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

[Takashi Iwai]

On Tue, 28 Jul 2015 08:05:08 +0200,
Yang, Libin wrote:
> 
> > -----Original Message-----
> > From: Takashi Iwai [mailto:tiwai at suse.de]
> > Sent: Tuesday, July 28, 2015 1:39 PM
> > To: Eoff, Ullysses A
> > Cc: alsa-devel at alsa-project.org; Lee, Zhuo-hao; Yang, Libin
> > Subject: Re: [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.
> 
> As, in runtime_resume will call azx_init_chip(), which may sleep,
> is there any race when calling azx_runtime_resume(), 
> azx_runtime_idle is called and enter azx_runtime_suspend()?
> Or the ACPI subsystem will handle such situation?

The reentrace is avoided in the runtime PM core side, IIRC.


Takashi