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=-9.0 required=3.0 tests=INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT 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 5E6E5ECDE43 for ; Mon, 22 Oct 2018 07:13:47 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2CCAA20658 for ; Mon, 22 Oct 2018 07:13:47 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 2CCAA20658 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727657AbeJVPbB (ORCPT ); Mon, 22 Oct 2018 11:31:01 -0400 Received: from mail-pf1-f194.google.com ([209.85.210.194]:43530 "EHLO mail-pf1-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727579AbeJVPbB (ORCPT ); Mon, 22 Oct 2018 11:31:01 -0400 Received: by mail-pf1-f194.google.com with SMTP id q1-v6so2130176pfh.10 for ; Mon, 22 Oct 2018 00:13:44 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=FBCBxQHOTmvZgHJl60t6jyJTwJfcDyQfW3eSyeZ8neA=; b=UDQPK+zWTtGMk5+nYP+8JJChs23KFf539SRaWit0rpo/6pF692hx4pylh8JI7TEF70 /9gpiqp4Q/xOQCiN0i5c4Gq7xVF6ABEXxfIBeFGnl3ros/443MrEtGiRJyMDhyUNRQdW /Loll1WpdSl8yjR3vnO4Ogjh3slV0uIy4WVQdkHJj0Lm5ykFPBPB+rPHIklACFVQrL9H /L5ojzFwpANPyyzCLQs1B61RSNSJGygqRlorCEfwgfIZN0wr+PfKvNDrB/SKj/X8F2Er sNq6Rl2lQp32v7aThHW0jBAqJlMSem+NGdVW1UErRKpGO5FlNENddeFh9BdQzuk1ibtT 309g== X-Gm-Message-State: ABuFfogKxTgIC1cnwjsR2IlDnKifFsTm0MGvNIy0TtXMfApXqCTT3jOI Q41qhA+FusQSg6L1Ah2ud3M= X-Google-Smtp-Source: ACcGV6064Z1dWqa7QMCXfgEb9cpfEDaa6ZH2gbgOOmik96tlPssDIV7b2W3tmlzucX76u01TUKPNKw== X-Received: by 2002:a62:569d:: with SMTP id h29-v6mr16163789pfj.42.1540192424428; Mon, 22 Oct 2018 00:13:44 -0700 (PDT) Received: from tiehlicka.suse.cz (prg-ext-pat.suse.com. [213.151.95.130]) by smtp.gmail.com with ESMTPSA id c79-v6sm38097542pfc.92.2018.10.22.00.13.42 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 22 Oct 2018 00:13:43 -0700 (PDT) From: Michal Hocko To: Cc: Johannes Weiner , Tetsuo Handa , David Rientjes , Andrew Morton , LKML , Michal Hocko Subject: [RFC PATCH 2/2] memcg: do not report racy no-eligible OOM tasks Date: Mon, 22 Oct 2018 09:13:23 +0200 Message-Id: <20181022071323.9550-3-mhocko@kernel.org> X-Mailer: git-send-email 2.19.1 In-Reply-To: <20181022071323.9550-1-mhocko@kernel.org> References: <20181022071323.9550-1-mhocko@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Michal Hocko Tetsuo has reported [1] that a single process group memcg might easily swamp the log with no-eligible oom victim reports due to race between the memcg charge and oom_reaper Thread 1 Thread2 oom_reaper try_charge try_charge mem_cgroup_out_of_memory mutex_lock(oom_lock) mem_cgroup_out_of_memory mutex_lock(oom_lock) out_of_memory select_bad_process oom_kill_process(current) wake_oom_reaper oom_reap_task MMF_OOM_SKIP->victim mutex_unlock(oom_lock) out_of_memory select_bad_process # no task If Thread1 didn't race it would bail out from try_charge and force the charge. We can achieve the same by checking tsk_is_oom_victim inside the oom_lock and therefore close the race. [1] http://lkml.kernel.org/r/bb2074c0-34fe-8c2c-1c7d-db71338f1e7f@i-love.sakura.ne.jp Signed-off-by: Michal Hocko --- mm/memcontrol.c | 14 +++++++++++++- 1 file changed, 13 insertions(+), 1 deletion(-) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index e79cb59552d9..a9dfed29967b 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -1380,10 +1380,22 @@ 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); + + /* + * multi-threaded tasks might race with oom_reaper and gain + * MMF_OOM_SKIP before reaching out_of_memory which can lead + * to out_of_memory failure if the task is the last one in + * memcg which would be a false possitive failure reported + */ + if (tsk_is_oom_victim(current)) + goto unlock; + ret = out_of_memory(&oc); + +unlock: mutex_unlock(&oom_lock); return ret; } -- 2.19.1