From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) (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 23F933B6C0C for ; Fri, 29 May 2026 21:29:05 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.129.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780090146; cv=none; b=a+Sm7kRbveqWovhQsyj0GtlPYr9nHEyx4ehKUFNpJD9xagVQ0H5O/Bs2gHnCGV00eyAK7NAnB4N+yHmBtVxEoYBf9IAiwP+hVAHd84MvazonTsO24neNrgRY8QHKOki5zudU4DioZu7AFYFYOgMPFOc2T/l/zejuv0RTbxVKHdw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780090146; c=relaxed/simple; bh=V9DFmSDhG43eGFNXkB+UQL0h3Yfa4lT/yeGDh7pikUw=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=SDh+wECdBYChvTK5svCugpST2g98C+u6ZvlPeXnujm6SNh61+rAVJLmk7+XCfIQ5lewrY+V1Nch9TBq7omn/RU3k4UfskXE3oKwfkbHIyZNXU4pqMBtK/Da7lFzEjSVnX6/H7kbmAgOD9lLi8A4yjmvjh0LY271Tdq5CjZBdl68= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=MkuBbYso; arc=none smtp.client-ip=170.10.129.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="MkuBbYso" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1780090141; 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: in-reply-to:in-reply-to:references:references; bh=l5q566hPmN0jAjitqvJNqIepGnvrcfqAOr2eXJQ++W8=; b=MkuBbYsoopBuciO4xTqwWKrNjXDJndoiQgZS1WzROTMLrDsL9i+AMxrSEBvnTFod7DgUhS Afis2EMGcBq8NpY+FkPU57BgQD4EHifPDXurdQr/H+sG3qmhwVBiV6o/FCszQipDMVRZGF 6AE4JClIYuHFTF7WuohpY+4AVM/7oPk= Received: from mx-prod-mc-05.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-245-GdTFWSfDNUusJdRxjEUbBQ-1; Fri, 29 May 2026 17:28:57 -0400 X-MC-Unique: GdTFWSfDNUusJdRxjEUbBQ-1 X-Mimecast-MFC-AGG-ID: GdTFWSfDNUusJdRxjEUbBQ_1780090136 Received: from mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.12]) (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 mx-prod-mc-05.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id B9240195608A; Fri, 29 May 2026 21:28:55 +0000 (UTC) Received: from llong-thinkpadp16vgen1.westford.csb (unknown [10.22.64.54]) by mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 7B90819560B0; Fri, 29 May 2026 21:28:53 +0000 (UTC) From: Waiman Long To: Chen Ridong , Tejun Heo , Johannes Weiner , =?UTF-8?q?Michal=20Koutn=C3=BD?= , Peter Zijlstra Cc: cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, Aaron Tomlin , Guopeng Zhang , Waiman Long Subject: [PATCH-next v4 5/6] cgroup/cpuset: Move mpol_rebind_mm/cpuset_migrate_mm() calls inside cpuset_attach_task() Date: Fri, 29 May 2026 17:21:07 -0400 Message-ID: <20260529212108.120506-6-longman@redhat.com> In-Reply-To: <20260529212108.120506-1-longman@redhat.com> References: <20260529212108.120506-1-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 3.0 on 10.30.177.12 The cpuset_attach_task() was introduced in commit 42a11bf5c543 ("cgroup/cpuset: Make cpuset_fork() handle CLONE_INTO_CGROUP properly") to enable the CLONE_INTO_CGROUP flag of clone(2) to behave more like moving a task from one cpuset into another one. That commits didn't move the mpol_rebind_mm() and cpuset_migrate_mm() calls for group leader into cpuset_attach_task(). When the CLONE_INTO_CGROUP flag is used without CLONE_THREAD, the new task is its own group leader. So it is still not equivalent to moving task between cpusets in this case. Make CLONE_INTO_CGROUP behaves more close to cpuset_attach() by moving the mpol_rebind_mm() and cpuset_migrate_mm() calls inside cpuset_attach_task(). As a result, the following static variables will have to be updated in cpuset_fork(). - cpuset_attach_old_cs - attach_cpus_updated - attach_mems_updated - queue_task_work Signed-off-by: Waiman Long --- kernel/cgroup/cpuset.c | 89 ++++++++++++++++++++++++------------------ 1 file changed, 51 insertions(+), 38 deletions(-) diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c index 0bb63a9cda0b..a6506b94e60a 100644 --- a/kernel/cgroup/cpuset.c +++ b/kernel/cgroup/cpuset.c @@ -3171,9 +3171,12 @@ static void cpuset_cancel_attach(struct cgroup_taskset *tset) */ static cpumask_var_t cpus_attach; static nodemask_t cpuset_attach_nodemask_to; +static bool queue_task_work; static void cpuset_attach_task(struct cpuset *cs, struct task_struct *task) { + struct mm_struct *mm; + lockdep_assert_cpuset_lock_held(); if (cs != &top_cpuset) @@ -3187,24 +3190,56 @@ static void cpuset_attach_task(struct cpuset *cs, struct task_struct *task) */ WARN_ON_ONCE(set_cpus_allowed_ptr(task, cpus_attach)); + if (cpuset_v2() && !attach_mems_updated) + return; + cpuset_change_task_nodemask(task, &cpuset_attach_nodemask_to); cpuset1_update_task_spread_flags(cs, task); + + if (task != task->group_leader) + return; + + /* + * Change mm for threadgroup leader. This is expensive and may + * sleep and should be moved outside migration path proper. + */ + mm = get_task_mm(task); + if (mm) { + struct cpuset *oldcs = cpuset_attach_old_cs; + + mpol_rebind_mm(mm, &cs->effective_mems); + + /* + * old_mems_allowed is the same with mems_allowed + * here, except if this task is being moved + * automatically due to hotplug. In that case + * @mems_allowed has been updated and is empty, so + * @old_mems_allowed is the right nodesets that we + * migrate mm from. + */ + if (is_memory_migrate(cs)) { + cpuset_migrate_mm(mm, &oldcs->old_mems_allowed, + &cpuset_attach_nodemask_to); + queue_task_work = true; + } else { + mmput(mm); + } + } } static void cpuset_attach(struct cgroup_taskset *tset) { struct task_struct *task; - struct task_struct *leader; struct cgroup_subsys_state *css; struct cpuset *cs; struct cpuset *oldcs = cpuset_attach_old_cs; - bool queue_task_work = false; cgroup_taskset_first(tset, &css); cs = css_cs(css); lockdep_assert_cpus_held(); /* see cgroup_attach_lock() */ mutex_lock(&cpuset_mutex); + queue_task_work = false; /* * In the default hierarchy, enabling cpuset in the child cgroups @@ -3223,38 +3258,6 @@ static void cpuset_attach(struct cgroup_taskset *tset) cgroup_taskset_for_each(task, css, tset) cpuset_attach_task(cs, task); - /* - * Change mm for all threadgroup leaders. This is expensive and may - * sleep and should be moved outside migration path proper. Skip it - * if there is no change in effective_mems and CS_MEMORY_MIGRATE is - * not set. - */ - if (!is_memory_migrate(cs) && !attach_mems_updated) - goto out; - - cgroup_taskset_for_each_leader(leader, css, tset) { - struct mm_struct *mm = get_task_mm(leader); - - if (mm) { - mpol_rebind_mm(mm, &cs->effective_mems); - - /* - * old_mems_allowed is the same with mems_allowed - * here, except if this task is being moved - * automatically due to hotplug. In that case - * @mems_allowed has been updated and is empty, so - * @old_mems_allowed is the right nodesets that we - * migrate mm from. - */ - if (is_memory_migrate(cs)) { - cpuset_migrate_mm(mm, &oldcs->old_mems_allowed, - &cpuset_attach_nodemask_to); - queue_task_work = true; - } else - mmput(mm); - } - } - out: if (queue_task_work) schedule_flush_migrate_mm(); @@ -3688,15 +3691,14 @@ static void cpuset_cancel_fork(struct task_struct *task, struct css_set *cset) */ static void cpuset_fork(struct task_struct *task) { - struct cpuset *cs; - bool same_cs; + struct cpuset *cs, *oldcs; rcu_read_lock(); cs = task_cs(task); - same_cs = (cs == task_cs(current)); + oldcs = task_cs(current); rcu_read_unlock(); - if (same_cs) { + if (cs == oldcs) { if (cs == &top_cpuset) return; @@ -3708,7 +3710,18 @@ static void cpuset_fork(struct task_struct *task) /* CLONE_INTO_CGROUP */ mutex_lock(&cpuset_mutex); guarantee_online_mems(cs, &cpuset_attach_nodemask_to); + /* + * Assume CPUs and memory nodes are updated + * A CLONE_INTO_CGROUP operation should have taken the cgroup mutex + * and so there shouldn't be a competing cpuset_attach() operation. + */ + attach_cpus_updated = attach_mems_updated = true; + queue_task_work = false; + cpuset_attach_old_cs = oldcs; cpuset_attach_task(cs, task); + attach_cpus_updated = attach_mems_updated = false; + if (queue_task_work) + schedule_flush_migrate_mm(); dec_attach_in_progress_locked(cs); mutex_unlock(&cpuset_mutex); -- 2.54.0