From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932460Ab3LDNDT (ORCPT ); Wed, 4 Dec 2013 08:03:19 -0500 Received: from mx1.redhat.com ([209.132.183.28]:60682 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932285Ab3LDNDR (ORCPT ); Wed, 4 Dec 2013 08:03:17 -0500 Date: Wed, 4 Dec 2013 14:04:16 +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 3/4] oom_kill: has_intersects_mems_allowed() needs rcu_read_lock() Message-ID: <20131204130416.GA6014@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 At least out_of_memory() calls has_intersects_mems_allowed() without even rcu_read_lock(), this is obviously buggy. Add the necessary rcu_read_lock(). This means that we can not simply return from the loop, we need "bool ret" and "break". While at it, swap the names of task_struct's (the argument and the local). This cleanups the code a little bit and avoids the unnecessary initialization. Signed-off-by: Oleg Nesterov Reviewed-and-Tested-by: Sergey Dyasly Reviewed-by: Sameer Nanda --- mm/oom_kill.c | 19 +++++++++++-------- 1 files changed, 11 insertions(+), 8 deletions(-) diff --git a/mm/oom_kill.c b/mm/oom_kill.c index 96d7945..0d8ad1e 100644 --- a/mm/oom_kill.c +++ b/mm/oom_kill.c @@ -47,18 +47,20 @@ static DEFINE_SPINLOCK(zone_scan_lock); #ifdef CONFIG_NUMA /** * has_intersects_mems_allowed() - check task eligiblity for kill - * @tsk: task struct of which task to consider + * @start: task struct of which task to consider * @mask: nodemask passed to page allocator for mempolicy ooms * * Task eligibility is determined by whether or not a candidate task, @tsk, * shares the same mempolicy nodes as current if it is bound by such a policy * and whether or not it has the same set of allowed cpuset nodes. */ -static bool has_intersects_mems_allowed(struct task_struct *tsk, +static bool has_intersects_mems_allowed(struct task_struct *start, const nodemask_t *mask) { - struct task_struct *start = tsk; + struct task_struct *tsk; + bool ret = false; + rcu_read_lock(); for_each_thread(start, tsk) { if (mask) { /* @@ -67,19 +69,20 @@ static bool has_intersects_mems_allowed(struct task_struct *tsk, * mempolicy intersects current, otherwise it may be * needlessly killed. */ - if (mempolicy_nodemask_intersects(tsk, mask)) - return true; + ret = mempolicy_nodemask_intersects(tsk, mask); } else { /* * This is not a mempolicy constrained oom, so only * check the mems of tsk's cpuset. */ - if (cpuset_mems_allowed_intersects(current, tsk)) - return true; + ret = cpuset_mems_allowed_intersects(current, tsk); } + if (ret) + break; } + rcu_read_unlock(); - return false; + return ret; } #else static bool has_intersects_mems_allowed(struct task_struct *tsk, -- 1.5.5.1