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

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