From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1423506AbcBQObn (ORCPT ); Wed, 17 Feb 2016 09:31:43 -0500 Received: from www262.sakura.ne.jp ([202.181.97.72]:64553 "EHLO www262.sakura.ne.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1423215AbcBQObl (ORCPT ); Wed, 17 Feb 2016 09:31:41 -0500 From: Tetsuo Handa To: mhocko@kernel.org, akpm@linux-foundation.org Cc: rientjes@google.com, mgorman@suse.de, oleg@redhat.com, torvalds@linux-foundation.org, hughd@google.com, andrea@kernel.org, riel@redhat.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Tetsuo Handa , Johannes Weiner Subject: [PATCH v2] mm,oom: don't abort on exiting processes when selecting a victim. Date: Wed, 17 Feb 2016 23:31:25 +0900 Message-Id: <1455719485-7730-1-git-send-email-penguin-kernel@I-love.SAKURA.ne.jp> X-Mailer: git-send-email 1.8.3.1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Currently, oom_scan_process_thread() returns OOM_SCAN_ABORT when there is a thread which is exiting. But it is possible that that thread is blocked at down_read(&mm->mmap_sem) in exit_mm() called from do_exit() whereas one of threads sharing that memory is doing a GFP_KERNEL allocation between down_write(&mm->mmap_sem) and up_write(&mm->mmap_sem) (e.g. mmap()). ---------- T1 T2 Calls mmap() Calls _exit(0) Arrives at vm_mmap_pgoff() Arrives at do_exit() Gets PF_EXITING via exit_signals() Calls down_write(&mm->mmap_sem) Calls do_mmap_pgoff() Calls down_read(&mm->mmap_sem) from exit_mm() Calls out of memory via a GFP_KERNEL allocation but oom_scan_process_thread(T1) returns OOM_SCAN_ABORT ---------- down_read(&mm->mmap_sem) by T1 is waiting for up_write(&mm->mmap_sem) by T2 while oom_scan_process_thread() by T2 is waiting for T1 to set T1->mm = NULL. Under such situation, the OOM killer does not choose a victim, which results in silent OOM livelock problem. This patch changes oom_scan_process_thread() not to return OOM_SCAN_ABORT when there is a thread which is exiting. Signed-off-by: Tetsuo Handa Signed-off-by: Johannes Weiner --- mm/oom_kill.c | 3 --- 1 file changed, 3 deletions(-) diff --git a/mm/oom_kill.c b/mm/oom_kill.c index cf87153..6e6abaf 100644 --- a/mm/oom_kill.c +++ b/mm/oom_kill.c @@ -292,9 +292,6 @@ enum oom_scan_t oom_scan_process_thread(struct oom_control *oc, if (oom_task_origin(task)) return OOM_SCAN_SELECT; - if (task_will_free_mem(task) && !is_sysrq_oom(oc)) - return OOM_SCAN_ABORT; - return OOM_SCAN_OK; } -- 1.8.3.1