coreaudio: always stop audio playback on shut down

Always stop audio playback and remove the playback callback when
QEMU exits.

On shut down the function coreaudio_fini_out() destroys the
coreaudio mutex but fails to stop audio playback and to remove the
audio playback callback, because function audio_is_cleaning_up()
always returns true when called from coreaudio_fini_out(). Now
there is a time window from pthread_mutex_destroy() to program
exit where Core Audio may call the audio playback callback which
tries to lock the destroyed coreaudio mutex. This leads to the
following error.

coreaudio: Could not lock voice for audioDeviceIOProc
Reason: Invalid argument

This bug was reported on the qemu-discuss mailing list.
https://lists.nongnu.org/archive/html/qemu-discuss/2020-10/msg00018.html

Tested-by: Howard Spoelstra <hsp.cat7@gmail.com>
Signed-off-by: Volker Rümelin <vr_qemu@t-online.de>
Message-id: 20201213130528.5863-3-vr_qemu@t-online.de
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>

audio/coreaudio.c

@@ -593,22 +593,20 @@ static void coreaudio_fini_out (HWVoiceOut *hw)
     int err;
     coreaudioVoiceOut *core = (coreaudioVoiceOut *) hw;
 
-    if (!audio_is_cleaning_up()) {
-        /* stop playback */
-        if (isPlaying(core->outputDeviceID)) {
-            status = AudioDeviceStop(core->outputDeviceID, core->ioprocid);
-            if (status != kAudioHardwareNoError) {
-                coreaudio_logerr (status, "Could not stop playback\n");
-            }
-        }
-
-        /* remove callback */
-        status = AudioDeviceDestroyIOProcID(core->outputDeviceID,
-                                            core->ioprocid);
+    /* stop playback */
+    if (isPlaying(core->outputDeviceID)) {
+        status = AudioDeviceStop(core->outputDeviceID, core->ioprocid);
         if (status != kAudioHardwareNoError) {
-            coreaudio_logerr (status, "Could not remove IOProc\n");
+            coreaudio_logerr(status, "Could not stop playback\n");
         }
     }
+
+    /* remove callback */
+    status = AudioDeviceDestroyIOProcID(core->outputDeviceID,
+                                        core->ioprocid);
+    if (status != kAudioHardwareNoError) {
+        coreaudio_logerr(status, "Could not remove IOProc\n");
+    }
     core->outputDeviceID = kAudioDeviceUnknown;
 
     /* destroy mutex */
@@ -633,13 +631,11 @@ static void coreaudio_enable_out(HWVoiceOut *hw, bool enable)
         }
     } else {
         /* stop playback */
-        if (!audio_is_cleaning_up()) {
-            if (isPlaying(core->outputDeviceID)) {
-                status = AudioDeviceStop(core->outputDeviceID,
-                                         core->ioprocid);
-                if (status != kAudioHardwareNoError) {
-                    coreaudio_logerr (status, "Could not pause playback\n");
-                }
+        if (isPlaying(core->outputDeviceID)) {
+            status = AudioDeviceStop(core->outputDeviceID,
+                                     core->ioprocid);
+            if (status != kAudioHardwareNoError) {
+                coreaudio_logerr(status, "Could not pause playback\n");
             }
         }
     }