workqueue: protect wq->nr_drainers and ->flags with wq->mutex

We're expanding wq->mutex to cover all fields specific to each
workqueue with the end goal of replacing pwq_lock which will make
locking simpler and easier to understand.

wq->nr_drainers and ->flags are specific to each workqueue.  Protect
->nr_drainers and ->flags with wq->mutex instead of pool_mutex.

tj: Rebased on top of the current dev branch.  Updated description.

Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index d448edae35131e9ee6865a0da8b8d754a3a9debe..3ac2c4d856074e8f811533db34b383d530210946 100644 (file)
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -226,7 +226,7 @@ struct wq_device;
  * the appropriate worker_pool through its pool_workqueues.
  */
 struct workqueue_struct {
-       unsigned int            flags;          /* PL: WQ_* flags */
+       unsigned int            flags;          /* WQ: WQ_* flags */
        struct pool_workqueue __percpu *cpu_pwqs; /* I: per-cpu pwq's */
        struct list_head        pwqs;           /* WR: all pwqs of this wq */
        struct list_head        list;           /* PL: list of all workqueues */
@@ -242,7 +242,7 @@ struct workqueue_struct {
        struct list_head        maydays;        /* MD: pwqs requesting rescue */
        struct worker           *rescuer;       /* I: rescue worker */
 
-       int                     nr_drainers;    /* PL: drain in progress */
+       int                     nr_drainers;    /* WQ: drain in progress */
        int                     saved_max_active; /* PW: saved pwq max_active */
 
 #ifdef CONFIG_SYSFS
@@ -2684,10 +2684,10 @@ void drain_workqueue(struct workqueue_struct *wq)
         * hotter than drain_workqueue() and already looks at @wq->flags.
         * Use __WQ_DRAINING so that queue doesn't have to check nr_drainers.
         */
-       mutex_lock(&wq_pool_mutex);
+       mutex_lock(&wq->mutex);
        if (!wq->nr_drainers++)
                wq->flags |= __WQ_DRAINING;
-       mutex_unlock(&wq_pool_mutex);
+       mutex_unlock(&wq->mutex);
 reflush:
        flush_workqueue(wq);
 
@@ -2714,10 +2714,10 @@ reflush:
 
        local_irq_enable();
 
-       mutex_lock(&wq_pool_mutex);
+       mutex_lock(&wq->mutex);
        if (!--wq->nr_drainers)
                wq->flags &= ~__WQ_DRAINING;
-       mutex_unlock(&wq_pool_mutex);
+       mutex_unlock(&wq->mutex);
 }
 EXPORT_SYMBOL_GPL(drain_workqueue);