From patchwork Wed Aug 11 03:06:02 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Waiman Long X-Patchwork-Id: 12429881 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=-16.5 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 88473C4338F for ; Wed, 11 Aug 2021 03:06:47 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6D6CC60E09 for ; Wed, 11 Aug 2021 03:06:47 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233066AbhHKDHJ (ORCPT ); Tue, 10 Aug 2021 23:07:09 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:35069 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232994AbhHKDHI (ORCPT ); Tue, 10 Aug 2021 23:07:08 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1628651205; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:in-reply-to:in-reply-to:references:references; bh=rxmUDgi/eSAWBp+aX5tEZpY9hepwTSXrcnetuW0lBu8=; b=TcGoTsS+EMliZJRf4cQkAnhvOB97Z5AQTFPH/prk7Q374QYVfKvs/iMPPFX/22yAuzHgaR Bonq+69fmr+JMp2sg6FnWrvhdZcbHvnw+qfVH61rbXD+Z6tRgofjyflK/XXUWvloH/NubE +2HTWZ86YpiUqn2Im6JZiAs+KJ049yI= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-4-iVwq80K7Nh6Y_EPgqaPVQQ-1; Tue, 10 Aug 2021 23:06:42 -0400 X-MC-Unique: iVwq80K7Nh6Y_EPgqaPVQQ-1 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 7563A107ACF5; Wed, 11 Aug 2021 03:06:40 +0000 (UTC) Received: from llong.com (unknown [10.22.17.215]) by smtp.corp.redhat.com (Postfix) with ESMTP id 04ACB669ED; Wed, 11 Aug 2021 03:06:37 +0000 (UTC) From: Waiman Long To: Tejun Heo , Zefan Li , Johannes Weiner , Jonathan Corbet , Shuah Khan Cc: cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, linux-kselftest@vger.kernel.org, Andrew Morton , Roman Gushchin , Phil Auld , Peter Zijlstra , Juri Lelli , Frederic Weisbecker , Marcelo Tosatti , =?utf-8?q?Michal_Koutn=C3=BD?= , Waiman Long Subject: [PATCH v4 1/6] cgroup/cpuset: Enable event notification when partition state changes Date: Tue, 10 Aug 2021 23:06:02 -0400 Message-Id: <20210811030607.13824-2-longman@redhat.com> In-Reply-To: <20210811030607.13824-1-longman@redhat.com> References: <20210811030607.13824-1-longman@redhat.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 Precedence: bulk List-ID: X-Mailing-List: linux-kselftest@vger.kernel.org A valid cpuset partition can become invalid if all its CPUs are offlined or somehow removed. This can happen through external events without "cpuset.cpus.partition" being touched at all. Users that rely on the property of a partition being present do not currently have a simple way to get such an event notified other than constant periodic polling which is both inefficient and cumbersome. To make life easier for those users, event notification is now enabled for "cpuset.cpus.partition" whenever its state changes. Suggested-by: Tejun Heo Signed-off-by: Waiman Long --- kernel/cgroup/cpuset.c | 46 ++++++++++++++++++++++++++++++++---------- 1 file changed, 35 insertions(+), 11 deletions(-) diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c index 65258102e030..fcc11f2d3b5b 100644 --- a/kernel/cgroup/cpuset.c +++ b/kernel/cgroup/cpuset.c @@ -160,6 +160,9 @@ struct cpuset { */ int use_parent_ecpus; int child_ecpus_count; + + /* Handle for cpuset.cpus.partition */ + struct cgroup_file partition_file; }; /* @@ -263,6 +266,16 @@ static inline int is_partition_root(const struct cpuset *cs) return cs->partition_root_state > 0; } +/* + * Send notification event of whenever partition_root_state changes. + */ +static inline void notify_partition_change(struct cpuset *cs, + int old_prs, int new_prs) +{ + if (old_prs != new_prs) + cgroup_file_notify(&cs->partition_file); +} + static struct cpuset top_cpuset = { .flags = ((1 << CS_ONLINE) | (1 << CS_CPU_EXCLUSIVE) | (1 << CS_MEM_EXCLUSIVE)), @@ -1148,7 +1161,7 @@ static int update_parent_subparts_cpumask(struct cpuset *cpuset, int cmd, struct cpuset *parent = parent_cs(cpuset); int adding; /* Moving cpus from effective_cpus to subparts_cpus */ int deleting; /* Moving cpus from subparts_cpus to effective_cpus */ - int new_prs; + int old_prs, new_prs; bool part_error = false; /* Partition error? */ percpu_rwsem_assert_held(&cpuset_rwsem); @@ -1184,7 +1197,7 @@ static int update_parent_subparts_cpumask(struct cpuset *cpuset, int cmd, * A cpumask update cannot make parent's effective_cpus become empty. */ adding = deleting = false; - new_prs = cpuset->partition_root_state; + old_prs = new_prs = cpuset->partition_root_state; if (cmd == partcmd_enable) { cpumask_copy(tmp->addmask, cpuset->cpus_allowed); adding = true; @@ -1274,7 +1287,7 @@ static int update_parent_subparts_cpumask(struct cpuset *cpuset, int cmd, parent->subparts_cpus); } - if (!adding && !deleting && (new_prs == cpuset->partition_root_state)) + if (!adding && !deleting && (new_prs == old_prs)) return 0; /* @@ -1302,9 +1315,11 @@ static int update_parent_subparts_cpumask(struct cpuset *cpuset, int cmd, parent->nr_subparts_cpus = cpumask_weight(parent->subparts_cpus); - if (cpuset->partition_root_state != new_prs) + if (old_prs != new_prs) cpuset->partition_root_state = new_prs; + spin_unlock_irq(&callback_lock); + notify_partition_change(cpuset, old_prs, new_prs); return cmd == partcmd_update; } @@ -1326,7 +1341,7 @@ static void update_cpumasks_hier(struct cpuset *cs, struct tmpmasks *tmp) struct cpuset *cp; struct cgroup_subsys_state *pos_css; bool need_rebuild_sched_domains = false; - int new_prs; + int old_prs, new_prs; rcu_read_lock(); cpuset_for_each_descendant_pre(cp, pos_css, cs) { @@ -1366,8 +1381,8 @@ static void update_cpumasks_hier(struct cpuset *cs, struct tmpmasks *tmp) * update_tasks_cpumask() again for tasks in the parent * cpuset if the parent's subparts_cpus changes. */ - new_prs = cp->partition_root_state; - if ((cp != cs) && new_prs) { + old_prs = new_prs = cp->partition_root_state; + if ((cp != cs) && old_prs) { switch (parent->partition_root_state) { case PRS_DISABLED: /* @@ -1438,10 +1453,11 @@ static void update_cpumasks_hier(struct cpuset *cs, struct tmpmasks *tmp) } } - if (new_prs != cp->partition_root_state) + if (new_prs != old_prs) cp->partition_root_state = new_prs; spin_unlock_irq(&callback_lock); + notify_partition_change(cp, old_prs, new_prs); WARN_ON(!is_in_v2_mode() && !cpumask_equal(cp->cpus_allowed, cp->effective_cpus)); @@ -2023,6 +2039,7 @@ static int update_prstate(struct cpuset *cs, int new_prs) spin_lock_irq(&callback_lock); cs->partition_root_state = new_prs; spin_unlock_irq(&callback_lock); + notify_partition_change(cs, old_prs, new_prs); } free_cpumasks(NULL, &tmpmask); @@ -2708,6 +2725,7 @@ static struct cftype dfl_files[] = { .write = sched_partition_write, .private = FILE_PARTITION_ROOT, .flags = CFTYPE_NOT_ON_ROOT, + .file_offset = offsetof(struct cpuset, partition_file), }, { @@ -3103,11 +3121,17 @@ static void cpuset_hotplug_update_tasks(struct cpuset *cs, struct tmpmasks *tmp) */ if ((parent->partition_root_state == PRS_ERROR) || cpumask_empty(&new_cpus)) { + int old_prs; + update_parent_subparts_cpumask(cs, partcmd_disable, NULL, tmp); - spin_lock_irq(&callback_lock); - cs->partition_root_state = PRS_ERROR; - spin_unlock_irq(&callback_lock); + old_prs = cs->partition_root_state; + if (old_prs != PRS_ERROR) { + spin_lock_irq(&callback_lock); + cs->partition_root_state = PRS_ERROR; + spin_unlock_irq(&callback_lock); + notify_partition_change(cs, old_prs, PRS_ERROR); + } } cpuset_force_rebuild(); }