[PATCH] workqueue: remove the stale comment in pwq_unbound_release_workfn()

[PATCH] workqueue: remove the stale comment in pwq_unbound_release_workfn()

[Lai Jiangshan]

In 75ccf5950f82 ("workqueue: prepare flush_workqueue() for dynamic
creation and destrucion of unbound pool_workqueues"), a comment
about the synchronization for the pwq in pwq_unbound_release_workfn()
was added. The comment clained the flush_mutex was isn't strictly
necessary, it was correct in that time, due to the pwq was protected
by workqueue_lock.

But it is incorrect now since the wq->flush_mutex was renamed to
wq->mutex and workqueue_lock was removed, the wq->mutex is strictly
needed. But the comment was miss-updated when the synchronization
was changed.

This patch removes the incorrect comments directly, and it doesn't
add any new comment to explain why wq->mutex is needed here,
which is definitely obvious and wq->pwqs_node has "WQ" notation
in its definition which is better comment.

The old commit mentioned above also introduced a comment in link_pwq()
about the synchronization. This comment is also removed in this patch
since the whole link_pwq() is proteced by wq->mutex.

Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
---
 kernel/workqueue.c |   10 +---------
 1 files changed, 1 insertions(+), 9 deletions(-)

diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index 942103d9..b8990cf 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -3527,11 +3527,6 @@ static void pwq_unbound_release_workfn(struct work_struct *work)
 	if (WARN_ON_ONCE(!(wq->flags & WQ_UNBOUND)))
 		return;
 
-	/*
-	 * Unlink @pwq.  Synchronization against wq->mutex isn't strictly
-	 * necessary on release but do it anyway.  It's easier to verify
-	 * and consistent with the linking path.
-	 */
 	mutex_lock(&wq->mutex);
 	list_del_rcu(&pwq->pwqs_node);
 	is_last = list_empty(&wq->pwqs);
@@ -3628,10 +3623,7 @@ static void link_pwq(struct pool_workqueue *pwq)
 	if (!list_empty(&pwq->pwqs_node))
 		return;
 
-	/*
-	 * Set the matching work_color.  This is synchronized with
-	 * wq->mutex to avoid confusing flush_workqueue().
-	 */
+	/* Set the matching work_color.  */
 	pwq->work_color = wq->work_color;
 
 	/* sync max_active to the current setting */
-- 
1.7.4.4

Re: [PATCH] workqueue: remove the stale comment in pwq_unbound_release_workfn()

[Tejun Heo]

On Tue, Jul 22, 2014 at 01:04:27PM +0800, Lai Jiangshan wrote:
> In 75ccf5950f82 ("workqueue: prepare flush_workqueue() for dynamic
> creation and destrucion of unbound pool_workqueues"), a comment
> about the synchronization for the pwq in pwq_unbound_release_workfn()
> was added. The comment clained the flush_mutex was isn't strictly
> necessary, it was correct in that time, due to the pwq was protected
> by workqueue_lock.
> 
> But it is incorrect now since the wq->flush_mutex was renamed to
> wq->mutex and workqueue_lock was removed, the wq->mutex is strictly
> needed. But the comment was miss-updated when the synchronization
> was changed.
> 
> This patch removes the incorrect comments directly, and it doesn't
> add any new comment to explain why wq->mutex is needed here,
> which is definitely obvious and wq->pwqs_node has "WQ" notation
> in its definition which is better comment.
> 
> The old commit mentioned above also introduced a comment in link_pwq()
> about the synchronization. This comment is also removed in this patch
> since the whole link_pwq() is proteced by wq->mutex.
> 
> Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>

Applied to wq/for-3.17.

Thanks.

-- 
tejun