From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-bk0-f51.google.com (mail-bk0-f51.google.com [209.85.214.51]) by kanga.kvack.org (Postfix) with ESMTP id 463466B0035 for ; Thu, 28 Nov 2013 01:35:24 -0500 (EST) Received: by mail-bk0-f51.google.com with SMTP id 6so3547913bkj.24 for ; Wed, 27 Nov 2013 22:35:23 -0800 (PST) Received: from zene.cmpxchg.org (zene.cmpxchg.org. [2a01:238:4224:fa00:ca1f:9ef3:caee:a2bd]) by mx.google.com with ESMTPS id lf2si13154010bkb.218.2013.11.27.22.35.22 for (version=TLSv1 cipher=RC4-SHA bits=128/128); Wed, 27 Nov 2013 22:35:22 -0800 (PST) Date: Thu, 28 Nov 2013 01:35:05 -0500 From: Johannes Weiner Subject: Re: [PATCH] Fix race between oom kill and task exit Message-ID: <20131128063505.GN3556@cmpxchg.org> References: <3917C05D9F83184EAA45CE249FF1B1DD0253093A@SHSMSX103.ccr.corp.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <3917C05D9F83184EAA45CE249FF1B1DD0253093A@SHSMSX103.ccr.corp.intel.com> Sender: owner-linux-mm@kvack.org List-ID: To: "Ma, Xindong" Cc: "akpm@linux-foundation.org" , "mhocko@suse.cz" , "rientjes@google.com" , "rusty@rustcorp.com.au" , "linux-mm@kvack.org" , "linux-kernel@vger.kernel.org" , 'Peter Zijlstra' , "'gregkh@linuxfoundation.org'" , "Tu, Xiaobing" , William Dauchy , azurIt Cc William and azur who might have encountered this problem. On Thu, Nov 28, 2013 at 05:09:16AM +0000, Ma, Xindong wrote: > From: Leon Ma > Date: Thu, 28 Nov 2013 12:46:09 +0800 > Subject: [PATCH] Fix race between oom kill and task exit > > There is a race between oom kill and task exit. Scenario is: > TASK A TASK B > TASK B is selected to oom kill > in oom_kill_process() > check PF_EXITING of TASK B > task call do_exit() > task set PF_EXITING flag > write_lock_irq(&tasklist_lock); > remove TASK B from thread group in __unhash_process() > write_unlock_irq(&tasklist_lock); > read_lock(&tasklist_lock); > traverse threads of TASK B > read_unlock(&tasklist_lock); > > After that, the following traversal of threads in TASK B will not end because TASK B is not in the thread group: > do { > .... > } while_each_thread(p, t); > > Signed-off-by: Leon Ma > Signed-off-by: xiaobing tu > --- > mm/oom_kill.c | 20 ++++++++++---------- > 1 files changed, 10 insertions(+), 10 deletions(-) > > diff --git a/mm/oom_kill.c b/mm/oom_kill.c > index 1e4a600..32ec88d 100644 > --- a/mm/oom_kill.c > +++ b/mm/oom_kill.c > @@ -412,16 +412,6 @@ void oom_kill_process(struct task_struct *p, gfp_t gfp_mask, int order, > static DEFINE_RATELIMIT_STATE(oom_rs, DEFAULT_RATELIMIT_INTERVAL, > DEFAULT_RATELIMIT_BURST); > > - /* > - * If the task is already exiting, don't alarm the sysadmin or kill > - * its children or threads, just set TIF_MEMDIE so it can die quickly > - */ > - if (p->flags & PF_EXITING) { > - set_tsk_thread_flag(p, TIF_MEMDIE); > - put_task_struct(p); > - return; > - } > - > if (__ratelimit(&oom_rs)) > dump_header(p, gfp_mask, order, memcg, nodemask); > > @@ -437,6 +427,16 @@ void oom_kill_process(struct task_struct *p, gfp_t gfp_mask, int order, > * still freeing memory. > */ > read_lock(&tasklist_lock); > + /* > + * If the task is already exiting, don't alarm the sysadmin or kill > + * its children or threads, just set TIF_MEMDIE so it can die quickly > + */ > + if (p->flags & PF_EXITING) { > + set_tsk_thread_flag(p, TIF_MEMDIE); > + put_task_struct(p); > + read_unlock(&tasklist_lock); > + return; > + } > do { > list_for_each_entry(child, &t->children, sibling) { > unsigned int child_points; > -- > 1.7.4.1 > -- 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