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authorTejun Heo <tj@kernel.org>2013-03-12 11:30:04 -0700
committerTejun Heo <tj@kernel.org>2013-03-12 11:30:04 -0700
commit8719dceae2f98a578507c0f6b49c93f320bd729c (patch)
tree3132f4c6ed84ec893bcad3aaec230fa78cede95d
parent618b01eb426dd2d73a4b5e5ebc6379e4eee3b123 (diff)
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workqueue: reject adjusting max_active or applying attrs to ordered workqueues
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>
-rw-r--r--include/linux/workqueue.h3
-rw-r--r--kernel/workqueue.c9
2 files changed, 11 insertions, 1 deletions
diff --git a/include/linux/workqueue.h b/include/linux/workqueue.h
index 1751ec4c47c9..5668ab249af5 100644
--- a/include/linux/workqueue.h
+++ b/include/linux/workqueue.h
@@ -295,6 +295,7 @@ enum {
WQ_CPU_INTENSIVE = 1 << 5, /* cpu instensive workqueue */
__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_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.
*/
#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) \
alloc_workqueue((name), WQ_MEM_RECLAIM, 1)
diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index 590f4d048ec7..cecd4ffe2c40 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -3494,9 +3494,14 @@ int apply_workqueue_attrs(struct workqueue_struct *wq,
struct pool_workqueue *pwq, *last_pwq;
struct worker_pool *pool;
+ /* only unbound workqueues can change attributes */
if (WARN_ON(!(wq->flags & WQ_UNBOUND)))
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);
if (!pwq)
return -ENOMEM;
@@ -3752,6 +3757,10 @@ 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))
+ return;
+
max_active = wq_clamp_max_active(max_active, wq->flags, wq->name);
spin_lock_irq(&workqueue_lock);