Prevent the audio periodic thread from blocking the main thread.

It seems like when an android phone goes to sleep, it's possible
for something in the audio thread to block. That was causing the
audio periodic thread to block, and since the recent changes, the
main thread as well.

Now, we use a separate condition to tell the periodic thread to
run, so if the periodic thread is blocked, the main thread will
always make progress.

This probably also can improve performance of the main thread
in some rare cases.

Fixes #1301.

renpy/__init__.py

@@ -188,6 +188,7 @@ class OSVERSIONINFOEXW(ctypes.Structure):
     "renpy.loader.auto_lock",
     "renpy.display.screen.cprof",
     "renpy.audio.audio.lock",
+    "renpy.audio.audio.periodic_condition",
     }
 
 

renpy/audio/audio.py

@@ -139,7 +139,7 @@ def copy(self):
 next_channel_number = 0
 
 # the lock that mediates between the periodic and main threads.
-lock = threading.Condition()
+lock = threading.RLock()
 
 
 class Channel(object):
@@ -818,7 +818,7 @@ def init():
         renpy.game.preferences.volumes.setdefault(m, default_volume)
         renpy.game.preferences.mute.setdefault(m, False)
 
-    with lock:
+    with periodic_condition:
 
         periodic_thread_quit = False
 
@@ -835,10 +835,11 @@ def quit():  # @ReservedAssignment
     global pcm_ok
     global mix_ok
 
-    with lock:
+    with periodic_condition:
+
         if periodic_thread is not None:
             periodic_thread_quit = True
-            lock.notify()
+            periodic_condition.notify()
 
             periodic_thread.join()
 
@@ -943,21 +944,34 @@ def periodic_pass():
             raise
 
 
+# The exception that's been thrown by the periodic thread.
 periodic_exc = None
 
 
-def periodic_thread_main():
+# Should we run the periodic thread now?
+run_periodic = False
 
-    global periodic_exc
+# The condition the perodic thread runs on.
+periodic_condition = threading.Condition()
 
-    with lock:
-        while True:
 
-            lock.wait()
+def periodic_thread_main():
 
+    global periodic_exc
+    global run_periodic
+
+    while True:
+        with periodic_condition:
             if periodic_thread_quit:
                 return
 
+            if not run_periodic:
+                periodic_condition.wait()
+
+            run_periodic = False
+
+        with lock:
+
             try:
                 periodic_pass()
             except Exception:
@@ -966,12 +980,13 @@ def periodic_thread_main():
 
 def periodic():
     global periodic_exc
+    global run_periodic
 
     if not renpy.config.audio_periodic_thread:
         periodic_pass()
         return
 
-    with lock:
+    with periodic_condition:
 
         for c in all_channels:
             c.get_context()
@@ -982,7 +997,8 @@ def periodic():
 
             raise exc[0], exc[1], exc[2]
 
-        lock.notify()
+        run_periodic = True
+        periodic_condition.notify()
 
 
 def interact():