Hello,
On Thu, Apr 17, 2014 at 07:34:08AM +0800, Lai Jiangshan wrote:
> Before the rescuer is picked to running, the works of the @pwq
> may be processed by some other workers, and destroy_workqueue()
> may called at the same time. This may result a nasty situation
> that rescuer may exit with non-empty mayday list.
>
> It is no harm currently, destroy_workqueue() can safely to free
> them all(workqueue&pwqs) togerther, since the rescuer is stopped.
> No rescuer nor mayday-timer can access the mayday list.
>
> But it is nasty and error-prone in future develop. Fix it.
>
> Signed-off-by: Lai Jiangshan <la...@cn.fujitsu.com>
> ---
> kernel/workqueue.c | 12 ++++++------
> 1 files changed, 6 insertions(+), 6 deletions(-)
>
> diff --git a/kernel/workqueue.c b/kernel/workqueue.c
> index 0ee63af..832125f 100644
> --- a/kernel/workqueue.c
> +++ b/kernel/workqueue.c
> @@ -2409,12 +2409,6 @@ static int rescuer_thread(void *__rescuer)
> repeat:
> set_current_state(TASK_INTERRUPTIBLE);
>
> - if (kthread_should_stop()) {
> - __set_current_state(TASK_RUNNING);
> - rescuer->task->flags &= ~PF_WQ_WORKER;
> - return 0;
> - }
> -
> /* see whether any pwq is asking for help */
> spin_lock_irq(&wq_mayday_lock);
>
> @@ -2459,6 +2453,12 @@ repeat:
>
> spin_unlock_irq(&wq_mayday_lock);
>
> + if (kthread_should_stop()) {
> + __set_current_state(TASK_RUNNING);
> + rescuer->task->flags &= ~PF_WQ_WORKER;
> + return 0;
> + }
> +
I don't think this is reliable. What if mayday requests take place
between wq_mayday_lock and kthread_should_stop() check? We'll
probably need to run through mayday list after checking should_stop.
Thanks.
--
tejun
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