workqueue: Only assign rescuer work when really needed

If the pwq does not need rescue (normal workers have been created or
become available), the rescuer can immediately move on to other stalled
pwqs.

Signed-off-by: Lai Jiangshan <[email protected]>
Signed-off-by: Tejun Heo <[email protected]>

Author: Lai Jiangshan

kernel/workqueue.c

@@ -3442,6 +3442,10 @@ static bool assign_rescuer_work(struct pool_workqueue *pwq, struct worker *rescu
 	struct worker_pool *pool = pwq->pool;
 	struct work_struct *work, *n;
 
+	/* need rescue? */
+	if (!pwq->nr_active || !need_to_create_worker(pool))
+		return false;
+
 	/*
 	 * Slurp in all works issued via this workqueue and
 	 * process'em.