--- a
+++ b/src/mediaserver/cdplugins/uprcl/rwlock.py
@@ -0,0 +1,42 @@
+# Python Cookbook by David Ascher, Alex Martelli. Credit: Sami Hangaslammi
+
+import threading
+
+class ReadWriteLock:
+    """ A lock object that allows many simultaneous "read locks", but
+    only one "write lock." """
+
+    def __init__(self):
+        self._read_ready = threading.Condition(threading.Lock(  ))
+        self._readers = 0
+
+    def acquire_read(self):
+        """ Acquire a read lock. Blocks only if a thread has
+        acquired the write lock. """
+        self._read_ready.acquire(  )
+        try:
+            self._readers += 1
+        finally:
+            self._read_ready.release(  )
+
+    def release_read(self):
+        """ Release a read lock. """
+        self._read_ready.acquire(  )
+        try:
+            self._readers -= 1
+            if not self._readers:
+                self._read_ready.notifyAll(  )
+        finally:
+            self._read_ready.release(  )
+
+    def acquire_write(self):
+        """ Acquire a write lock. Blocks until there are no
+        acquired read or write locks. """
+        self._read_ready.acquire(  )
+        while self._readers > 0:
+            self._read_ready.wait(  )
+
+    def release_write(self):
+        """ Release a write lock. """
+        self._read_ready.release(  )
+