rcu: Allocate WQ with WQ_MEM_RECLAIM bit set

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.

Reviewed-by: Paul E. McKenney <paulmck@kernel.org>
Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com>

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 2a270abade4df40c5b47471a60e2de217677eb9b..1d5c000e5c7aff33e1bd2f4fbd8eab5434f1d103 100644 (file)
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -1582,6 +1582,7 @@ 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)
 {
@@ -1680,7 +1681,7 @@ 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.
         */
-       schedule_work(&rcu_state.srs_cleanup_work);
+       queue_work(sync_wq, &rcu_state.srs_cleanup_work);
 }
 
 /*
@@ -5585,6 +5586,9 @@ 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)