From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-10.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_PASS, USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 82CEEC43612 for ; Tue, 8 Jan 2019 11:46:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 500982087F for ; Tue, 8 Jan 2019 11:46:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1546948003; bh=xmR8WpyPhxG9uusctUHR3nYbgDAH3psziXW5uUOhrtc=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=ndGgSlr+APZRcVHLhGCOFMB9gk/y3V2NUXVDMTUk5Y44v/o6ynNYm6Jd1+ORFPSMK AFm5FJCaggj2h1KNTIbr0dLyOPPhml/EjZdz+tzK2WovQEHr+UwH1zh6p+QW/CkImO PEbuDkrZn/iMIpqOcTdwkqOr1RUAXTQlsDaPRW+U= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728729AbfAHLqm (ORCPT ); Tue, 8 Jan 2019 06:46:42 -0500 Received: from mx2.suse.de ([195.135.220.15]:38238 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1727236AbfAHLql (ORCPT ); Tue, 8 Jan 2019 06:46:41 -0500 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id A5437AF21; Tue, 8 Jan 2019 11:46:40 +0000 (UTC) Date: Tue, 8 Jan 2019 12:46:39 +0100 From: Michal Hocko To: Tetsuo Handa Cc: linux-mm@kvack.org, Johannes Weiner , Andrew Morton , LKML Subject: Re: [PATCH 2/2] memcg: do not report racy no-eligible OOM tasks Message-ID: <20190108114639.GR31793@dhcp22.suse.cz> References: <20190107143802.16847-1-mhocko@kernel.org> <20190107143802.16847-3-mhocko@kernel.org> <20190108081441.GO31793@dhcp22.suse.cz> <3b105bba-3542-1d00-c6e2-52f6d125eff2@i-love.sakura.ne.jp> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <3b105bba-3542-1d00-c6e2-52f6d125eff2@i-love.sakura.ne.jp> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue 08-01-19 19:39:58, Tetsuo Handa wrote: > On 2019/01/08 17:14, Michal Hocko wrote: > >>> diff --git a/mm/memcontrol.c b/mm/memcontrol.c > >>> index af7f18b32389..90eb2e2093e7 100644 > >>> --- a/mm/memcontrol.c > >>> +++ b/mm/memcontrol.c > >>> @@ -1387,10 +1387,22 @@ static bool mem_cgroup_out_of_memory(struct mem_cgroup *memcg, gfp_t gfp_mask, > >>> .gfp_mask = gfp_mask, > >>> .order = order, > >>> }; > >>> - bool ret; > >>> + bool ret = true; > >>> > >>> mutex_lock(&oom_lock); > >> > >> And because of "[PATCH 1/2] mm, oom: marks all killed tasks as oom > >> victims", mark_oom_victim() will be called on current thread even if > >> we used mutex_lock_killable(&oom_lock) here, like you said > >> > >> mutex_lock_killable would take care of exiting task already. I would > >> then still prefer to check for mark_oom_victim because that is not racy > >> with the exit path clearing signals. I can update my patch to use > >> _killable lock variant if we are really going with the memcg specific > >> fix. > >> > >> . If current thread is not yet killed by the OOM killer but can terminate > >> without invoking the OOM killer, using mutex_lock_killable(&oom_lock) here > >> saves some processes. What is the race you are referring by "racy with the > >> exit path clearing signals" ? > > > > This is unrelated to the patch. > > Ultimately related! This is the reasoning why your patch should be preferred > over my patch. No! I've said I do not mind using mutex_lock_killable on top of this patch. I just want to have this fix minimal. -- Michal Hocko SUSE Labs