On Fri, Apr 22, 2022 at 02:11:27AM +0000, Tian, Kevin wrote:

> >     mutex_lock(&device->dev_set->lock);
> > -   if (!--device->open_count && device->ops->close_device)
> > +   vfio_assert_device_open(device);
> > +   if (device->open_count == 1 && device->ops->close_device)
> >             device->ops->close_device(device);
> > +   device->open_count--;
> >     mutex_unlock(&device->dev_set->lock);
> 
> Is it necessary to add assertion here? This is the only place to
> decrement the counter and no similar assertion in other release()/
> put() functions.

Necessary, no, but since we have it we may as well check it here. It
is common to check that refcounts don't underflow.

Jason

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