From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-io1-f69.google.com (mail-io1-f69.google.com [209.85.166.69]) by kanga.kvack.org (Postfix) with ESMTP id 22E4C8E0004 for ; Fri, 7 Dec 2018 07:43:22 -0500 (EST) Received: by mail-io1-f69.google.com with SMTP id b21so3460461ioj.8 for ; Fri, 07 Dec 2018 04:43:22 -0800 (PST) Received: from www262.sakura.ne.jp (www262.sakura.ne.jp. [202.181.97.72]) by mx.google.com with ESMTPS id s196si1866471itc.63.2018.12.07.04.43.19 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 07 Dec 2018 04:43:20 -0800 (PST) Subject: Re: [RFC PATCH 2/2] memcg: do not report racy no-eligible OOM tasks References: <20181022071323.9550-1-mhocko@kernel.org> <20181022071323.9550-3-mhocko@kernel.org> <20181026142531.GA27370@cmpxchg.org> <20181026192551.GC18839@dhcp22.suse.cz> <20181026193304.GD18839@dhcp22.suse.cz> <20181106124224.GM27423@dhcp22.suse.cz> <8725e3b3-3752-fa7f-a88f-5ff4f5b6eace@i-love.sakura.ne.jp> <20181107100810.GA27423@dhcp22.suse.cz> From: Tetsuo Handa Message-ID: <8a71ecd8-e7bc-25de-184f-dfda511ee0d1@i-love.sakura.ne.jp> Date: Fri, 7 Dec 2018 21:43:07 +0900 MIME-Version: 1.0 In-Reply-To: <20181107100810.GA27423@dhcp22.suse.cz> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Michal Hocko , Johannes Weiner Cc: linux-mm@kvack.org, David Rientjes , Andrew Morton , LKML On 2018/11/07 19:08, Michal Hocko wrote: > On Wed 07-11-18 18:45:27, Tetsuo Handa wrote: >> On 2018/11/06 21:42, Michal Hocko wrote: >>> On Tue 06-11-18 18:44:43, Tetsuo Handa wrote: >>> [...] >>>> diff --git a/mm/memcontrol.c b/mm/memcontrol.c >>>> index 6e1469b..a97648a 100644 >>>> --- a/mm/memcontrol.c >>>> +++ b/mm/memcontrol.c >>>> @@ -1382,8 +1382,13 @@ static bool mem_cgroup_out_of_memory(struct mem_cgroup *memcg, gfp_t gfp_mask, >>>> }; >>>> bool ret; >>>> >>>> - mutex_lock(&oom_lock); >>>> - ret = out_of_memory(&oc); >>>> + if (mutex_lock_killable(&oom_lock)) >>>> + return true; >>>> + /* >>>> + * A few threads which were not waiting at mutex_lock_killable() can >>>> + * fail to bail out. Therefore, check again after holding oom_lock. >>>> + */ >>>> + ret = fatal_signal_pending(current) || out_of_memory(&oc); >>>> mutex_unlock(&oom_lock); >>>> return ret; >>>> } >>> >>> If we are goging with a memcg specific thingy then I really prefer >>> tsk_is_oom_victim approach. Or is there any reason why this is not >>> suitable? >>> >> >> Why need to wait for mark_oom_victim() called after slow printk() messages? >> >> If current thread got Ctrl-C and thus current thread can terminate, what is >> nice with waiting for the OOM killer? If there are several OOM events in >> multiple memcg domains waiting for completion of printk() messages? I don't >> see points with waiting for oom_lock, for try_charge() already allows current >> thread to terminate due to fatal_signal_pending() test. > > 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. > > Johaness? > No response for one month. When can we get to an RCU stall problem syzbot reported?