Re: [PATCH]usx2y: prevent oops & dead keyboard on hot usb unplugging

[Takashi Iwai <tiwai@suse.de>]

At Fri, 15 Apr 2005 15:59:25 +0200 (CEST),
karsten wiese wrote:
> 
> 
> --- Lee Revell <rlrevell@joe-job.com> wrote:
> > On Thu, 2005-04-14 at 20:59 +0200, karsten wiese wrote:
> > > Hi Clemens & Takashi
> > > 
> > > Please commit the patch.
> > 
> > Is the ALSA in kernel 2.6.11 affected?  If so, this
> 
> Think so, yes. The keyboard dead effect + described oops
> has been around for quiet a long time.
> (There is a lkml mail from yesterday about an usb-cellphone
> setup,
> where the same oops + dead keyboard happens also:
> http://marc.theaimsgroup.com/?i=<20050414230621.49663f75.vsu%20()%20altlinux%20!%20ru>
> )
> There is also an alsa-bug with snd-usb-audio in the
> bugbase.
> Clemens seams not to be convinced about this aproach yet.
> maybe 'cause the comment of snd_card_free_in_thread
> explicitly states that its the one to be called for
> hotplug:
> /**
>  *  snd_card_free_in_thread - call snd_card_free() in
> thread
>  *  @card: soundcard structure
>  *
>  *  This function schedules the call of snd_card_free()
> function in a
>  *  work queue.  When all devices are released (non-busy),
> the work
>  *  is woken up and calls snd_card_free().
>  *
>  *  When a card can be disconnected at any time by hotplug
> service,
>  *  this function should be used in disconnect (or detach)
> callback
>  *  instead of calling snd_card_free() directly.
>  *  
>  *  Returns - zero otherwise a negative error code if the
> start of thread failed.
>  */
> 
> Also I remember , that snd_card_free didn't work ok when i
> used it in the first implementations of usx2y-module some 2
> years ago.
> but that was on kernel 2.4.something.......
> maybe above comment is from kernel 2.4 also and the hotplug
> system has changed ? anybody?

Might be.  To be sure, check whether the release fops is called
properly before you calling snd_card_free().


Takashi


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