From nobody Thu Jan 1 07:32:19 2026 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 824A4C07545 for ; Tue, 24 Oct 2023 14:20:00 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1343618AbjJXOUA (ORCPT ); Tue, 24 Oct 2023 10:20:00 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59182 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234567AbjJXOT6 (ORCPT ); Tue, 24 Oct 2023 10:19:58 -0400 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 C8243B6 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> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.10 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" 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 cp= usets") 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; =20 @@ -234,14 +234,14 @@ void inc_dl_tasks_cs(struct task_struct *p) { struct cpuset *cs =3D task_cs(p); =20 - cs->nr_deadline_tasks++; + atomic_inc(&cs->nr_deadline_tasks); } =20 void dec_dl_tasks_cs(struct task_struct *p) { struct cpuset *cs =3D task_cs(p); =20 - cs->nr_deadline_tasks--; + atomic_dec(&cs->nr_deadline_tasks); } =20 /* 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; =20 - if (cs->nr_deadline_tasks =3D=3D 0) + if (atomic_read(&cs->nr_deadline_tasks) =3D=3D 0) return; =20 css_task_iter_start(&cs->css, 0, &it); @@ -2721,8 +2721,8 @@ static void cpuset_attach(struct cgroup_taskset *tset) cs->old_mems_allowed =3D cpuset_attach_nodemask_to; =20 if (cs->nr_migrate_dl_tasks) { - cs->nr_deadline_tasks +=3D cs->nr_migrate_dl_tasks; - oldcs->nr_deadline_tasks -=3D 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); } =20 --=20 2.39.3