From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754031Ab3KIPPc (ORCPT ); Sat, 9 Nov 2013 10:15:32 -0500 Received: from mx1.redhat.com ([209.132.183.28]:5378 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753275Ab3KIPPb (ORCPT ); Sat, 9 Nov 2013 10:15:31 -0500 Date: Sat, 9 Nov 2013 16:16:39 +0100 From: Oleg Nesterov To: Sameer Nanda Cc: akpm@linux-foundation.org, mhocko@suse.cz, rientjes@google.com, hannes@cmpxchg.org, rusty@rustcorp.com.au, semenzato@google.com, murzin.v@gmail.com, dserrg@gmail.com, msb@chromium.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v3] mm, oom: Fix race when selecting process to kill Message-ID: <20131109151639.GB14249@redhat.com> References: <20131108184515.GA11555@redhat.com> <1383940173-16480-1-git-send-email-snanda@chromium.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1383940173-16480-1-git-send-email-snanda@chromium.org> User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 11/08, Sameer Nanda wrote: > > @@ -413,12 +413,20 @@ void oom_kill_process(struct task_struct *p, gfp_t gfp_mask, int order, > DEFAULT_RATELIMIT_BURST); > @@ -456,10 +463,18 @@ void oom_kill_process(struct task_struct *p, gfp_t gfp_mask, int order, > } > } > } while_each_thread(p, t); > - read_unlock(&tasklist_lock); > > rcu_read_lock(); > + > p = find_lock_task_mm(victim); > + > + /* > + * Since while_each_thread is currently not RCU safe, this unlock of > + * tasklist_lock may need to be moved further down if any additional > + * while_each_thread loops get added to this function. > + */ > + read_unlock(&tasklist_lock); Well, ack... but with this change find_lock_task_mm() relies on tasklist, so it makes sense to move rcu_read_lock() down before for_each_process(). Otherwise this looks confusing, but I won't insist. Oleg.