Commit 0a94efb5 authored by Tejun Heo's avatar Tejun Heo
Browse files

workqueue: implicit ordered attribute should be overridable 



5c0338c6 ("workqueue: restore WQ_UNBOUND/max_active==1 to be
ordered") automatically enabled ordered attribute for unbound
workqueues w/ max_active == 1.  Because ordered workqueues reject
max_active and some attribute changes, this implicit ordered mode
broke cases where the user creates an unbound workqueue w/ max_active
== 1 and later explicitly changes the related attributes.

This patch distinguishes explicit and implicit ordered setting and
overrides from attribute changes if implict.

Signed-off-by: default avatarTejun Heo <tj@kernel.org>
Fixes: 5c0338c6 ("workqueue: restore WQ_UNBOUND/max_active==1 to be ordered")
parent 5c0338c6

include/linux/workqueue.h

+3 −1
Original line number Diff line number Diff line
@@ -323,6 +323,7 @@ enum { 


	__WQ_DRAINING		= 1 << 16, /* internal: workqueue is draining */

	__WQ_ORDERED		= 1 << 17, /* internal: workqueue is ordered */

	__WQ_ORDERED_EXPLICIT	= 1 << 18, /* internal: alloc_ordered_workqueue() */

	__WQ_LEGACY		= 1 << 18, /* internal: create*_workqueue() */



	WQ_MAX_ACTIVE		= 512,	  /* I like 512, better ideas? */
@@ -422,7 +423,8 @@ __alloc_workqueue_key(const char *fmt, unsigned int flags, int max_active, 
 * Pointer to the allocated workqueue on success, %NULL on failure.

 */

#define alloc_ordered_workqueue(fmt, flags, args...)			\

	alloc_workqueue(fmt, WQ_UNBOUND | __WQ_ORDERED | (flags), 1, ##args)

	alloc_workqueue(fmt, WQ_UNBOUND | __WQ_ORDERED |		\

			__WQ_ORDERED_EXPLICIT | (flags), 1, ##args)



#define create_workqueue(name)						\

	alloc_workqueue("%s", __WQ_LEGACY | WQ_MEM_RECLAIM, 1, (name))

kernel/workqueue.c

+9 −4
Original line number Diff line number Diff line
@@ -3744,9 +3744,13 @@ static int apply_workqueue_attrs_locked(struct workqueue_struct *wq, 
		return -EINVAL;



	/* creating multiple pwqs breaks ordering guarantee */

	if (WARN_ON((wq->flags & __WQ_ORDERED) && !list_empty(&wq->pwqs)))

	if (!list_empty(&wq->pwqs)) {

		if (WARN_ON(wq->flags & __WQ_ORDERED_EXPLICIT))

			return -EINVAL;



		wq->flags &= ~__WQ_ORDERED;

	}



	ctx = apply_wqattrs_prepare(wq, attrs);

	if (!ctx)

		return -ENOMEM;
@@ -4129,13 +4133,14 @@ void workqueue_set_max_active(struct workqueue_struct *wq, int max_active) 
	struct pool_workqueue *pwq;



	/* disallow meddling with max_active for ordered workqueues */

	if (WARN_ON(wq->flags & __WQ_ORDERED))

	if (WARN_ON(wq->flags & __WQ_ORDERED_EXPLICIT))

		return;



	max_active = wq_clamp_max_active(max_active, wq->flags, wq->name);



	mutex_lock(&wq->mutex);



	wq->flags &= ~__WQ_ORDERED;

	wq->saved_max_active = max_active;



	for_each_pwq(pwq, wq)
@@ -5263,7 +5268,7 @@ int workqueue_sysfs_register(struct workqueue_struct *wq) 
	 * attributes breaks ordering guarantee.  Disallow exposing ordered

	 * workqueues.

	 */

	if (WARN_ON(wq->flags & __WQ_ORDERED))

	if (WARN_ON(wq->flags & __WQ_ORDERED_EXPLICIT))

		return -EINVAL;



	wq->wq_dev = wq_dev = kzalloc(sizeof(*wq_dev), GFP_KERNEL);

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