From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail138.messagelabs.com (mail138.messagelabs.com [216.82.249.35]) by kanga.kvack.org (Postfix) with SMTP id 6D9BE9000BD for ; Thu, 29 Sep 2011 08:09:01 -0400 (EDT) Date: Thu, 29 Sep 2011 14:05:17 +0200 From: Oleg Nesterov Subject: Re: [patch] oom: thaw threads if oom killed thread is frozen before deferring Message-ID: <20110929120517.GA10587@redhat.com> References: <65d9dff7ff78fad1f146e71d32f9f92741281b46.1317110948.git.mhocko@suse.cz> <20110928104445.GB15062@tiehlicka.suse.cz> <20110929115105.GE21113@tiehlicka.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20110929115105.GE21113@tiehlicka.suse.cz> Sender: owner-linux-mm@kvack.org List-ID: To: Michal Hocko Cc: David Rientjes , Andrew Morton , Konstantin Khlebnikov , KOSAKI Motohiro , KAMEZAWA Hiroyuki , "Rafael J. Wysocki" , Rusty Russell , Tejun Heo , linux-kernel@vger.kernel.org, linux-mm@kvack.org 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. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org