From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail203.messagelabs.com (mail203.messagelabs.com [216.82.254.243]) by kanga.kvack.org (Postfix) with ESMTP id 98CC5900194 for ; Wed, 22 Jun 2011 19:01:52 -0400 (EDT) Received: from hpaq14.eem.corp.google.com (hpaq14.eem.corp.google.com [172.25.149.14]) by smtp-out.google.com with ESMTP id p5MN1iZg018438 for ; Wed, 22 Jun 2011 16:01:44 -0700 Received: from pve37 (pve37.prod.google.com [10.241.210.37]) by hpaq14.eem.corp.google.com with ESMTP id p5MN1HKN025939 (version=TLSv1/SSLv3 cipher=RC4-SHA bits=128 verify=NOT) for ; Wed, 22 Jun 2011 16:01:42 -0700 Received: by pve37 with SMTP id 37so1113143pve.21 for ; Wed, 22 Jun 2011 16:01:37 -0700 (PDT) Date: Wed, 22 Jun 2011 16:01:35 -0700 (PDT) From: David Rientjes Subject: Re: [PATCH 3/6] oom: kill younger process first In-Reply-To: <4E01C84A.60400@jp.fujitsu.com> Message-ID: References: <4E01C7D5.3060603@jp.fujitsu.com> <4E01C84A.60400@jp.fujitsu.com> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org List-ID: To: KOSAKI Motohiro Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Andrew Morton , caiqian@redhat.com, Hugh Dickins , KAMEZAWA Hiroyuki , Minchan Kim , Oleg Nesterov On Wed, 22 Jun 2011, KOSAKI Motohiro wrote: > diff --git a/include/linux/sched.h b/include/linux/sched.h > index e4e6d7b..392ff30 100644 > --- a/include/linux/sched.h > +++ b/include/linux/sched.h > @@ -2257,6 +2257,9 @@ static inline unsigned long wait_task_inactive(struct task_struct *p, > #define next_task(p) \ > list_entry_rcu((p)->tasks.next, struct task_struct, tasks) > > +#define prev_task(p) \ > + list_entry((p)->tasks.prev, struct task_struct, tasks) > + > #define for_each_process(p) \ > for (p = &init_task ; (p = next_task(p)) != &init_task ; ) > > @@ -2269,6 +2272,14 @@ extern bool current_is_single_threaded(void); > #define do_each_thread(g, t) \ > for (g = t = &init_task ; (g = t = next_task(g)) != &init_task ; ) do > > +/* > + * Similar to do_each_thread(). but two difference are there. > + * - traverse tasks reverse order (i.e. younger to older) > + * - caller must hold tasklist_lock. rcu_read_lock isn't enough > +*/ > +#define do_each_thread_reverse(g, t) \ > + for (g = t = &init_task ; (g = t = prev_task(g)) != &init_task ; ) do > + > #define while_each_thread(g, t) \ > while ((t = next_thread(t)) != g) > I've already ack'd the patch, but if there is another version posted as a result of our discussion of using euid in the heuristic, I think it would be helpful to reiterate in this comment that, like do_each_thread(), do_each_thread_reverse() is not break-safe either. It might end up preventing a bug down the road. -- 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