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Subject[PATCH 2/2] workqueue: Keep activate-order equals to queue_work()-order
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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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