Added AcquiresAllOrNone class in utils.

ccserver/utils.py

@@ -5,6 +5,8 @@
 Some helpers used by cc-server.
 '''
 
+from threading import Lock
+
 class Acquires(object):
 
     '''
@@ -34,3 +36,28 @@ class Acquires(object):
     def __exit__(self, exc_type, exc_value, traceback):
         for lock in self._locks:
             lock.release()
+
+
+class AcquiresAllOrNone(Acquires):
+
+    '''
+    Class that extend Acquires to allow to release all lock if one of them
+    is not free.
+    '''
+
+    # Global acquire lock:
+    acquirelock = Lock()
+
+    def __enter__(self):
+        while True:
+            with self.acquirelock:
+                acquired = []
+                for lock in self._locks:
+                    if not lock.acquire(False):
+                        for lock_acquired in acquired:
+                            lock_acquired.release()
+                        break
+                    else:
+                        acquired.append(lock)
+                else:
+                    break