From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751345AbaK0XEU (ORCPT ); Thu, 27 Nov 2014 18:04:20 -0500 Received: from mx1.redhat.com ([209.132.183.28]:33738 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751166AbaK0XET (ORCPT ); Thu, 27 Nov 2014 18:04:19 -0500 Date: Fri, 28 Nov 2014 00:04:05 +0100 From: Oleg Nesterov To: Andrew Morton Cc: Cong Wang , David Rientjes , Michal Hocko , "Rafael J. Wysocki" , Tejun Heo , linux-kernel@vger.kernel.org Subject: [PATCH 1/2] oom: don't assume that a coredumping thread will exit soon Message-ID: <20141127230405.GA25093@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20141127230349.GA25075@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 oom_kill.c assumes that PF_EXITING task should exit and free the memory soon. This is wrong in many ways and one important case is the coredump. A task can sleep in exit_mm() "forever" while the coredumping sub-thread can need more memory. Change the PF_EXITING checks to take SIGNAL_GROUP_COREDUMP into account, we add the new trivial helper for that. Note: this is only the first step, this patch doesn't try to solve other problems. For example it doesn't try to clear the wrongly set TIF_MEMDIE (SIGNAL_GROUP_COREDUMP check is obviously racy), fatal_signal_pending() can be false positive, etc. Signed-off-by: Oleg Nesterov --- mm/oom_kill.c | 12 +++++++++--- 1 files changed, 9 insertions(+), 3 deletions(-) diff --git a/mm/oom_kill.c b/mm/oom_kill.c index 5340f6b..7af33b5 100644 --- a/mm/oom_kill.c +++ b/mm/oom_kill.c @@ -254,6 +254,12 @@ static enum oom_constraint constrained_alloc(struct zonelist *zonelist, } #endif +static inline bool task_will_free_mem(struct task_struct *task) +{ + return (task->flags & PF_EXITING) && + !(task->signal->flags & SIGNAL_GROUP_COREDUMP); +} + enum oom_scan_t oom_scan_process_thread(struct task_struct *task, unsigned long totalpages, const nodemask_t *nodemask, bool force_kill) @@ -281,7 +287,7 @@ enum oom_scan_t oom_scan_process_thread(struct task_struct *task, if (oom_task_origin(task)) return OOM_SCAN_SELECT; - if (task->flags & PF_EXITING && !force_kill) { + if (task_will_free_mem(task) && !force_kill) { /* * If this task is not being ptraced on exit, then wait for it * to finish before killing some other task unnecessarily. @@ -443,7 +449,7 @@ void oom_kill_process(struct task_struct *p, gfp_t gfp_mask, int order, * If the task is already exiting, don't alarm the sysadmin or kill * its children or threads, just set TIF_MEMDIE so it can die quickly */ - if (p->flags & PF_EXITING) { + if (task_will_free_mem(p)) { set_tsk_thread_flag(p, TIF_MEMDIE); put_task_struct(p); return; @@ -649,7 +655,7 @@ void out_of_memory(struct zonelist *zonelist, gfp_t gfp_mask, * select it. The goal is to allow it to allocate so that it may * quickly exit and free its memory. */ - if (fatal_signal_pending(current) || current->flags & PF_EXITING) { + if (fatal_signal_pending(current) || task_will_free_mem(current)) { set_thread_flag(TIF_MEMDIE); return; } -- 1.5.5.1