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>

1 files changed, 9 insertions, 5 deletions

diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index 9e2ec4ca415a..756761480a1a 100644
--- 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);