From 9c9f23eee90f1df49098080dee0c10c7b9883ea6 Mon Sep 17 00:00:00 2001
From: wm4 <wm4@nowhere>
Date: Fri, 30 May 2014 23:54:11 +0200
Subject: ao_alsa: reduce spurious wakeups

Apparently this can happen. So actually only return from waiting if ALSA
excplicitly signals that new output is available, or if we are woken up
externally.
---
 audio/out/ao_alsa.c | 22 ++++++++++++++--------
 audio/out/push.c    |  6 ++++--
 2 files changed, 18 insertions(+), 10 deletions(-)

diff --git a/audio/out/ao_alsa.c b/audio/out/ao_alsa.c
index 6b755a6d5c..081f9efebf 100644
--- a/audio/out/ao_alsa.c
+++ b/audio/out/ao_alsa.c
@@ -712,14 +712,20 @@ static int audio_wait(struct ao *ao, pthread_mutex_t *lock)
     err = snd_pcm_poll_descriptors(p->alsa, fds, num_fds);
     CHECK_ALSA_ERROR("cannot get pollfds");
 
-    int r = ao_wait_poll(ao, fds, num_fds, lock);
-    if (r < 0)
-        return r;
-
-    unsigned short revents;
-    snd_pcm_poll_descriptors_revents(p->alsa, fds, num_fds, &revents);
-    CHECK_ALSA_ERROR("cannot read poll events");
-
+    while (1) {
+        int r = ao_wait_poll(ao, fds, num_fds, lock);
+        if (r)
+            return r;
+
+        unsigned short revents;
+        snd_pcm_poll_descriptors_revents(p->alsa, fds, num_fds, &revents);
+        CHECK_ALSA_ERROR("cannot read poll events");
+
+        if (revents & POLLERR)
+            return -1;
+        if (revents & POLLOUT)
+            return 0;
+    }
     return 0;
 
 alsa_error:
diff --git a/audio/out/push.c b/audio/out/push.c
index 409a5f50e0..cd7b8dc329 100644
--- a/audio/out/push.c
+++ b/audio/out/push.c
@@ -410,7 +410,7 @@ int ao_play_silence(struct ao *ao, int samples)
 // Call poll() for the given fds. This will extend the given fds with the
 // wakeup pipe, so ao_wakeup_poll() will basically interrupt this function.
 // Unlocks the lock temporarily.
-// Returns <0 on error, 0 on success.
+// Returns <0 on error, 0 on success, 1 if the caller should return immediately.
 int ao_wait_poll(struct ao *ao, struct pollfd *fds, int num_fds,
                  pthread_mutex_t *lock)
 {
@@ -434,13 +434,15 @@ int ao_wait_poll(struct ao *ao, struct pollfd *fds, int num_fds,
     pthread_mutex_lock(&p->lock);
 
     memcpy(fds, p_fds, num_fds * sizeof(fds[0]));
+    bool wakeup = false;
     if (p_fds[num_fds].revents & POLLIN) {
+        wakeup = true;
         // flush the wakeup pipe contents - might "drown" some wakeups, but
         // that's ok for our use-case
         char buf[100];
         read(p->wakeup_pipe[0], buf, sizeof(buf));
     }
-    return (r >= 0 || r == -EINTR) ? 0 : -1;
+    return (r >= 0 || r == -EINTR) ? wakeup : -1;
 }
 
 void ao_wakeup_poll(struct ao *ao)
-- 
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