ALSA: snd-usb-caiaq: Missing lock around use of buffer positions

Fix a race which causes snd_pcm_update_hw_ptr_pos() to report a bug.

Signed-off-by: Mark Hills <mark@pogo.org.uk>
Acked-by: Daniel Mack <daniel@caiaq.de>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

diff --git a/sound/usb/caiaq/audio.c b/sound/usb/caiaq/audio.c
index 121af0644fd9bc901fbbc62cb676738e9049e0c7..e76017cd5acf1bee8f5d1195864df68a1144e15b 100644 (file)
--- a/sound/usb/caiaq/audio.c
+++ b/sound/usb/caiaq/audio.c
@@ -269,16 +269,22 @@ snd_usb_caiaq_pcm_pointer(struct snd_pcm_substream *sub)
 {
        int index = sub->number;
        struct snd_usb_caiaqdev *dev = snd_pcm_substream_chip(sub);
+       snd_pcm_uframes_t ptr;
+
+       spin_lock(&dev->spinlock);
 
        if (dev->input_panic || dev->output_panic)
-               return SNDRV_PCM_POS_XRUN;
+               ptr = SNDRV_PCM_POS_XRUN;
 
        if (sub->stream == SNDRV_PCM_STREAM_PLAYBACK)
-               return bytes_to_frames(sub->runtime,
+               ptr = bytes_to_frames(sub->runtime,
                                        dev->audio_out_buf_pos[index]);
        else
-               return bytes_to_frames(sub->runtime,
+               ptr = bytes_to_frames(sub->runtime,
                                        dev->audio_in_buf_pos[index]);
+
+       spin_unlock(&dev->spinlock);
+       return ptr;
 }
 
 /* operators for both playback and capture */