Re: [PATCH v3 3/3] uio: fix crash after the device is unregistered

[Xiubo Li]

On 2018/7/10 0:40, Mike Christie wrote:
> On 07/06/2018 08:47 PM, Xiubo Li wrote:
> > On 2018/7/7 2:58, Mike Christie wrote:
> > > On 07/05/2018 09:57 PM, xiubli@xxxxxxxxxx wrote:
> > > >    void uio_event_notify(struct uio_info *info)
> > > >    {
> > > > -    struct uio_device *idev = info->uio_dev;
> > > > +    struct uio_device *idev;
> > > > +
> > > > +    if (!info)
> > > > +        return;
> > > > +
> > > > +    idev = info->uio_dev;
> > > >    
> > > For this one too, I am not sure if it is needed.
> > >
> > > uio_interrupt -> uio_event_notify. See other mail.
> > >
> > > driver XYZ -> uio_event_notify. I think drivers need to handle this and
> > > set some bits and/or perform some cleanup to make sure they are not
> > > calling uio_event_notify after it has called uio_unregister_device. The
> > > problem with the above test is if they do not they could have called
> > > uio_unregister_device right after the info test so you could still hit
> > > the problem.
> > When we are tcmu_destroy_device(), if the netlink notify event to
> > userspace is not successful then the TCMU will call the uio unregister,
> > which will set the idev->info = NULL, without close and deleting the
> > device in userspace. But the TCMU could still queue cmds to the ring
> > buffer, then the uio_event_notify will be called.
> Before tcmu_destroy_device is called LIO will have stopped new IO and
> waited for outstanding IO to be completed, so it would never be called
> after uio_unregister_device. If it does, it's a bug in LIO.
Yeah, So this should be fixed now. Only hit one crash seem related to 
uio of this code with lower kernel before.

Thanks,
BRs