko
2011-09-29 11:51 ` Michal Hocko
2011-09-29 12:05 ` Oleg Nesterov [this message]
2011-09-29 13:02 ` Michal Hocko
2011-09-29 16:32 ` Michal Hocko
2011-09-29 16:37 ` Oleg Nesterov
2011-09-29 18:00 ` Michal Hocko
2011-09-30 1:51 ` Tejun Heo
2011-09-30 7:41 ` Michal Hocko
2011-09-30 7:46 ` Tejun Heo
2011-09-30 8:04 ` Michal Hocko
2011-09-30 15:30 ` Oleg Nesterov
2011-10-28 22:23 ` [PATCH 2/2] oom: do not live lock on frozen tasks Andrew Morton
2011-10-29 9:01 ` Michal Hocko
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