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

Takashi Iwai
2018-11-22T15:47:18Z

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().

thanks,

Takashi