RE: Re: Re: Re: Re: Re: [syzbot] INFO: rcu detected stall in tx

[Guido Kiener]

> On Wed, May 19, 2021 at 10:48:29AM +0200, dave penkler wrote:
> > On Sat, 8 May 2021 at 16:29, Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> wrote:
> > >
> > > On Sat, May 08, 2021 at 10:14:41AM +0200, dave penkler wrote:
> > > > When the host driver detects a protocol error while processing an
> > > > URB it completes the URB with EPROTO status and marks the endpoint
> > > > as halted.
> > >
> > > Not true.  It does not mark the endpoint as halted, not unless it
> > > receives a STALL handshake from the device.  A STALL is not a
> > > protocol error.
> > >
> > > > When the class driver resubmits the URB and the if the host driver
> > > > finds the endpoint still marked as halted it should return EPIPE
> > > > status on the resubmitted URB
> > >
> > > Irrelevant.
> > Not at all. The point is that when an application is talking to an
> > instrument over the usbtmc driver, the underlying host controller and
> > its driver will detect and silence a babbling endpoint.
> 
> No, they won't.  That is, they will detect a babble error and return an error status, but
> they won't silence the endpoint.  What makes you think they will?

Maybe there is a misunderstanding. I guess that Dave wanted to propose:
"EPROTO is a link level issue and needs to be handled by the host driver.
When the host driver detects a protocol error while processing an
URB it SHOULD complete the URB with EPROTO status and SHOULD mark the endpoint
as halted."
Is this a realistic fix for all host drivers?

-Guido