workqueue: fix max_active handling in init_and_link_pwq()

Since 9e8cd2f589 ("workqueue: implement apply_workqueue_attrs()"),
init_and_link_pwq() may be called to initialize a new pool_workqueue
for a workqueue which is already online, but the function was setting
pwq->max_active to wq->saved_max_active without proper
synchronization.

Fix it by calling pwq_adjust_max_active() under proper locking instead
of manually setting max_active.

Signed-off-by: Tejun Heo <tj@kernel.org>

diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index 9e2ec4ca415a0bb48c45d7c8050b378c1b086ae4..756761480a1ae4514fcd8f4440f9c82815dd1567 100644 (file)
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -3771,21 +3771,25 @@ static void init_and_link_pwq(struct pool_workqueue *pwq,
        pwq->wq = wq;
        pwq->flush_color = -1;
        pwq->refcnt = 1;
-       pwq->max_active = wq->saved_max_active;
        INIT_LIST_HEAD(&pwq->delayed_works);
        INIT_LIST_HEAD(&pwq->mayday_node);
        INIT_WORK(&pwq->unbound_release_work, pwq_unbound_release_workfn);
 
-       /*
-        * Link @pwq and set the matching work_color.  This is synchronized
-        * with flush_mutex to avoid confusing flush_workqueue().
-        */
        mutex_lock(&wq->flush_mutex);
        spin_lock_irq(&workqueue_lock);
 
+       /*
+        * Set the matching work_color.  This is synchronized with
+        * flush_mutex to avoid confusing flush_workqueue().
+        */
        if (p_last_pwq)
                *p_last_pwq = first_pwq(wq);
        pwq->work_color = wq->work_color;
+
+       /* sync max_active to the current setting */
+       pwq_adjust_max_active(pwq);
+
+       /* link in @pwq */
        list_add_rcu(&pwq->pwqs_node, &wq->pwqs);
 
        spin_unlock_irq(&workqueue_lock);