Re: [alsa-devel] [Xen-devel][PATCH 3/3] ALSA: xen-front: Use Xen common shared buffer implementation

[Oleksandr Andrushchenko]

On 11/22/18 5:47 PM, Takashi Iwai wrote:
> On Thu, 22 Nov 2018 11:02:30 +0100,
> Oleksandr Andrushchenko wrote:
> > @@ -214,12 +221,19 @@ static void stream_clear(struct xen_snd_front_pcm_stream_info *stream)
> >   	stream->out_frames = 0;
> >   	atomic_set(&stream->hw_ptr, 0);
> >   	xen_snd_front_evtchnl_pair_clear(stream->evt_pair);
> > -	xen_snd_front_shbuf_clear(&stream->sh_buf);
> > +	memset(&stream->shbuf, 0, sizeof(stream->shbuf));
> > +	stream->buffer = NULL;
> > +	stream->buffer_sz = 0;
> > +	stream->pages = NULL;
> > +	stream->num_pages = 0;
> >   }
> >   
> >   static void stream_free(struct xen_snd_front_pcm_stream_info *stream)
> >   {
> > -	xen_snd_front_shbuf_free(&stream->sh_buf);
> > +	xen_front_pgdir_shbuf_unmap(&stream->shbuf);
> > +	xen_front_pgdir_shbuf_free(&stream->shbuf);
> > +	free_pages_exact(stream->buffer, stream->buffer_sz);
> > +	kfree(stream->pages);
> >   	stream_clear(stream);
> >   }
> >   
> > @@ -421,10 +435,34 @@ static int alsa_close(struct snd_pcm_substream *substream)
> >   	return 0;
> >   }
> >   
> > +static int shbuf_setup_backstore(struct xen_snd_front_pcm_stream_info *stream,
> > +				 size_t buffer_sz)
> > +{
> > +	int i;
> > +
> > +	stream->buffer_sz = buffer_sz;
> > +	stream->buffer = alloc_pages_exact(stream->buffer_sz, GFP_KERNEL);
> > +	if (!stream->buffer)
> > +		return -ENOMEM;
> This keeps the NULL stream->buffer, and then the caller goes to the
> error path via stream_free() which will lead to an Oops due to the
> unconditional call of free_pages_exact().

You are absolutely right, will fix

Thank you for catching this

> thanks,
>
> Takashi