From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ed1-f69.google.com (mail-ed1-f69.google.com [209.85.208.69]) by kanga.kvack.org (Postfix) with ESMTP id B47CC8E0038 for ; Tue, 8 Jan 2019 06:46:42 -0500 (EST) Received: by mail-ed1-f69.google.com with SMTP id c53so1534650edc.9 for ; Tue, 08 Jan 2019 03:46:42 -0800 (PST) Received: from mx1.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id e9si6805019eda.224.2019.01.08.03.46.41 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 08 Jan 2019 03:46:41 -0800 (PST) Date: Tue, 8 Jan 2019 12:46:39 +0100 From: Michal Hocko 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> Sender: owner-linux-mm@kvack.org List-ID: To: Tetsuo Handa Cc: linux-mm@kvack.org, Johannes Weiner , Andrew Morton , LKML 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