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=-26.3 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_GIT,USER_IN_DEF_DKIM_WL 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 4D67EC4338F for ; Wed, 28 Jul 2021 01:22:51 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 35A3560F23 for ; Wed, 28 Jul 2021 01:22:51 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234026AbhG1BWu (ORCPT ); Tue, 27 Jul 2021 21:22:50 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57380 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233008AbhG1BWt (ORCPT ); Tue, 27 Jul 2021 21:22:49 -0400 Received: from mail-pj1-x104a.google.com (mail-pj1-x104a.google.com [IPv6:2607:f8b0:4864:20::104a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 99A0CC061757 for ; Tue, 27 Jul 2021 18:22:48 -0700 (PDT) Received: by mail-pj1-x104a.google.com with SMTP id mu13-20020a17090b388db02901769cf3d01aso1229259pjb.7 for ; Tue, 27 Jul 2021 18:22:48 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:message-id:mime-version:subject:from:to:cc; bh=KmGPLe7yWyGg+5xBmJJBJmFQBI3nGe2qI3u2htSZRc8=; b=nuhUlmTMHBefTVNrgYI+UtWHFhAeUZ55sBhNa0QX9fumm4mflb1V6DbSoHCRW6t06r onMeMgc+EcsYHFi0X4PcAOFTt1Ca4GWOMdzhbbiOrGVTrb0+gtM9N1DnIZxhXv8HlftC DJSqiUVC7neopxxFodop5YR1Gled3AwZiXE7gKa9y/fs3sAr5ZECb/Puda3R9v+/bkI+ nb00mP95Ua0jnx3xuMqkU9/WGjDryEYGUuk5L5v/oC3oUWmi5Da3evvFfquWnPH15h+y PKiZUtUG5Qb4p9eZ7PCfY2pcvyOh2brxBgAENIFwi2xJrsLT1ESfcW03z9V4K8U/cP8u YJPw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:message-id:mime-version:subject:from:to:cc; bh=KmGPLe7yWyGg+5xBmJJBJmFQBI3nGe2qI3u2htSZRc8=; b=jma3MlQMHbpbA3J1uc3bPAEek70dBZ0IHekaGE7uz3fJuXOpXSkGnTyFb2hajaQPAl ck7oXlPrmuyEb8EI6WHsGQWLVr++hrgVoj6TClCRtrf/dO+3MSV0YCM78yP6oKyIBVPO NfNSiIA1S5UE+VOjjnr3Ufr/5zDyOZMkB/5ytzSE8+KwC1DqVTHgMRqERMfKIbLn3D4B jqaU8MH6fS+uv0J1x8WRhNZF3BBpTcClRn+Kmwqse/RHHGaiGV27r4S+NoWqjnv6zHiY rZXL/kLwNEpZ0qWsny89Fi3dYgyaoICW+p0/679ehn6Hs/0Buh2y9eIH/BbhRVgpU9Hd VGDg== X-Gm-Message-State: AOAM530ecnvY5JcDnX1WB9FwPJJS9jp/7L/thrOLlAEo7W1xLIEa7L5+ 6LquggcdBY5LL3qITvY43UaHGerMr7pMSA== X-Google-Smtp-Source: ABdhPJzw9SOwdwjV0WZ2MCa+P1MfPRGVFwKeQeenXU6wTjTUOggsSdYuRL9EvyC6Q1eQ/xQYrxL51Z0AKSHI7w== X-Received: from shakeelb.svl.corp.google.com ([2620:15c:2cd:202:40e2:477f:2bc7:716c]) (user=shakeelb job=sendgmr) by 2002:a17:90a:3489:: with SMTP id p9mr13744551pjb.4.1627435368045; Tue, 27 Jul 2021 18:22:48 -0700 (PDT) Date: Tue, 27 Jul 2021 18:22:43 -0700 Message-Id: <20210728012243.3369123-1-shakeelb@google.com> Mime-Version: 1.0 X-Mailer: git-send-email 2.32.0.432.gabb21c7263-goog Subject: [PATCH] memcg: cleanup racy sum avoidance code From: Shakeel Butt To: Michal Hocko , Johannes Weiner , Roman Gushchin Cc: Andrew Morton , cgroups@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Shakeel Butt Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org We used to have per-cpu memcg and lruvec stats and the readers have to traverse and sum the stats from each cpu. This summing was racy and may expose transient negative values. So, an explicit check was added to avoid such scenarios. Now these stats are moved to rstat infrastructure and are no more per-cpu, so we can remove the fixup for transient negative values. Signed-off-by: Shakeel Butt --- include/linux/memcontrol.h | 15 ++------------- 1 file changed, 2 insertions(+), 13 deletions(-) diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h index 7028d8e4a3d7..5f2a39a43d47 100644 --- a/include/linux/memcontrol.h +++ b/include/linux/memcontrol.h @@ -991,30 +991,19 @@ static inline void mod_memcg_state(struct mem_cgroup *memcg, static inline unsigned long memcg_page_state(struct mem_cgroup *memcg, int idx) { - long x = READ_ONCE(memcg->vmstats.state[idx]); -#ifdef CONFIG_SMP - if (x < 0) - x = 0; -#endif - return x; + return READ_ONCE(memcg->vmstats.state[idx]); } static inline unsigned long lruvec_page_state(struct lruvec *lruvec, enum node_stat_item idx) { struct mem_cgroup_per_node *pn; - long x; if (mem_cgroup_disabled()) return node_page_state(lruvec_pgdat(lruvec), idx); pn = container_of(lruvec, struct mem_cgroup_per_node, lruvec); - x = READ_ONCE(pn->lruvec_stats.state[idx]); -#ifdef CONFIG_SMP - if (x < 0) - x = 0; -#endif - return x; + return READ_ONCE(pn->lruvec_stats.state[idx]); } static inline unsigned long lruvec_page_state_local(struct lruvec *lruvec, -- 2.32.0.432.gabb21c7263-goog