Re: [PATCH v6 6/9] ALSA: virtio: PCM substream operators

[Anton Yakovlev <anton.yakovlev@opensynergy.com>]

On 28.02.2021 12:32, Takashi Iwai wrote:
> On Sat, 27 Feb 2021 09:59:53 +0100,
> Anton Yakovlev wrote:
> >


[snip]


> > +static snd_pcm_uframes_t
> > +virtsnd_pcm_pointer(struct snd_pcm_substream *substream)
> > +{
> > +     struct virtio_pcm_substream *vss = snd_pcm_substream_chip(substream);
> > +     snd_pcm_uframes_t hw_ptr = SNDRV_PCM_POS_XRUN;
> > +     unsigned long flags;
> > +
> > +     spin_lock_irqsave(&vss->lock, flags);
> > +     if (!vss->xfer_xrun)
> > +             hw_ptr = bytes_to_frames(substream->runtime, vss->hw_ptr);
> > +     spin_unlock_irqrestore(&vss->lock, flags);
>
> Oh, and if we drop nonatomc PCM, both trigger and pointer callbacks
> are guaranteed to be called inside the spinlock, hence you can remove
> *_irqsave() but just us spin_lock() in those two callbacks.

As I understand, spin_lock_irqsave() disables only local interrupts. But
what about other CPU cores?


> thanks,
>
> Takashi

--
Anton Yakovlev
Senior Software Engineer

OpenSynergy GmbH
Rotherstr. 20, 10245 Berlin