pipeline: give Mutex and ReMutex more Pythonic semantics

This allows using mutices in with-blocks and wraps up the functionality of acquire() and try_acquire() into a single acquire(blocking=True).

Furthermore, the GIL is no longer released in cases of no contention.

tests/pipeline/test_condition_var.py

@@ -26,13 +26,12 @@ def test_cvar_notify_locked():
     m = Mutex()
     cv = ConditionVarFull(m)
 
-    m.acquire()
-    cv.notify()
-    m.release()
+    with m:
+        cv.notify()
+
+    with m:
+        cv.notify_all()
 
-    m.acquire()
-    cv.notify_all()
-    m.release()
     del cv
 
 

tests/pipeline/test_mutex.py

@@ -2,6 +2,7 @@ from panda3d.core import Mutex, ReMutex
 from panda3d import core
 from random import random
 import pytest
+import sys
 
 
 def test_mutex_acquire_release():
@@ -34,6 +35,19 @@ def test_mutex_try_acquire():
     m.release()
 
 
+def test_mutex_with():
+    m = Mutex()
+
+    rc = sys.getrefcount(m)
+    with m:
+        assert m.debug_is_locked()
+
+    with m:
+        assert m.debug_is_locked()
+
+    assert rc == sys.getrefcount(m)
+
+
 @pytest.mark.skipif(not core.Thread.is_threading_supported(),
                     reason="Threading support disabled")
 def test_mutex_contention():
@@ -124,3 +138,15 @@ def test_remutex_try_acquire():
     m.release()
     m.release()
 
+
+def test_remutex_with():
+    m = ReMutex()
+
+    rc = sys.getrefcount(m)
+    with m:
+        assert m.debug_is_locked()
+        with m:
+            assert m.debug_is_locked()
+        assert m.debug_is_locked()
+
+    assert rc == sys.getrefcount(m)