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=-16.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,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 8DA71C4338F for ; Mon, 26 Jul 2021 15:00:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6A00660BD3 for ; Mon, 26 Jul 2021 15:00:30 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234860AbhGZOUA (ORCPT ); Mon, 26 Jul 2021 10:20:00 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36468 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234778AbhGZOTy (ORCPT ); Mon, 26 Jul 2021 10:19:54 -0400 Received: from mail-qt1-x82b.google.com (mail-qt1-x82b.google.com [IPv6:2607:f8b0:4864:20::82b]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 100FAC061757 for ; Mon, 26 Jul 2021 08:00:22 -0700 (PDT) Received: by mail-qt1-x82b.google.com with SMTP id k13so7157131qth.10 for ; Mon, 26 Jul 2021 08:00:22 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=cmpxchg-org.20150623.gappssmtp.com; s=20150623; h=from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=xTTsptuLITxPc+Owajv0QCvUN6VmzjQA4sTb/kLyZME=; b=ZXLe+pV1dgrpJxW8gR0RgPwPUehS8IrE/2Vbou8UHcmjEUrqODo0mbUUtREDLuboHI uRYwy1cK4J2lucpZS2lkrz+Yw3WhqxYpAkUM404nyr8nhUs+xbXAzDBhgicYHjJ02tcT P7TwXco+KKFQYqfCwlG7Pa+rFK8sjhe3zkhUEIpLvEhU1x/8TfOIdLv3UNg30/xApIS9 n+idNUq/UTyY5HU1LEGAlJPZWfKdyKAYAIaaFhvqhVJnPZULfAhZMEDr+qzP1/Amj40Q BVflhSLUWnZN5aqLPa75Q9QA+mvqr+1FOMZjDpEEW8gOwUNQA5DRllSRQyw3V6m1xd8f cVfQ== 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:mime-version :content-transfer-encoding; bh=xTTsptuLITxPc+Owajv0QCvUN6VmzjQA4sTb/kLyZME=; b=Je1MYYEtdiOl6QsMpGG2ZSiJi2EIm12KREGOlP8mK5eUguATgD0gpZp6kpBESDGTeS WawD7GY7jA0ucpU0b+UhrQXvH+zt7A+yFnwr064Qsg/eBNYCM71sUq/jnetqiqN3s2Mp ALtyREi6YwtODEMUP5NZgBRV3sC1jI8xU+PDcPEdKrm1CfKe5NKaTMl8ttwvOKiJooTA wzNGEPJ8RQ8XrMbVphG1R30rfUAtKPW25QDHubKDHvrU4El4yD20hLmXwbpO98CrJ1Nz MXipR4ax208dRE760yiY23O4XrK/BEXb8Wo8CQwCuVKdO88i+dcmTrzmtUaUTFMOvw/N jkCg== X-Gm-Message-State: AOAM531+GTL5EEBS8An1nl6cEi7/o7rMjjDU2zPI3ZAyXj61uUnEAYY8 XklxcBOq25Kz0ev/a1XPhjVFHA== X-Google-Smtp-Source: ABdhPJxUmmX4dY9GgbrCAU62sFsuKrKt/V1WzL+nrW4HxYYqVOvANMZBVBRtyJKBVfb1X3SNBJmi+w== X-Received: by 2002:ac8:66ca:: with SMTP id m10mr14787845qtp.171.1627311621182; Mon, 26 Jul 2021 08:00:21 -0700 (PDT) Received: from localhost ([2620:10d:c091:480::1:e732]) by smtp.gmail.com with ESMTPSA id h10sm99931qka.83.2021.07.26.08.00.20 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 26 Jul 2021 08:00:20 -0700 (PDT) From: Johannes Weiner To: Andrew Morton Cc: Dan Carpenter , linux-mm@kvack.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, kernel-team@fb.com Subject: [PATCH] mm: memcontrol: fix blocking rstat function called from atomic cgroup1 thresholding code Date: Mon, 26 Jul 2021 11:00:19 -0400 Message-Id: <20210726150019.251820-1-hannes@cmpxchg.org> X-Mailer: git-send-email 2.32.0 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Dan Carpenter reports: The patch 2d146aa3aa84: "mm: memcontrol: switch to rstat" from Apr 29, 2021, leads to the following static checker warning: kernel/cgroup/rstat.c:200 cgroup_rstat_flush() warn: sleeping in atomic context mm/memcontrol.c 3572 static unsigned long mem_cgroup_usage(struct mem_cgroup *memcg, bool swap) 3573 { 3574 unsigned long val; 3575 3576 if (mem_cgroup_is_root(memcg)) { 3577 cgroup_rstat_flush(memcg->css.cgroup); ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ This is from static analysis and potentially a false positive. The problem is that mem_cgroup_usage() is called from __mem_cgroup_threshold() which holds an rcu_read_lock(). And the cgroup_rstat_flush() function can sleep. 3578 val = memcg_page_state(memcg, NR_FILE_PAGES) + 3579 memcg_page_state(memcg, NR_ANON_MAPPED); 3580 if (swap) 3581 val += memcg_page_state(memcg, MEMCG_SWAP); 3582 } else { 3583 if (!swap) 3584 val = page_counter_read(&memcg->memory); 3585 else 3586 val = page_counter_read(&memcg->memsw); 3587 } 3588 return val; 3589 } __mem_cgroup_threshold() indeed holds the rcu lock. In addition, the thresholding code is invoked during stat changes, and those contexts have irqs disabled as well. If the lock breaking occurs inside the flush function, it will result in a sleep from an atomic context. Use the irsafe flushing variant in mem_cgroup_usage() to fix this. Fixes: 2d146aa3aa84 ("mm: memcontrol: switch to rstat") Cc: Reported-by: Dan Carpenter Signed-off-by: Johannes Weiner --- mm/memcontrol.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index ae1f5d0cb581..eb8e87c4833f 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -3574,7 +3574,8 @@ static unsigned long mem_cgroup_usage(struct mem_cgroup *memcg, bool swap) unsigned long val; if (mem_cgroup_is_root(memcg)) { - cgroup_rstat_flush(memcg->css.cgroup); + /* mem_cgroup_threshold() calls here from irqsafe context */ + cgroup_rstat_flush_irqsafe(memcg->css.cgroup); val = memcg_page_state(memcg, NR_FILE_PAGES) + memcg_page_state(memcg, NR_ANON_MAPPED); if (swap) -- 2.32.0