[alsa-devel] [PATCH 1/2] ALSA: hda - skip runtime PM if async probe is not finished

[Eoff, Ullysses A]

> -----Original Message-----
> From: alsa-devel-bounces at alsa-project.org [mailto:alsa-devel-bounces at alsa-project.org] On Behalf Of Takashi Iwai
> Sent: Monday, July 27, 2015 10:39 PM
> To: Eoff, Ullysses A
> Cc: Yang, Libin; alsa-devel at alsa-project.org; Lee, Zhuo-hao
> Subject: Re: [alsa-devel] [PATCH 1/2] ALSA: hda - skip runtime PM if async probe is not finished
> 
> On Mon, 27 Jul 2015 23:34:53 +0200,
> U. Artie Eoff wrote:
> >
> > Crash can occur if runtime PM is triggered before the async probe
> > finishes via the azx_firmware_cb when CONFIG_SND_HDA_PATCH_LOADER
> > is defined.
> >
> > Don't execute PM ops if the async probe has not completed yet.
> >
> > The probe is finished when chip->running is true.
> >
> > Signed-off-by: U. Artie Eoff <ullysses.a.eoff at intel.com>
> > ---
> >  sound/pci/hda/hda_intel.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/sound/pci/hda/hda_intel.c b/sound/pci/hda/hda_intel.c
> > index 735bdcb04ce8..b729b25a6ad6 100644
> > --- a/sound/pci/hda/hda_intel.c
> > +++ b/sound/pci/hda/hda_intel.c
> > @@ -1023,7 +1023,7 @@ static int azx_runtime_idle(struct device *dev)
> >
> >  	chip = card->private_data;
> >  	hda = container_of(chip, struct hda_intel, chip);
> > -	if (chip->disabled || hda->init_failed)
> > +	if (chip->disabled || hda->init_failed || !chip->running)
> >  		return 0;
> 
> For !chip->running, it's better to return -EBUSY.
> 
> The disabled and init_failed flags are checked in runtime_suspend()
> and runtime_resume() to skip the whole procedures, too.
> 
> And I guess the check of chip->running should suffice even without the
> second patch.  It assures that the bus is powered on.
> 

Hmm... wait a second.  I think we still need to check bus->chip_init
as in the second patch.  I just noticed that the async probe 
finishes (i.e. chip->running = 1) before chip init executes (i.e. before
bus->chip_init is set).  This allows a small window for the issue
I described in my second patch to occur.

I already sent another patch to replace these two... but I didn't
add the check for bus->chip_init in that patch.  I'll create a v2
for that but will wait for your feedback first.

> 
> thanks,
> 
> Takashi
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