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 56DE66B0012 for ; Mon, 23 May 2011 18:21:15 -0400 (EDT) Received: from wpaz29.hot.corp.google.com (wpaz29.hot.corp.google.com [172.24.198.93]) by smtp-out.google.com with ESMTP id p4NML2hg029837 for ; Mon, 23 May 2011 15:21:04 -0700 Received: from pve37 (pve37.prod.google.com [10.241.210.37]) by wpaz29.hot.corp.google.com with ESMTP id p4NMKbX1031965 (version=TLSv1/SSLv3 cipher=RC4-SHA bits=128 verify=NOT) for ; Mon, 23 May 2011 15:20:56 -0700 Received: by pve37 with SMTP id 37so3950291pve.35 for ; Mon, 23 May 2011 15:20:56 -0700 (PDT) Date: Mon, 23 May 2011 15:20:54 -0700 (PDT) From: David Rientjes Subject: Re: [PATCH 2/5] oom: kill younger process first In-Reply-To: <4DD62007.6020600@jp.fujitsu.com> Message-ID: References: <4DD61F80.1020505@jp.fujitsu.com> <4DD62007.6020600@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, akpm@linux-foundation.org, caiqian@redhat.com, hughd@google.com, kamezawa.hiroyu@jp.fujitsu.com, minchan.kim@gmail.com, oleg@redhat.com On Fri, 20 May 2011, KOSAKI Motohiro wrote: > diff --git a/include/linux/sched.h b/include/linux/sched.h > index 013314a..3698379 100644 > --- a/include/linux/sched.h > +++ b/include/linux/sched.h > @@ -2194,6 +2194,9 @@ 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 ; ) > > @@ -2206,6 +2209,14 @@ 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) > > diff --git a/mm/oom_kill.c b/mm/oom_kill.c > index 43d32ae..e6a6c6f 100644 > --- a/mm/oom_kill.c > +++ b/mm/oom_kill.c > @@ -282,7 +282,7 @@ static struct task_struct *select_bad_process(unsigned int *ppoints, > struct task_struct *chosen = NULL; > *ppoints = 0; > > - do_each_thread(g, p) { > + do_each_thread_reverse(g, p) { > unsigned int points; > > if (!p->mm) Same response as when you initially proposed this patch: the comment needs to explicitly state that it is not break-safe just like do_each_thread(). See http://marc.info/?l=linux-mm&m=130507027312785 A comment such as /* * Reverse of do_each_thread(); still not break-safe. * Must hold tasklist_lock. */ would suffice. There are no "callers" to a macro. After that: Acked-by: David Rientjes -- 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