Re: usb HC busted?

[Sudip Mukherjee <sudipm.mukherjee-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>]

Hi Mathias,

On Thu, Jul 19, 2018 at 01:59:01PM +0300, Mathias Nyman wrote:
> On 17.07.2018 18:10, Sudip Mukherjee wrote:
> > Hi Alan, Greg,
> > 
> > On Tue, Jul 17, 2018 at 03:49:18PM +0100, Sudip Mukherjee wrote:
> > > On Tue, Jul 17, 2018 at 03:40:22PM +0100, Sudip Mukherjee wrote:
> > > > Hi Alan,
> > > > 
> > > > On Tue, Jul 17, 2018 at 10:28:14AM -0400, Alan Stern wrote:
> > > > > On Tue, 17 Jul 2018, Sudip Mukherjee wrote:
> > > > > 
> > > > > > I did some more debugging. Tested with a KASAN enabled kernel and that
> > > > > > shows the problem. The report is attached.
> > > > > > 
<snip>
> > 
> > And, my hacky patch worked as I prevented it from calling
> > usb_disable_interface() in this particular case.
> > 
> 
> Back for a few days, looking at this

I hope you had a good holiday. :)

> 
> xhci driver will set up all the endpoints for the new altsetting already in
> usb_hcd_alloc_bandwidth().
> 
<snip>
> 
> As first aid I could try to implement checks that make sure the flushed URBs
> trb pointers really are on the current endpoint ring, and also add some warning
> if we are we are dropping endpoints with URBs still queued.

Yes, please. I think your first-aid will be a much better option than
the hacky patch I am using atm.

> 
> But we need to fix this properly as well.
> xhci needs to be more in sync with usb core in usb_set_interface(), currently xhci
> has the altssetting up and running when usb core hasn't event started flushing endpoints.

I am able to reproduce this on almost all cycles, so I can always test
the fix for you after you are fully back from your holiday.

--
Regards
Sudip