On Thu, Mar 03, 2022 at 09:14:36PM +0200, 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.
>
> Thanks
"Ideally" here is misleading, we need a bigger detailed comment
along the lines of:
/*
* By design, no workers can run here. But if there's a bug and the
* driver did not flush all work properly then they might, and we
* encountered such bugs in the past. With no proper flush guest won't
* work correctly but avoiding host memory corruption in this case
* sounds like a good idea.
*/
> > if (dev->vqs[i]->error_ctx)
> > eventfd_ctx_put(dev->vqs[i]->error_ctx);
> > --
> > 2.35.1.574.g5d30c73bfb-goog
> >
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