Re: [PATCH v5 3/5] USB: EHCI: improve ehci_endpoint_disable

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On Fri, Jul 26, 2013 at 04:52:36AM +0800, Ming Lei wrote:
> Hi Greg,
> 
> On Fri, Jul 26, 2013 at 3:48 AM, Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> wrote:
> > On Thu, 25 Jul 2013, Greg Kroah-Hartman wrote:
> >
> >> On Wed, Jul 03, 2013 at 10:53:09PM +0800, Ming Lei wrote:
> >> > The patch does the below improvement:
> >> >
> >> > - think QH_STATE_COMPLETING as unlinking state since all URBs on the
> >> > endpoint should be in unlinking or unlinked when doing endpoint_disable()
> >> >
> >> > - add "WARN_ON(!list_empty(&qh->qtd_list));" if qh->qh_state is
> >> > QH_STATE_LINKED because there shouldn't be any active transfer in qh
> >>
> >> If this can "never" happen, why spit a nasty message out to the error
> >> log?  What can a user do with this?
> >
> > In this context, "never" means the only way it can happen is if there's
> > a serious bug in the way usbcore handles altsetting and config changes.
> > That code is sufficiently complicated that a little extra error
> > checking won't hurt, IMO.
> >
> > If it ever happens, a user could post the log message on the mailing
> > list, giving us a chance to find and fix the bug.
> >
> >> I really don't like adding stuff like this to the kernel if at all
> >> possible.
> >
> > Up to you.  Still, I think bringing situations like this to people's
> > attention is a large part of what WARN_ON is intended for.
> 
> Yes, I agree with Alan's comment.
> 
> Could you merge this patchset since I have some following work
> which depends on this set?  Or please let me know if resend is needed.

Give me some time, this isn't trivial stuff, and I'm not quite sure I
agree that it should even be done yet...

thanks,

greg k-h
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