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SubjectRe: [PATCH 1/1] vhost: Provide a kernel warning if mutex is held whilst clean-up in progress
On Thu, Mar 03, 2022 at 03:19:29PM +0000, Lee Jones wrote:
> All workers/users should be halted before any clean-up should take place.
>
> Suggested-by: Michael S. Tsirkin <mst@redhat.com>
> Signed-off-by: Lee Jones <lee.jones@linaro.org>
> ---
> drivers/vhost/vhost.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
> index bbaff6a5e21b8..d935d2506963f 100644
> --- a/drivers/vhost/vhost.c
> +++ b/drivers/vhost/vhost.c
> @@ -693,6 +693,9 @@ void vhost_dev_cleanup(struct vhost_dev *dev)
> int i;
>
> for (i = 0; i < dev->nvqs; ++i) {
> + /* Ideally all workers should be stopped prior to clean-up */
> + WARN_ON(mutex_is_locked(&dev->vqs[i]->mutex));
> +
> mutex_lock(&dev->vqs[i]->mutex);

I know nothing about vhost, but this construction and patch looks
strange to me.

If all workers were stopped, you won't need mutex_lock(). The mutex_lock
here suggests to me that workers can still run here.

Thanks

> if (dev->vqs[i]->error_ctx)
> eventfd_ctx_put(dev->vqs[i]->error_ctx);
> --
> 2.35.1.574.g5d30c73bfb-goog
>

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