workqueue: fix locking in retry path of maybe_create_worker()

maybe_create_worker() mismanaged locking when worker creation fails
and it has to retry.  Fix locking and simplify lock manipulation.

Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: Yong Zhang <yong.zhang@windriver.com>

diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index 20d6237d7498bf389d5c9a9d95dd728d69c7781b..aca94726e20a937d2bb9d4b711da9c3fbda75bcf 100644 (file)
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -1442,14 +1442,14 @@ static bool maybe_create_worker(struct global_cwq *gcwq)
        if (!need_to_create_worker(gcwq))
                return false;
 restart:
+       spin_unlock_irq(&gcwq->lock);
+
        /* if we don't make progress in MAYDAY_INITIAL_TIMEOUT, call for help */
        mod_timer(&gcwq->mayday_timer, jiffies + MAYDAY_INITIAL_TIMEOUT);
 
        while (true) {
                struct worker *worker;
 
-               spin_unlock_irq(&gcwq->lock);
-
                worker = create_worker(gcwq, true);
                if (worker) {
                        del_timer_sync(&gcwq->mayday_timer);
@@ -1462,15 +1462,13 @@ restart:
                if (!need_to_create_worker(gcwq))
                        break;
 
-               spin_unlock_irq(&gcwq->lock);
                __set_current_state(TASK_INTERRUPTIBLE);
                schedule_timeout(CREATE_COOLDOWN);
-               spin_lock_irq(&gcwq->lock);
+
                if (!need_to_create_worker(gcwq))
                        break;
        }
 
-       spin_unlock_irq(&gcwq->lock);
        del_timer_sync(&gcwq->mayday_timer);
        spin_lock_irq(&gcwq->lock);
        if (need_to_create_worker(gcwq))