ALSA: Fix an error where restarting a device can fail.

miniaudio.h

@@ -28024,6 +28024,12 @@ static ma_result ma_device_start__alsa(ma_device* pDevice)
 
 static ma_result ma_device_stop__alsa(ma_device* pDevice)
 {
+    /*
+    The stop callback will get called on the worker thread after read/write__alsa() has returned. At this point there is
+    a small chance that our wakeupfd has not been cleared. We'll clear that out now if applicable.
+    */
+    int resultPoll;
+
     if (pDevice->type == ma_device_type_capture || pDevice->type == ma_device_type_duplex) {
         ma_log_postf(ma_device_get_log(pDevice), MA_LOG_LEVEL_DEBUG, "[ALSA] Dropping capture device...\n");
         ((ma_snd_pcm_drop_proc)pDevice->pContext->alsa.snd_pcm_drop)((ma_snd_pcm_t*)pDevice->alsa.pPCMCapture);
@@ -28036,6 +28042,13 @@ static ma_result ma_device_stop__alsa(ma_device* pDevice)
         } else {
             ma_log_postf(ma_device_get_log(pDevice), MA_LOG_LEVEL_DEBUG, "[ALSA] Preparing capture device successful.\n");
         }
+
+	/* Clear the wakeupfd. */
+	resultPoll = poll((struct pollfd*)pDevice->alsa.pPollDescriptorsCapture, 1, 0);
+	if (resultPoll > 0) {
+	    ma_uint64 t;
+	    read(((struct pollfd*)pDevice->alsa.pPollDescriptorsCapture)[0].fd, &t, sizeof(t));
+	}
     }
 
     if (pDevice->type == ma_device_type_playback || pDevice->type == ma_device_type_duplex) {
@@ -28050,6 +28063,14 @@ static ma_result ma_device_stop__alsa(ma_device* pDevice)
         } else {
             ma_log_postf(ma_device_get_log(pDevice), MA_LOG_LEVEL_DEBUG, "[ALSA] Preparing playback device successful.\n");
         }
+
+        /* Clear the wakeupfd. */
+	resultPoll = poll((struct pollfd*)pDevice->alsa.pPollDescriptorsPlayback, 1, 0);
+	if (resultPoll > 0) {
+	    ma_uint64 t;
+	    read(((struct pollfd*)pDevice->alsa.pPollDescriptorsPlayback)[0].fd, &t, sizeof(t));
+	}
+
     }
 
     return MA_SUCCESS;
@@ -28062,7 +28083,7 @@ static ma_result ma_device_wait__alsa(ma_device* pDevice, ma_snd_pcm_t* pPCM, st
         int resultALSA;
         int resultPoll = poll(pPollDescriptors, pollDescriptorCount, -1);
         if (resultPoll < 0) {
-            ma_log_post(ma_device_get_log(pDevice), MA_LOG_LEVEL_ERROR, "[ALSA] poll() failed.");
+            ma_log_post(ma_device_get_log(pDevice), MA_LOG_LEVEL_ERROR, "[ALSA] poll() failed.\n");
             return ma_result_from_errno(errno);
         }
 
@@ -28075,7 +28096,7 @@ static ma_result ma_device_wait__alsa(ma_device* pDevice, ma_snd_pcm_t* pPCM, st
             ma_uint64 t;
             int resultRead = read(pPollDescriptors[0].fd, &t, sizeof(t));    /* <-- Important that we read here so that the next write() does not block. */
             if (resultRead < 0) {
-                ma_log_post(ma_device_get_log(pDevice), MA_LOG_LEVEL_ERROR, "[ALSA] read() failed.");
+                ma_log_post(ma_device_get_log(pDevice), MA_LOG_LEVEL_ERROR, "[ALSA] read() failed.\n");
                 return ma_result_from_errno(errno);
             }
 
@@ -28089,13 +28110,17 @@ static ma_result ma_device_wait__alsa(ma_device* pDevice, ma_snd_pcm_t* pPCM, st
         */
         resultALSA = ((ma_snd_pcm_poll_descriptors_revents_proc)pDevice->pContext->alsa.snd_pcm_poll_descriptors_revents)(pPCM, pPollDescriptors + 1, pollDescriptorCount - 1, &revents);   /* +1, -1 to ignore the wakeup descriptor. */
         if (resultALSA < 0) {
-            ma_log_post(ma_device_get_log(pDevice), MA_LOG_LEVEL_ERROR, "[ALSA] snd_pcm_poll_descriptors_revents() failed.");
+            ma_log_post(ma_device_get_log(pDevice), MA_LOG_LEVEL_ERROR, "[ALSA] snd_pcm_poll_descriptors_revents() failed.\n");
             return ma_result_from_errno(-resultALSA);
         }
 
         if ((revents & POLLERR) != 0) {
-            ma_log_post(ma_device_get_log(pDevice), MA_LOG_LEVEL_ERROR, "[ALSA] POLLERR detected.");
-            return ma_result_from_errno(errno);
+            ma_snd_pcm_state_t state = ((ma_snd_pcm_state_proc)pDevice->pContext->alsa.snd_pcm_state)(pPCM);
+            if (state == MA_SND_PCM_STATE_XRUN) {
+                /* The PCM is in a xrun state. This will be recovered from at a higher level. We can disregard this. */
+	    } else {		    
+                ma_log_postf(ma_device_get_log(pDevice), MA_LOG_LEVEL_WARNING, "[ALSA] POLLERR detected. status = %d\n", ((ma_snd_pcm_state_proc)pDevice->pContext->alsa.snd_pcm_state)(pPCM));
+            }
         }
 
         if ((revents & requiredEvent) == requiredEvent) {