Received-SPF: pass (google.com: domain of linux-kernel+bounces-58329-linux.lists.archive=gmail.com@vger.kernel.org designates 147.75.199.223 as permitted sender) client-ip=147.75.199.223;
From: Waiman Long <longman@redhat.com>
To: Tejun Heo <tj@kernel.org>,
	Lai Jiangshan <jiangshanlai@gmail.com>
Cc: linux-kernel@vger.kernel.org,
	Juri Lelli <juri.lelli@redhat.com>,
	Cestmir Kalina <ckalina@redhat.com>,
	Alex Gladkov <agladkov@redhat.com>,
	Phil Auld <pauld@redhat.com>,
	Costa Shulyupin <cshulyup@redhat.com>,
	Waiman Long <longman@redhat.com>
Subject: [PATCH wq/for-6.9 v5 3/4] kernel/workqueue: Let rescuers follow unbound wq cpumask changes
Date: Thu,  8 Feb 2024 11:10:13 -0500
Message-Id: <20240208161014.1084943-4-longman@redhat.com>
In-Reply-To: <20240208161014.1084943-1-longman@redhat.com>
References: <20240208161014.1084943-1-longman@redhat.com>
Precedence: bulk
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit

From: Juri Lelli <juri.lelli@redhat.com>

When workqueue cpumask changes are committed the associated rescuer (if
one exists) affinity is not touched and this might be a problem down the
line for isolated setups.

Make sure rescuers affinity is updated every time a workqueue cpumask
changes, so that rescuers can't break isolation.

 [longman: set_cpus_allowed_ptr() will block until the designated task
  is enqueued on an allowed CPU, no wake_up_process() needed. Also use
  the unbound_effective_cpumask() helper as suggested by Tejun.]

Signed-off-by: Juri Lelli <juri.lelli@redhat.com>
Signed-off-by: Waiman Long <longman@redhat.com>
---
 kernel/workqueue.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index e261acf258b8..8df27c496b63 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -5054,6 +5054,11 @@ static void apply_wqattrs_commit(struct apply_wqattrs_ctx *ctx)
 	/* update node_nr_active->max */
 	wq_update_node_max_active(ctx->wq, -1);
 
+	/* rescuer needs to respect wq cpumask changes */
+	if (ctx->wq->rescuer)
+		set_cpus_allowed_ptr(ctx->wq->rescuer->task,
+				     unbound_effective_cpumask(ctx->wq));
+
 	mutex_unlock(&ctx->wq->mutex);
 }
 
-- 
2.39.3