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=-8.9 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 17A08C43441 for ; Sat, 17 Nov 2018 00:39:18 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C6E6E208E7 for ; Sat, 17 Nov 2018 00:39:17 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="Ru0kcIM4" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org C6E6E208E7 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 S1730796AbeKQKxP (ORCPT ); Sat, 17 Nov 2018 05:53:15 -0500 Received: from mail-pf1-f193.google.com ([209.85.210.193]:35215 "EHLO mail-pf1-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729714AbeKQKxO (ORCPT ); Sat, 17 Nov 2018 05:53:14 -0500 Received: by mail-pf1-f193.google.com with SMTP id v9-v6so12151732pff.2; Fri, 16 Nov 2018 16:38:38 -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=g+x0Z8u1o4aOWMcidhd9IWCml4xwrNc4H7EaMb8VtdA=; b=Ru0kcIM4utPcHoBGfTYmpaShtLyReVfIpaLr6Zj+WPIlxZKnKd7zIQiCVjzDexKfgs IzhMurfmNkQAWAy7yZn4zAr2xbuF0CdESDr2V1/entgxH7URYTOJ3O2oguyhuIYGgJP1 wQsyPuEBilOFqZTCVTchgjtalPoEMIl8hhKIPJt1nGGdiKWInZiXslus0fg9OhEpBPik oXdBX+2kIXfAFhbn1bLeBm7EV5FaMttE1d5Bdjykz+sfbSGuCSSium5m1hkEg0gPBpaA lSMTqkmxYCv2Ma0YV/5Ix1lhSZxrpvYWfS0UMPdzDdCbk+kT2clNnMlzwR7VYHShF1lS E67A== 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=g+x0Z8u1o4aOWMcidhd9IWCml4xwrNc4H7EaMb8VtdA=; b=HdlgyuLNQZPqeRy2lnRwPUhMhdP0KDPxqkTqQQdH4/lhjAYXyOHz2+TNl5rfr2GNih ozx3so1Spy4sjSqZdvRslzTNHdTsN7N0G9xwvUQ8aEdUI2VSAE9lMKTalrzC+ITeFRAQ hbXvIJ4eUqYIpiRRzhrxicHVgE2vSlXKZNz869TK04CRtTLa1IJ4ZCAzQpOy2uN3KTXI WNoiN6VvUFDQx1XkxJKMEPGI/3uuO7a3PFMZMPD7LbukgnzWPgp6lICtOlxdvPwONEMZ cSOGv39nh3VtgVsB+KQj5zg7IfSTZVzT78T1q1uF1xpojUsHPSOZi/tJesMdngQqZaIT OLsg== X-Gm-Message-State: AGRZ1gK+ni7rLoC+lXSGiMF1XxybxOk9P891wS+hlXfSyX01tTuEBHRZ tp5CNKD/Ozva1/KNW656NRelVLUNFbo= X-Google-Smtp-Source: AJdET5eIf/+hAiYWlrnR4HuiB3wU7YYAKWLLB3QxBl4jrpcKniC1TJq6p5uMyugwFCUlctevGagPsQ== X-Received: by 2002:a63:64c:: with SMTP id 73mr11809507pgg.373.1542415118072; Fri, 16 Nov 2018 16:38:38 -0800 (PST) Received: from tower.thefacebook.com ([2620:10d:c090:200::4:2b73]) by smtp.gmail.com with ESMTPSA id f6sm1981177pfg.188.2018.11.16.16.38.37 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Fri, 16 Nov 2018 16:38:37 -0800 (PST) From: Roman Gushchin X-Google-Original-From: Roman Gushchin To: Tejun Heo Cc: Oleg Nesterov , cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, kernel-team@fb.com, Roman Gushchin Subject: [PATCH v3 3/7] cgroup: protect cgroup->nr_(dying_)descendants by css_set_lock Date: Fri, 16 Nov 2018 16:38:26 -0800 Message-Id: <20181117003830.15344-4-guro@fb.com> X-Mailer: git-send-email 2.17.2 In-Reply-To: <20181117003830.15344-1-guro@fb.com> References: <20181117003830.15344-1-guro@fb.com> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Now the number of descendant cgroups and the number of dying descendant cgroups are 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. Signed-off-by: Roman Gushchin Cc: Tejun Heo Cc: kernel-team@fb.com --- include/linux/cgroup-defs.h | 3 +++ kernel/cgroup/cgroup.c | 20 ++++++++++++++++---- 2 files changed, 19 insertions(+), 4 deletions(-) diff --git a/include/linux/cgroup-defs.h b/include/linux/cgroup-defs.h index 22254c1fe1c5..9e77559c7f49 100644 --- a/include/linux/cgroup-defs.h +++ b/include/linux/cgroup-defs.h @@ -346,6 +346,9 @@ 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 css_set_lock. */ int nr_descendants; int nr_dying_descendants; diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c index ef3442555b32..2241cb1d1238 100644 --- a/kernel/cgroup/cgroup.c +++ b/kernel/cgroup/cgroup.c @@ -3409,11 +3409,15 @@ static int cgroup_events_show(struct seq_file *seq, void *v) static int cgroup_stat_show(struct seq_file *seq, void *v) { struct cgroup *cgroup = seq_css(seq)->cgroup; + int nr_descendants, nr_dying_descendants; - seq_printf(seq, "nr_descendants %d\n", - cgroup->nr_descendants); - seq_printf(seq, "nr_dying_descendants %d\n", - cgroup->nr_dying_descendants); + spin_lock_irq(&css_set_lock); + nr_descendants = cgroup->nr_descendants; + nr_dying_descendants = cgroup->nr_dying_descendants; + spin_unlock_irq(&css_set_lock); + + seq_printf(seq, "nr_descendants %d\n", nr_descendants); + seq_printf(seq, "nr_dying_descendants %d\n", nr_dying_descendants); return 0; } @@ -4684,9 +4688,11 @@ 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; @@ -4899,12 +4905,14 @@ static struct cgroup *cgroup_create(struct cgroup *parent) if (ret) goto out_idr_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); @@ -4956,6 +4964,7 @@ static bool cgroup_check_hierarchy_limits(struct cgroup *parent) lockdep_assert_held(&cgroup_mutex); + spin_lock_irq(&css_set_lock); for (cgroup = parent; cgroup; cgroup = cgroup_parent(cgroup)) { if (cgroup->nr_descendants >= cgroup->max_descendants) goto fail; @@ -4968,6 +4977,7 @@ static bool cgroup_check_hierarchy_limits(struct cgroup *parent) ret = true; fail: + spin_unlock_irq(&css_set_lock); return ret; } @@ -5187,10 +5197,12 @@ 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