From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932471Ab3LDND0 (ORCPT ); Wed, 4 Dec 2013 08:03:26 -0500 Received: from mx1.redhat.com ([209.132.183.28]:3474 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932246Ab3LDNDX (ORCPT ); Wed, 4 Dec 2013 08:03:23 -0500 Date: Wed, 4 Dec 2013 14:04:20 +0100 From: Oleg Nesterov To: Andrew Morton Cc: David Rientjes , "Eric W. Biederman" , Frederic Weisbecker , Mandeep Singh Baines , "Ma, Xindong" , Michal Hocko , Sameer Nanda , Sergey Dyasly , "Tu, Xiaobing" , linux-kernel@vger.kernel.org Subject: [PATCH v2 4/4] oom_kill: add rcu_read_lock() into find_lock_task_mm() Message-ID: <20131204130420.GA6017@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20131204130351.GA5984@redhat.com> 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 find_lock_task_mm() expects it is called under rcu or tasklist lock, but it seems that at least oom_unkillable_task()->task_in_mem_cgroup() and mem_cgroup_out_of_memory()->oom_badness() can call it lockless. Perhaps we could fix the callers, but this patch simply adds rcu lock into find_lock_task_mm(). This also allows to simplify a bit one of its callers, oom_kill_process(). Signed-off-by: Oleg Nesterov --- mm/oom_kill.c | 12 ++++++++---- 1 files changed, 8 insertions(+), 4 deletions(-) diff --git a/mm/oom_kill.c b/mm/oom_kill.c index 0d8ad1e..054ff47 100644 --- a/mm/oom_kill.c +++ b/mm/oom_kill.c @@ -102,14 +102,19 @@ struct task_struct *find_lock_task_mm(struct task_struct *p) { struct task_struct *t; + rcu_read_lock(); + for_each_thread(p, t) { task_lock(t); if (likely(t->mm)) - return t; + goto found; task_unlock(t); } + t = NULL; +found: + rcu_read_unlock(); - return NULL; + return t; } /* return true if the task is not adequate as candidate victim task. */ @@ -461,10 +466,8 @@ void oom_kill_process(struct task_struct *p, gfp_t gfp_mask, int order, } read_unlock(&tasklist_lock); - rcu_read_lock(); p = find_lock_task_mm(victim); if (!p) { - rcu_read_unlock(); put_task_struct(victim); return; } else if (victim != p) { @@ -490,6 +493,7 @@ void oom_kill_process(struct task_struct *p, gfp_t gfp_mask, int order, * That thread will now get access to memory reserves since it has a * pending fatal signal. */ + rcu_read_lock(); for_each_process(p) if (p->mm == mm && !same_thread_group(p, victim) && !(p->flags & PF_KTHREAD)) { -- 1.5.5.1