mmdevice: use a semaphore to signal the initial mmdevice queries are done

We don't need the lock for that.
However the semaphore will keep being signal after the initial phase as
we don't have a way in MMSession() to tell if DEVICE_PENDING means the initial
phase or a change of device.

modules/audio_output/mmdevice.c

@@ -102,6 +102,7 @@ typedef struct
     wchar_t *device_name; /**< device identifier to use, NULL if default */
     bool default_device_changed;
     HANDLE work_event;
+    vlc_sem_t init_passed;
     vlc_mutex_t lock;
     vlc_cond_t ready;
     vlc_thread_t thread; /**< Thread for audio session control */
@@ -938,6 +939,7 @@ static HRESULT MMSession(audio_output_t *aout, IMMDeviceEnumerator *it)
     }
 
     vlc_cond_signal(&sys->ready);
+    vlc_sem_post(&sys->init_passed);
 
     if (FAILED(hr))
     {
@@ -1152,10 +1154,8 @@ static void *MMThread(void *data)
     return NULL;
 
 error:
-    vlc_mutex_lock(&sys->lock);
     sys->device_status = DEVICE_INITIALISATION_FAILED;
-    vlc_cond_signal(&sys->ready);
-    vlc_mutex_unlock(&sys->lock);
+    vlc_sem_post(&sys->init_passed);
     return NULL;
 }
 
@@ -1349,6 +1349,7 @@ static int Open(vlc_object_t *obj)
     if (!var_CreateGetBool(aout, "volume-save"))
         VolumeSetLocked(aout, var_InheritFloat(aout, "mmdevice-volume"));
 
+    vlc_sem_init(&sys->init_passed, 0);
     vlc_mutex_init(&sys->lock);
     vlc_cond_init(&sys->ready);
 
@@ -1377,19 +1378,13 @@ static int Open(vlc_object_t *obj)
     if (vlc_clone(&sys->thread, MMThread, aout))
         goto error;
 
-    vlc_mutex_lock(&sys->lock);
-    while (sys->device_status == DEVICE_PENDING)
-    {
-        vlc_cond_wait(&sys->ready, &sys->lock);
+    vlc_sem_wait(&sys->init_passed);
 
-        if (sys->device_status == DEVICE_INITIALISATION_FAILED)
-        {
-            vlc_mutex_unlock(&sys->lock);
-            Close(obj);
-            return VLC_EGENERIC;
-        }
+    if (sys->device_status == DEVICE_INITIALISATION_FAILED)
+    {
+        Close(obj);
+        return VLC_EGENERIC;
     }
-    vlc_mutex_unlock(&sys->lock);
 
     aout->start = Start;
     aout->stop = Stop;