[PATCH] workqueue: Upgrade queue_work_on() comment

[PATCH] workqueue: Upgrade queue_work_on() comment

[Paul E. McKenney]

The current queue_work_on() docbook comment says that the caller must
ensure that the specified CPU can't go away, but does not spell out the
consequences, which turn out to be quite mild.  Therefore expand this
comment to explicitly say that the penalty for failing to nail down the
specified CPU is that the workqueue handler might find itself executing
on some other CPU.

Cc: Tejun Heo <tj@kernel.org>
Cc: Lai Jiangshan <jiangshanlai@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index 613917bbc4e73..332361cf215fc 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -1531,7 +1531,8 @@ static void __queue_work(int cpu, struct workqueue_struct *wq,
  * @work: work to queue
  *
  * We queue the work to a specific CPU, the caller must ensure it
- * can't go away.
+ * can't go away.  Callers that fail to ensure that the specified
+ * CPU cannot go away will execute on a randomly chosen CPU.
  *
  * Return: %false if @work was already on a queue, %true otherwise.
  */

Re: [PATCH] workqueue: Upgrade queue_work_on() comment

[Tejun Heo]

On Tue, Nov 30, 2021 at 05:00:30PM -0800, Paul E. McKenney wrote:
> The current queue_work_on() docbook comment says that the caller must
> ensure that the specified CPU can't go away, but does not spell out the
> consequences, which turn out to be quite mild.  Therefore expand this
> comment to explicitly say that the penalty for failing to nail down the
> specified CPU is that the workqueue handler might find itself executing
> on some other CPU.
> 
> Cc: Tejun Heo <tj@kernel.org>
> Cc: Lai Jiangshan <jiangshanlai@gmail.com>
> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

Applied to wq/for-5.16-fixes.

Thanks.

-- 
tejun