Re: [PATCH 1/1] vhost: Provide a kernel warning if mutex is held whilst clean-up in progress

[Lee Jones]

On Thu, 03 Mar 2022, Leon Romanovsky wrote:

> 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@xxxxxxxxxx>
> > Signed-off-by: Lee Jones <lee.jones@xxxxxxxxxx>
> > ---
> >  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.

The suggestion for this patch came from the maintainer.

Please see the conversation here:

https://lore.kernel.org/all/20220302082021-mutt-send-email-mst@xxxxxxxxxx/

-- 
Lee Jones [李琼斯]
Principal Technical Lead - Developer Services
Linaro.org │ Open source software for Arm SoCs
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