Received-SPF: pass (google.com: domain of linux-kernel+bounces-92916-linux.lists.archive=gmail.com@vger.kernel.org designates 2604:1380:40f1:3f00::1 as permitted sender) client-ip=2604:1380:40f1:3f00::1;
From: "Uladzislau Rezki (Sony)" <urezki@gmail.com>
To: "Paul E . McKenney" <paulmck@kernel.org>
Cc: RCU <rcu@vger.kernel.org>,
	Neeraj upadhyay <Neeraj.Upadhyay@amd.com>,
	Boqun Feng <boqun.feng@gmail.com>,
	Hillf Danton <hdanton@sina.com>,
	Joel Fernandes <joel@joelfernandes.org>,
	LKML <linux-kernel@vger.kernel.org>,
	Uladzislau Rezki <urezki@gmail.com>,
	Oleksiy Avramchenko <oleksiy.avramchenko@sony.com>,
	Frederic Weisbecker <frederic@kernel.org>
Subject: [PATCH 2/2] rcu: Allocate WQ with WQ_MEM_RECLAIM bit set
Date: Tue,  5 Mar 2024 20:57:20 +0100
Message-Id: <20240305195720.42687-2-urezki@gmail.com>
In-Reply-To: <20240305195720.42687-1-urezki@gmail.com>
References: <20240305195720.42687-1-urezki@gmail.com>
Precedence: bulk
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit

synchronize_rcu() users have to be processed regardless
of memory pressure so our private WQ needs to have at least
one execution context what WQ_MEM_RECLAIM flag guarantees.

Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
---
 kernel/rcu/tree.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 475647620b12..59881a68dd26 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -1581,6 +1581,7 @@ static void rcu_sr_put_wait_head(struct llist_node *node)
 /* Disabled by default. */
 static int rcu_normal_wake_from_gp;
 module_param(rcu_normal_wake_from_gp, int, 0644);
+static struct workqueue_struct *sync_wq;
 
 static void rcu_sr_normal_complete(struct llist_node *node)
 {
@@ -1679,7 +1680,7 @@ static void rcu_sr_normal_gp_cleanup(void)
 	 * of outstanding users(if still left) and releasing wait-heads
 	 * added by rcu_sr_normal_gp_init() call.
 	 */
-	queue_work(system_highpri_wq, &rcu_state.srs_cleanup_work);
+	queue_work(sync_wq, &rcu_state.srs_cleanup_work);
 }
 
 /*
@@ -5584,6 +5585,9 @@ void __init rcu_init(void)
 	rcu_gp_wq = alloc_workqueue("rcu_gp", WQ_MEM_RECLAIM, 0);
 	WARN_ON(!rcu_gp_wq);
 
+	sync_wq = alloc_workqueue("sync_wq", WQ_MEM_RECLAIM, 0);
+	WARN_ON(!sync_wq);
+
 	/* Fill in default value for rcutree.qovld boot parameter. */
 	/* -After- the rcu_node ->lock fields are initialized! */
 	if (qovld < 0)
-- 
2.39.2