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=-8.8 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,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 426B7C04EB8 for ; Fri, 30 Nov 2018 23:49:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 0276020834 for ; Fri, 30 Nov 2018 23:49:33 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="JThfV7kp" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 0276020834 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=gmail.com 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 S1726893AbeLALA0 (ORCPT ); Sat, 1 Dec 2018 06:00:26 -0500 Received: from mail-pl1-f196.google.com ([209.85.214.196]:39364 "EHLO mail-pl1-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726852AbeLAK65 (ORCPT ); Sat, 1 Dec 2018 05:58:57 -0500 Received: by mail-pl1-f196.google.com with SMTP id 101so3531375pld.6; Fri, 30 Nov 2018 15:47:57 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=from:to:cc:subject:date:message-id:in-reply-to:references; bh=/h4U+0DlXHetF6XB/+D6rzr4Gg58Kl4UP4B7kNYPeno=; b=JThfV7kp9wcDzrPZgdTbabbZpSVI9ItSk8wpytvn7gublh82rCVNJCNegNGUWFzSa9 Y45i1Xye15z/9mArt2XiZRxQIMX8Wov4/aLURF6CHH73guSQIxKvZollYo4uuF7czSZZ nITwdevuuth3Bdo278SY3QMNUXp9WA/1SqxH/8dADzCWDLeEY0PKWvppCkffvmqCo40R HLcT2jshxHhN0cy60zW1jTiFl71YjACtAaTdrAEcmKIMpEM9pPeq3RCdhOE+dkoTH04Y v7VyFBdH4B6dtMmjzSMIpXQAoeqsUaLsoYZsFH/2VJsswK9f7IYOAt5U++kGcunyPq+3 7gcA== 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; bh=/h4U+0DlXHetF6XB/+D6rzr4Gg58Kl4UP4B7kNYPeno=; b=VoZ7sUVXZU++DTtnziIC9F8cfQIZdNA8SWJS4xMv8STbO18tFQbRc5YEI7l9qn0/I7 eFMyPnkLHa0HGdpKLmMfBcPrE0VPb+pNc1KyPFAvZBhgq41Nt8nlJe+aAw8XcD7VSYrW BtDANSLCA5oU0uQ1VqmkVN0XaKpkRRqL4SBt8zswXGi6VK9I5NmjK5/lZHNq9emL3EnH RT+GO4eNwmiNpZUg2YND5G3VBdqsfOkBYdJcvtQmrMx+Nl9BWNSB8doTP+T5KRnip3Up 84JsBt88qJiR7xCeQl5kh60zI+mhVKcIcdnAv91dqoUhQHIcnwjb0jgWpM86ZtAC0ymX Cekw== X-Gm-Message-State: AA+aEWY5HFEXQj31RjNCKjmsgHk3mdenn+iaDVcnzUyAOGi1tHUu8ces KHTUePvpSqj2EQSoTKiuOG8= X-Google-Smtp-Source: AFSGD/U2s02inVCloo1rMj03UW06OtnoIHTLeNtEKvPEWOvIWkPRAvQ07YyG9W74tkLfYS9uxwhCQQ== X-Received: by 2002:a17:902:722:: with SMTP id 31mr7588186pli.271.1543621676709; Fri, 30 Nov 2018 15:47:56 -0800 (PST) Received: from castle.tfbnw.net ([2620:10d:c090:180::1:2b61]) by smtp.gmail.com with ESMTPSA id e188sm9556742pfg.130.2018.11.30.15.47.55 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Fri, 30 Nov 2018 15:47:56 -0800 (PST) From: Roman Gushchin X-Google-Original-From: Roman Gushchin To: Tejun Heo , Oleg Nesterov Cc: Dan Carpenter , Mike Rapoport , cgroups@vger.kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, kernel-team@fb.com, Roman Gushchin Subject: [PATCH v4 3/7] cgroup: protect cgroup->nr_(dying_)descendants by css_set_lock Date: Fri, 30 Nov 2018 15:47:41 -0800 Message-Id: <20181130234745.6756-4-guro@fb.com> X-Mailer: git-send-email 2.17.2 In-Reply-To: <20181130234745.6756-1-guro@fb.com> References: <20181130234745.6756-1-guro@fb.com> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The number of descendant cgroups and the number of dying descendant cgroups are currently synchronized using the cgroup_mutex. The number of descendant cgroups will be required by the cgroup v2 freezer, which will use it to determine if a cgroup is frozen (depending on total number of descendants and number of frozen descendants). It's not always acceptable to grab the cgroup_mutex, especially from quite hot paths (e.g. exit()). To avoid this, let's additionally synchronize these counters using the css_set_lock. So, it's safe to read these counters with either cgroup_mutex or css_set_lock locked, and for changing both locks should be acquired. Signed-off-by: Roman Gushchin Cc: Tejun Heo Cc: kernel-team@fb.com --- include/linux/cgroup-defs.h | 3 +++ kernel/cgroup/cgroup.c | 6 ++++++ 2 files changed, 9 insertions(+) diff --git a/include/linux/cgroup-defs.h b/include/linux/cgroup-defs.h index 8fcbae1b8db0..4327fd6e8121 100644 --- a/include/linux/cgroup-defs.h +++ b/include/linux/cgroup-defs.h @@ -348,6 +348,9 @@ struct cgroup { * Dying cgroups are cgroups which were deleted by a user, * but are still existing because someone else is holding a reference. * max_descendants is a maximum allowed number of descent cgroups. + * + * nr_descendants and nr_dying_descendants are protected + * by cgroup_mutex and css_set_lock. */ int nr_descendants; int nr_dying_descendants; diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c index 7519a4307021..f89dde50f693 100644 --- a/kernel/cgroup/cgroup.c +++ b/kernel/cgroup/cgroup.c @@ -4723,9 +4723,11 @@ static void css_release_work_fn(struct work_struct *work) if (cgroup_on_dfl(cgrp)) cgroup_rstat_flush(cgrp); + spin_lock_irq(&css_set_lock); for (tcgrp = cgroup_parent(cgrp); tcgrp; tcgrp = cgroup_parent(tcgrp)) tcgrp->nr_dying_descendants--; + spin_unlock_irq(&css_set_lock); cgroup_idr_remove(&cgrp->root->cgroup_idr, cgrp->id); cgrp->id = -1; @@ -4943,12 +4945,14 @@ static struct cgroup *cgroup_create(struct cgroup *parent) if (ret) goto out_psi_free; + spin_lock_irq(&css_set_lock); for (tcgrp = cgrp; tcgrp; tcgrp = cgroup_parent(tcgrp)) { cgrp->ancestor_ids[tcgrp->level] = tcgrp->id; if (tcgrp != cgrp) tcgrp->nr_descendants++; } + spin_unlock_irq(&css_set_lock); if (notify_on_release(parent)) set_bit(CGRP_NOTIFY_ON_RELEASE, &cgrp->flags); @@ -5233,10 +5237,12 @@ static int cgroup_destroy_locked(struct cgroup *cgrp) if (parent && cgroup_is_threaded(cgrp)) parent->nr_threaded_children--; + spin_lock_irq(&css_set_lock); for (tcgrp = cgroup_parent(cgrp); tcgrp; tcgrp = cgroup_parent(tcgrp)) { tcgrp->nr_descendants--; tcgrp->nr_dying_descendants++; } + spin_unlock_irq(&css_set_lock); cgroup1_check_for_release(parent); -- 2.17.2