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=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable 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 57372C4360F for ; Thu, 4 Apr 2019 09:31:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 28D08205F4 for ; Thu, 4 Apr 2019 09:31:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1554370282; bh=wRgNnsUMuvIVi/FLmXur1Evnh5aMf79zihpS+9xCeT8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=WpgHS5JULwT7cjcy2izSrxQKPora2hb4g7rzasTIHkua5h+feFrShX4mOSinuHtKl C2qfySUDn4kh8zimkEc5uWZEE6XdAzzrr7WU9Tx2ZnJMq33se+/2wfsDrefpaYPsZ1 xtzkgXmeYoJZq7z6VGc0blTLvXRNDnnTNYk3SpHU= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732825AbfDDJJ0 (ORCPT ); Thu, 4 Apr 2019 05:09:26 -0400 Received: from mail.kernel.org ([198.145.29.99]:48572 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731213AbfDDJJX (ORCPT ); Thu, 4 Apr 2019 05:09:23 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 0D37C2075E; Thu, 4 Apr 2019 09:09:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1554368962; bh=wRgNnsUMuvIVi/FLmXur1Evnh5aMf79zihpS+9xCeT8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=qbu/+Fvp5ZyHI+pYNalCTjqVDsaUn/i5GVqIxG2jSoyDS76/88+/vZ5yV6039WKq7 APqZP1gfKxNAwzZutPxJBFyNW4je7KkRc5LWqK7N8Gny53OayTBFEF6Ee5m+HcvWoF l+r6GcJypvmfecPzGiZnKs4pvSnm0JkRefUf176w= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Tetsuo Handa , Michal Hocko , Johannes Weiner , David Rientjes , Kirill Tkhai , Andrew Morton , Linus Torvalds , Sasha Levin Subject: [PATCH 5.0 032/246] memcg: killed threads should not invoke memcg OOM killer Date: Thu, 4 Apr 2019 10:45:32 +0200 Message-Id: <20190404084620.204840918@linuxfoundation.org> X-Mailer: git-send-email 2.21.0 In-Reply-To: <20190404084619.236418459@linuxfoundation.org> References: <20190404084619.236418459@linuxfoundation.org> User-Agent: quilt/0.65 X-stable: review X-Patchwork-Hint: ignore MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 5.0-stable review patch. If anyone has any objections, please let me know. ------------------ [ Upstream commit 7775face207922ea62a4e96b9cd45abfdc7b9840 ] If a memory cgroup contains a single process with many threads (including different process group sharing the mm) then it is possible to trigger a race when the oom killer complains that there are no oom elible tasks and complain into the log which is both annoying and confusing because there is no actual problem. The race looks as follows: P1 oom_reaper P2 try_charge try_charge mem_cgroup_out_of_memory mutex_lock(oom_lock) out_of_memory oom_kill_process(P1,P2) wake_oom_reaper mutex_unlock(oom_lock) oom_reap_task mutex_lock(oom_lock) select_bad_process # no victim The problem is more visible with many threads. Fix this by checking for fatal_signal_pending from mem_cgroup_out_of_memory when the oom_lock is already held. The oom bypass is safe because we do the same early in the try_charge path already. The situation migh have changed in the mean time. It should be safe to check for fatal_signal_pending and tsk_is_oom_victim but for a better code readability abstract the current charge bypass condition into should_force_charge and reuse it from that path. " Link: http://lkml.kernel.org/r/01370f70-e1f6-ebe4-b95e-0df21a0bc15e@i-love.sakura.ne.jp Signed-off-by: Tetsuo Handa Acked-by: Michal Hocko Acked-by: Johannes Weiner Cc: David Rientjes Cc: Kirill Tkhai Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Sasha Levin --- mm/memcontrol.c | 19 ++++++++++++++----- 1 file changed, 14 insertions(+), 5 deletions(-) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index af7f18b32389..79a7d2a06bba 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -248,6 +248,12 @@ enum res_type { iter != NULL; \ iter = mem_cgroup_iter(NULL, iter, NULL)) +static inline bool should_force_charge(void) +{ + return tsk_is_oom_victim(current) || fatal_signal_pending(current) || + (current->flags & PF_EXITING); +} + /* Some nice accessors for the vmpressure. */ struct vmpressure *memcg_to_vmpressure(struct mem_cgroup *memcg) { @@ -1389,8 +1395,13 @@ 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 = should_force_charge() || out_of_memory(&oc); mutex_unlock(&oom_lock); return ret; } @@ -2209,9 +2220,7 @@ retry: * bypass the last charges so that they can exit quickly and * free their memory. */ - if (unlikely(tsk_is_oom_victim(current) || - fatal_signal_pending(current) || - current->flags & PF_EXITING)) + if (unlikely(should_force_charge())) goto force; /* -- 2.19.1