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SubjectRe: [PATCH] workqueue: Fix possible unexpectedly worker wakeup before started
Hello, Lai.

On Wed, Feb 19, 2014 at 11:47:58AM +0800, Lai Jiangshan wrote:
> If a worker is wokenup unexpectedly, it will start to work incorretly.
> Although it hardly happen, we should catch it and wait for being started
> if it does happen.

Can this actually happen? If so, how?

> Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
> ---
> kernel/workqueue.c | 6 ++++++
> 1 files changed, 6 insertions(+), 0 deletions(-)
>
> diff --git a/kernel/workqueue.c b/kernel/workqueue.c
> index 82ef9f3..bee5fe1 100644
> --- a/kernel/workqueue.c
> +++ b/kernel/workqueue.c
> @@ -2284,6 +2284,12 @@ static int worker_thread(void *__worker)
> struct worker *worker = __worker;
> struct worker_pool *pool = worker->pool;
>
> + if (WARN_ON_ONCE(!(worker->flags & WORKER_STARTED))) {

And if this is something which can legitimately happen, why are we
triggering WARN on it?

> + /* The worker is wokenup unexpectedly before started */
> + mutex_lock(&pool->manager_mutex);
> + mutex_unlock(&pool->manager_mutex);

And what does these mutex cycling achieve (they need comment)?

Thanks.

--
tejun


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