From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail143.messagelabs.com (mail143.messagelabs.com [216.82.254.35]) by kanga.kvack.org (Postfix) with ESMTP id B3C206B01EE for ; Tue, 30 Mar 2010 16:26:52 -0400 (EDT) Received: from hpaq3.eem.corp.google.com (hpaq3.eem.corp.google.com [10.3.21.3]) by smtp-out.google.com with ESMTP id o2UKQlM8023860 for ; Tue, 30 Mar 2010 22:26:47 +0200 Received: from pzk36 (pzk36.prod.google.com [10.243.19.164]) by hpaq3.eem.corp.google.com with ESMTP id o2UKQh3x029542 for ; Tue, 30 Mar 2010 22:26:46 +0200 Received: by pzk36 with SMTP id 36so2551496pzk.24 for ; Tue, 30 Mar 2010 13:26:43 -0700 (PDT) Date: Tue, 30 Mar 2010 13:26:39 -0700 (PDT) From: David Rientjes Subject: Re: [patch] oom: give current access to memory reserves if it has been killed In-Reply-To: <20100330154659.GA12416@redhat.com> Message-ID: References: <1269447905-5939-1-git-send-email-anfei.zhou@gmail.com> <20100326150805.f5853d1c.akpm@linux-foundation.org> <20100326223356.GA20833@redhat.com> <20100328145528.GA14622@desktop> <20100328162821.GA16765@redhat.com> <20100329112111.GA16971@redhat.com> <20100330154659.GA12416@redhat.com> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org To: Oleg Nesterov Cc: Andrew Morton , anfei , KOSAKI Motohiro , nishimura@mxp.nes.nec.co.jp, KAMEZAWA Hiroyuki , Mel Gorman , linux-mm@kvack.org, linux-kernel@vger.kernel.org List-ID: On Tue, 30 Mar 2010, Oleg Nesterov wrote: > > --- a/mm/oom_kill.c > > +++ b/mm/oom_kill.c > > @@ -681,6 +681,16 @@ void out_of_memory(struct zonelist *zonelist, gfp_t gfp_mask, > > } > > > > /* > > + * If current has a pending SIGKILL, then automatically select it. The > > + * goal is to allow it to allocate so that it may quickly exit and free > > + * its memory. > > + */ > > + if (fatal_signal_pending(current)) { > > + __oom_kill_task(current); > > I am worried... > > Note that __oom_kill_task() does force_sig(SIGKILL) which assumes that > ->sighand != NULL. This is not true if out_of_memory() is called after > current has already passed exit_notify(). > We have an even bigger problem if current is in the oom killer at exit_notify() since it has already detached its ->mm in exit_mm() :) > Hmm. looking at oom_kill.c... Afaics there are more problems with mt > apllications. select_bad_process() does for_each_process() which can > only see the group leaders. This is fine, but what if ->group_leader > has already exited? In this case its ->mm == NULL, and we ignore the > whole thread group. > > IOW, unless I missed something, it is very easy to hide the process > from oom-kill: > > int main() > { > pthread_create(memory_hog_func); > syscall(__NR_exit); > } > The check for !p->mm was moved in the -mm tree (and the oom killer was entirely rewritten in that tree, so I encourage you to work off of it instead) with oom-avoid-race-for-oom-killed-tasks-detaching-mm-prior-to-exit.patch to even after the check for PF_EXITING. This is set in the exit path before the ->mm is detached so if the oom killer finds an already exiting task, it will become a no-op since it should eventually free memory and avoids a needless oom kill. -- 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/ . Don't email: email@kvack.org