linux-kernel - Re: [PATCH v4 5/8] vhost: Add kthread support in function vhost_worker

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Message-ID: <e2wooukn372tdfx374ffs54cotb3y3cy3jn7gn34u4ztnnrxw5@eio7rllodou2>
Date: Tue, 10 Dec 2024 18:54:18 +0100
From: Stefano Garzarella <sgarzare@...hat.com>
To: Cindy Lu <lulu@...hat.com>
Cc: jasowang@...hat.com, mst@...hat.com, michael.christie@...cle.com, 
	linux-kernel@...r.kernel.org, virtualization@...ts.linux-foundation.org, 
	netdev@...r.kernel.org
Subject: Re: [PATCH v4 5/8] vhost: Add kthread support in function
 vhost_worker_queue()

On Wed, Dec 11, 2024 at 12:41:44AM +0800, Cindy Lu wrote:
>The function vhost_worker_queue() uses a function pointer in
>vhost_worker, which is initialized based on the inherit_owner
>value.
>
>Signed-off-by: Cindy Lu <lulu@...hat.com>
>---
> drivers/vhost/vhost.c | 5 ++++-
> 1 file changed, 4 insertions(+), 1 deletion(-)
>
>diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
>index 0175bbf4d8b3..d1aec41bcd56 100644
>--- a/drivers/vhost/vhost.c
>+++ b/drivers/vhost/vhost.c
>@@ -237,13 +237,16 @@ EXPORT_SYMBOL_GPL(vhost_poll_stop);
> static void vhost_worker_queue(struct vhost_worker *worker,
> 			       struct vhost_work *work)
> {
>+	if (!worker)
>+		return;
>+

In which scenario can `worker` be NULL?

I would like to better understand why it couldn't happen before and now 
it can.

Thanks,
Stefano

> 	if (!test_and_set_bit(VHOST_WORK_QUEUED, &work->flags)) {
> 		/* We can only add the work to the list after we're
> 		 * sure it was not in the list.
> 		 * test_and_set_bit() implies a memory barrier.
> 		 */
> 		llist_add(&work->node, &worker->work_list);
>-		vhost_task_wake(worker->vtsk);
>+		worker->task_wakeup(worker);
> 	}
> }
>
>-- 
>2.45.0
>