alsa: use blocking instead of non-blocking write

The way we used non-blocking mode was HORRIBLE. It was non-blocking to ALSA, but we end up blocking in a busy loop that does absolutely NOTHING but retry. We don't check for playback cancellation (like we do in decoders) or anything. This is seriously broken and I can imagine it affects people on fast CPUs more because we do asynchronous output buffering and our ALSA device will always have data ready.

alsa: use blocking instead of non-blocking write
5c81b716 · Eric Wong · Max Kellermann · 37489b1f · 5c81b716
Commit 5c81b716 authored Sep 09, 2008 by Eric Wong Committed by Max Kellermann Sep 09, 2008
Hide whitespace changes
Inline Side-by-side

Showing with 6 additions and 1 deletion

audioOutput_alsa.c src/audioOutputs/audioOutput_alsa.c +6 -1

No files found.
--- a/src/audioOutputs/audioOutput_alsa.c
+++ b/src/audioOutputs/audioOutput_alsa.c
@@ -37,6 +37,9 @@ static const char default_device[] = "default";

 #include <alsa/asoundlib.h>

+/* #define MPD_SND_PCM_NONBLOCK SND_PCM_NONBLOCK */
+#define MPD_SND_PCM_NONBLOCK 0
+
 typedef snd_pcm_sframes_t alsa_writei_t(snd_pcm_t * pcm, const void *buffer,
 					snd_pcm_uframes_t size);

@@ -157,16 +160,18 @@ static int alsa_openDevice(struct audio_output *audioOutput)
 		      ad->device, audioFormat->bits);

 	err = snd_pcm_open(&ad->pcmHandle, ad->device,
-			   SND_PCM_STREAM_PLAYBACK, SND_PCM_NONBLOCK);
+			   SND_PCM_STREAM_PLAYBACK, MPD_SND_PCM_NONBLOCK);
 	if (err < 0) {
 		ad->pcmHandle = NULL;
 		goto error;
 	}

+#if MPD_SND_PCM_NONBLOCK == SND_PCM_NONBLOCK
 	cmd = "snd_pcm_nonblock";
 	err = snd_pcm_nonblock(ad->pcmHandle, 0);
 	if (err < 0)
 		goto error;
+#endif /* MPD_SND_PCM_NONBLOCK == SND_PCM_NONBLOCK */

 	period_time_ro = period_time = ad->period_time;
 configure_hw: