From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from lindbergh.monkeyblade.net (lindbergh.monkeyblade.net [23.128.96.19]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 8B247200CC for ; Tue, 24 Oct 2023 14:19:14 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="NFjNA2zn" Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D33A9109 for ; Tue, 24 Oct 2023 07:19:12 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1698157151; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding; bh=FzoE+t/xa/RBIqwiGU6BCs2knHD6IlCAWWR1/udDPMk=; b=NFjNA2znSaaNjKQPiEvpoJPhSaMuhAJDLz4EU/fOijLG7StTKY/xnMBSryel7SsKCyKim4 HFxRDuOlWQNmBzbbpUFpNCYZ+Z52MYj52O8HjRrxkZlIBrxJ8uBQ+xkVUScbIMyykCWvil iRzoJXxOgN3uZTO3yXc/Y7ckoOcx3is= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-5-MkTUii1tPdefPQcswqZvkw-1; Tue, 24 Oct 2023 10:19:06 -0400 X-MC-Unique: MkTUii1tPdefPQcswqZvkw-1 Received: from smtp.corp.redhat.com (int-mx10.intmail.prod.int.rdu2.redhat.com [10.11.54.10]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 4109C101A53B; Tue, 24 Oct 2023 14:19:05 +0000 (UTC) Received: from llong.com (unknown [10.22.10.127]) by smtp.corp.redhat.com (Postfix) with ESMTP id 2E7C3492BFB; Tue, 24 Oct 2023 14:19:02 +0000 (UTC) From: Waiman Long To: Tejun Heo , Zefan Li , Johannes Weiner Cc: linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, Juri Lelli , Peter Zijlstra , Ingo Molnar , Qais Yousef , Hao Luo , Dietmar Eggemann , Steven Rostedt , Xia Fukun , Waiman Long Subject: [PATCH v2] cgroup/cpuset: Change nr_deadline_tasks to an atomic_t value Date: Tue, 24 Oct 2023 10:18:34 -0400 Message-Id: <20231024141834.4073262-1-longman@redhat.com> Precedence: bulk X-Mailing-List: cgroups@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.10 The nr_deadline_tasks field in cpuset structure was introduced by commit 6c24849f5515 ("sched/cpuset: Keep track of SCHED_DEADLINE task in cpusets"). Unlike nr_migrate_dl_tasks which is only modified under cpuset_mutex, nr_deadline_tasks can be updated under two different locks - cpuset_mutex in most cases or css_set_lock in cgroup_exit(). As a result, data races can happen leading to incorrect nr_deadline_tasks value. Since it is not practical to somehow take cpuset_mutex in cgroup_exit(), the easy way out to avoid this possible race condition is by making nr_deadline_tasks an atomic_t value. Fixes: 6c24849f5515 ("sched/cpuset: Keep track of SCHED_DEADLINE task in cpusets") Reported-by: Xia Fukun Signed-off-by: Waiman Long --- kernel/cgroup/cpuset.c | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-) diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c index 58ec88efa4f8..3f3da468f058 100644 --- a/kernel/cgroup/cpuset.c +++ b/kernel/cgroup/cpuset.c @@ -174,7 +174,7 @@ struct cpuset { * number of SCHED_DEADLINE tasks attached to this cpuset, so that we * know when to rebuild associated root domain bandwidth information. */ - int nr_deadline_tasks; + atomic_t nr_deadline_tasks; int nr_migrate_dl_tasks; u64 sum_migrate_dl_bw; @@ -234,14 +234,14 @@ void inc_dl_tasks_cs(struct task_struct *p) { struct cpuset *cs = task_cs(p); - cs->nr_deadline_tasks++; + atomic_inc(&cs->nr_deadline_tasks); } void dec_dl_tasks_cs(struct task_struct *p) { struct cpuset *cs = task_cs(p); - cs->nr_deadline_tasks--; + atomic_dec(&cs->nr_deadline_tasks); } /* bits in struct cpuset flags field */ @@ -1071,7 +1071,7 @@ static void dl_update_tasks_root_domain(struct cpuset *cs) struct css_task_iter it; struct task_struct *task; - if (cs->nr_deadline_tasks == 0) + if (atomic_read(&cs->nr_deadline_tasks) == 0) return; css_task_iter_start(&cs->css, 0, &it); @@ -2721,8 +2721,8 @@ static void cpuset_attach(struct cgroup_taskset *tset) cs->old_mems_allowed = cpuset_attach_nodemask_to; if (cs->nr_migrate_dl_tasks) { - cs->nr_deadline_tasks += cs->nr_migrate_dl_tasks; - oldcs->nr_deadline_tasks -= cs->nr_migrate_dl_tasks; + atomic_add(cs->nr_migrate_dl_tasks, &cs->nr_deadline_tasks); + atomic_sub(cs->nr_migrate_dl_tasks, &oldcs->nr_deadline_tasks); reset_migrate_dl_data(cs); } -- 2.39.3