Re: Ooops when working with USB MIDI (2.6.33.1)

Clemens Ladisch
2010-04-09T07:19:39Z

Tvrtko Ursulin wrote:
> On Thursday 08 Apr 2010 13:22:36 Takashi Iwai wrote:
> > > Takashi, do you remember what the original problem was?
> >
> > Well, I have only a vague memory -- it's a similar scenario that some app
> > still accessing after disconnection. The URB can't be handled after
> > the disconnection is finished.
> >
> > I think the patch below might fix in this case. You can try it
> > instead of reverting the commit above.
> >
> > --- a/sound/usb/usbmidi.c
> > +++ b/sound/usb/usbmidi.c
> > @@ -986,6 +986,8 @@ static void snd_usbmidi_output_drain(struct
> > snd_rawmidi_substream *substream) DEFINE_WAIT(wait);
> > long timeout = msecs_to_jiffies(50);
> >
> > + if (ep->umidi->disconnected)
> > + return;
> > ...
> > @@ -1275,6 +1277,11 @@ void snd_usbmidi_disconnect(struct list_head* p)
> > snd_usbmidi_in_endpoint_delete(ep->in);
> > ep->in = NULL;
> > }
> > + ep->active_urbs = 0;
> > + if (ep->drain_urbs) {
> > + ep->drain_urbs = 0;
> > + wake_up(&ep->drain_wait);
> > + }
>
> For the second hunk, do you think ep->out->... and so on? That would be more
> in-line with code present in 2.6.33.

ep->out has been just freed. And in the first hunk, in _drain, the ep
pointer is the same as ep->out in _disconnect.

In _disconnect, we must not free ep->in and ep->out because those
structures might still be accessed by all the functions called from
user space.

I'll write separate disconnect functions for the endpoint structures
when I find time.

Regards,
Clemens