At Thu, 11 Jul 2013 22:13:35 +0800,
Ming Lei wrote:
>
> On Thu, Jul 11, 2013 at 9:50 PM, Takashi Iwai <tiwai@xxxxxxx> wrote:
> > At Thu, 11 Jul 2013 17:08:30 +0400,
> > Sergei Shtylyov wrote:
> >>
> >> On 11-07-2013 13:06, Ming Lei wrote:
> >>
> >> > Complete() will be run with interrupt enabled, so change to
> >> > spin_lock_irqsave().
> >>
> >> Changelog doesn't match the patch.
> >
> > Yep, but moreover...
> >
> >> > Cc: Jaroslav Kysela <perex@xxxxxxxx>
> >> > Cc: Takashi Iwai <tiwai@xxxxxxx>
> >> > Cc: alsa-devel@xxxxxxxxxxxxxxxx
> >> > Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxxxxx>
> >> > ---
> >> > sound/usb/usx2y/usbusx2yaudio.c | 4 ++++
> >> > 1 file changed, 4 insertions(+)
> >>
> >> > diff --git a/sound/usb/usx2y/usbusx2yaudio.c b/sound/usb/usx2y/usbusx2yaudio.c
> >> > index 4967fe9..e2ee893 100644
> >> > --- a/sound/usb/usx2y/usbusx2yaudio.c
> >> > +++ b/sound/usb/usx2y/usbusx2yaudio.c
> >> > @@ -273,7 +273,11 @@ static void usX2Y_clients_stop(struct usX2Ydev *usX2Y)
> >> > struct snd_usX2Y_substream *subs = usX2Y->subs[s];
> >> > if (subs) {
> >> > if (atomic_read(&subs->state) >= state_PRERUNNING) {
> >> > + unsigned long flags;
> >> > +
> >> > + local_irq_save(flags);
> >> > snd_pcm_stop(subs->pcm_substream, SNDRV_PCM_STATE_XRUN);
> >> > + local_irq_restore(flags);
> >> > }
> >
> > ... actually this snd_pcm_stop() call should have been covered by
> > snd_pcm_stream_lock(). Maybe it'd be enough to have a single patch
> > together with the change, i.e. wrapping with
> > snd_pcm_stream_lock_irqsave().
>
> Please use snd_pcm_stream_lock_irqsave() so that I can avoid sending
> out similar patch later, :-)
>
> >
> > I'll prepare the patch for 3.11 independently from your patch series,
> > so please drop this one.
>
> OK, thanks for dealing with that.
>
> >
> >
> > BTW, the word "cleanup" in the subject is inappropriate. This is
> > rather a fix together with the core change.
>
> It is a cleanup since the patchset only addresses lock problem which
> is caused by the tasklet conversion.
Well, the conversion to irqsave() is needed for the future drop of
irq_save() in the caller, right? Then this isn't a cleanup but a
preparation for movement ahead.
> > And, I wonder whether we can take a safer approach. When the caller
> > condition changed, we often introduced either a different ops
> > (e.g. ioctl case) or a flag for the new condition, at least during the
> > transition period.
>
> Interrupt is't enabled until all current drivers are cleaned up, so it is really
> safe, please see patch [2].
OK.
> > Last but not least, is a conversion to tasklet really preferred?
> > tasklet is rather an obsoleted infrastructure nowadays, and people
> > don't recommend to use it any longer, AFAIK.
>
> We discussed the problem in the below link previously[1], Steven
> and Thomas suggested to use threaded irq handler, but which
> may degrade USB mass storage performance, so we have to
> take tasklet now until we rewrite transport part of USB mass storage
> driver.
>
> Also the conversion[2] has avoided the tasklet spin lock problem
> already.
OK, good to know.
thanks,
Takashi
> [1], http://marc.info/?t=137079119200001&r=1&w=2
> [2], http://marc.info/?l=linux-usb&m=137286326726326&w=2
>
> Thanks,
> --
> Ming Lei
>
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