Ticket #8616: session_file_read_write_locking.diff

django/contrib/sessions/backends/file.py

@@ -44 +44 @@
     def load(self):
         session_data = {}
         try:
-            session_file = open(self._key_to_file(), "rb")
+            flags = os.O_RDONLY | getattr(os, 'O_BINARY', 0)
+
+            # Use atomic file locking if available
+            flags |= getattr(os, 'O_SHLOCK', 0)
+
+            fd = os.open(self._key_to_file(), flags)
+            session_file = os.fdopen(fd, "rb")
             try:
                 try:
                     session_data = self.decode(session_file.read())
@@ -52 +58 @@
                     self.create()
             finally:
                 session_file.close()
-        except IOError:
+        except (OSError, IOError):
             pass
         return session_data
 
@@ -71 +77 @@
         flags = os.O_WRONLY | os.O_CREAT | os.O_TRUNC | getattr(os, 'O_BINARY', 0)
         if must_create:
             flags |= os.O_EXCL
+
+        # Use atomic file locking if available
+        flags |= getattr(os, 'O_EXLOCK', 0)
+
         # Because this may trigger a load from storage, we must do it before
         # truncating the file to save.
         session_data = self._get_session(no_load=must_create)