Messages in this thread Patch in this message | | | From | Lai Jiangshan <> | Subject | [PATCH 2/2] workqueue: Keep activate-order equals to queue_work()-order | Date | Tue, 18 Sep 2012 16:36:53 +0800 |
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The whole workqueue.c keeps activate-order equals to queue_work()-order in any given cwq except workqueue_set_max_active().
If this order is not kept, something may be not good:
first_work_fn() { release some resource; } second_work_fn() { wait and request the resource; use resource; }
1. user queues the first work. # ->max_active is low, is queued on ->delayed_works. 2. someone increases the >max_active via workqueue_set_max_active() 3. user queues the second work. # queued on cwq->pool.
When the second work is launched to execute, it waits the first work to release the resource. But the first work is still in ->delayed_works, it waits the first work to finish and them it can be activated.
It is bad. we fix it by activating the first work in the step 2.
I can't fully determine that it is workqueue's responsibility or the user's responsibility. If it is workqueue's responsibility, the patch needs go to -stable. If it is user's responsibility. it is a nice cleanup, it can go to for-next. I prefer it is workqueue's responsibility.
Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com> --- kernel/workqueue.c | 2 +- 1 files changed, 1 insertions(+), 1 deletions(-)
diff --git a/kernel/workqueue.c b/kernel/workqueue.c index d0ca063..8783414 100644 --- a/kernel/workqueue.c +++ b/kernel/workqueue.c @@ -3458,7 +3458,7 @@ void workqueue_set_max_active(struct workqueue_struct *wq, int max_active) if (!(wq->flags & WQ_FREEZABLE) || !(gcwq->flags & GCWQ_FREEZING)) - get_cwq(gcwq->cpu, wq)->max_active = max_active; + cwq_set_max_active(get_cwq(gcwq->cpu, wq), max_active); spin_unlock_irq(&gcwq->lock); } -- 1.7.4.4
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