Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932801AbaFIIwE (ORCPT ); Mon, 9 Jun 2014 04:52:04 -0400 Received: from ip4-83-240-18-248.cust.nbox.cz ([83.240.18.248]:58489 "EHLO ip4-83-240-18-248.cust.nbox.cz" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755010AbaFIIvZ (ORCPT ); Mon, 9 Jun 2014 04:51:25 -0400 From: Jiri Slaby To: stable@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Oleg Nesterov , Sergey Dyasly , Sameer Nanda , "Eric W. Biederman" , Frederic Weisbecker , Mandeep Singh Baines , "Ma, Xindong" , "Tu, Xiaobing" , Andrew Morton , Linus Torvalds , Jiri Slaby Subject: [PATCH 3.12 004/146] oom_kill: add rcu_read_lock() into find_lock_task_mm() Date: Mon, 9 Jun 2014 10:48:59 +0200 Message-Id: X-Mailer: git-send-email 1.9.3 In-Reply-To: References: In-Reply-To: References: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Oleg Nesterov 3.12-stable review patch. If anyone has any objections, please let me know. =============== commit 4d4048be8a93769350efa31d2482a038b7de73d0 upstream. 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 Cc: Sergey Dyasly Cc: Sameer Nanda Cc: "Eric W. Biederman" Cc: Frederic Weisbecker Cc: Mandeep Singh Baines Cc: "Ma, Xindong" Reviewed-by: Michal Hocko Cc: "Tu, Xiaobing" Acked-by: David Rientjes Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Jiri Slaby --- mm/oom_kill.c | 12 ++++++++---- 1 file changed, 8 insertions(+), 4 deletions(-) diff --git a/mm/oom_kill.c b/mm/oom_kill.c index 7cdd05e685dc..f5bed7f17463 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)) { -- 1.9.3 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/