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workqueue: reject adjusting max_active or applying attrs to ordered workqueues

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Adjusting max_active of or applying new workqueue_attrs to an ordered
workqueue breaks its ordering guarantee.  The former is obvious.  The
latter is because applying attrs creates a new pwq (pool_workqueue)
and there is no ordering constraint between the old and new pwqs.

Make apply_workqueue_attrs() and workqueue_set_max_active() trigger
WARN_ON() if those operations are requested on an ordered workqueue
and fail / ignore respectively.

Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Lai Jiangshan <laijs@cn.fujitsu.com>
This commit is contained in:
Tejun Heo 2013-03-12 11:30:04 -07:00
parent 618b01eb42
commit 8719dceae2
2 changed files with 11 additions and 1 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

3
include/linux/workqueue.h
View file

@ -295,6 +295,7 @@ enum {
WQ_CPU_INTENSIVE = 1 << 5, /* cpu instensive workqueue */ WQ_CPU_INTENSIVE = 1 << 5, /* cpu instensive workqueue */
__WQ_DRAINING = 1 << 16, /* internal: workqueue is draining */ __WQ_DRAINING = 1 << 16, /* internal: workqueue is draining */
__WQ_ORDERED = 1 << 17, /* internal: workqueue is ordered */
WQ_MAX_ACTIVE = 512, /* I like 512, better ideas? */ WQ_MAX_ACTIVE = 512, /* I like 512, better ideas? */
WQ_MAX_UNBOUND_PER_CPU = 4, /* 4 * #cpus for unbound wq */ WQ_MAX_UNBOUND_PER_CPU = 4, /* 4 * #cpus for unbound wq */
@ -397,7 +398,7 @@ __alloc_workqueue_key(const char *fmt, unsigned int flags, int max_active,
* Pointer to the allocated workqueue on success, %NULL on failure. * Pointer to the allocated workqueue on success, %NULL on failure.
*/ */
#define alloc_ordered_workqueue(fmt, flags, args...) \ #define alloc_ordered_workqueue(fmt, flags, args...) \
alloc_workqueue(fmt, WQ_UNBOUND | (flags), 1, ##args) alloc_workqueue(fmt, WQ_UNBOUND | __WQ_ORDERED | (flags), 1, ##args)
#define create_workqueue(name) \ #define create_workqueue(name) \
alloc_workqueue((name), WQ_MEM_RECLAIM, 1) alloc_workqueue((name), WQ_MEM_RECLAIM, 1)

9
kernel/workqueue.c
View file

@ -3494,9 +3494,14 @@ int apply_workqueue_attrs(struct workqueue_struct *wq,
struct pool_workqueue *pwq, *last_pwq; struct pool_workqueue *pwq, *last_pwq;
struct worker_pool *pool; struct worker_pool *pool;
/* only unbound workqueues can change attributes */
if (WARN_ON(!(wq->flags & WQ_UNBOUND))) if (WARN_ON(!(wq->flags & WQ_UNBOUND)))
return -EINVAL; return -EINVAL;
/* creating multiple pwqs breaks ordering guarantee */
if (WARN_ON((wq->flags & __WQ_ORDERED) && !list_empty(&wq->pwqs)))
return -EINVAL;
pwq = kmem_cache_zalloc(pwq_cache, GFP_KERNEL); pwq = kmem_cache_zalloc(pwq_cache, GFP_KERNEL);
if (!pwq) if (!pwq)
return -ENOMEM; return -ENOMEM;
@ -3752,6 +3757,10 @@ void workqueue_set_max_active(struct workqueue_struct *wq, int max_active)
{ {
struct pool_workqueue *pwq; struct pool_workqueue *pwq;
/* disallow meddling with max_active for ordered workqueues */
if (WARN_ON(wq->flags & __WQ_ORDERED))
return;
max_active = wq_clamp_max_active(max_active, wq->flags, wq->name); max_active = wq_clamp_max_active(max_active, wq->flags, wq->name);
spin_lock_irq(&workqueue_lock); spin_lock_irq(&workqueue_lock);