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workqueue: implicit ordered attribute should be overridable

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5c0338c687 ("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: Tejun Heo <tj@kernel.org>
Fixes: 5c0338c687 ("workqueue: restore WQ_UNBOUND/max_active==1 to be ordered")
This commit is contained in:
Tejun Heo 2017-07-23 08:36:15 -04:00
parent 5c0338c687
commit 0a94efb5ac
2 changed files with 12 additions and 5 deletions
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4
include/linux/workqueue.h
View File

@ -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))

13
kernel/workqueue.c
View File

@ -3744,8 +3744,12 @@ 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)))
return -EINVAL;
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)
@ -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);