[1.9.x] Fixed #26332 -- Fixed a race condition in BaseCache.get_or_set().

Backport of 96ec67a7cf89a136e793305343c5bba8521cdb47 from master

1 files changed, 5 insertions, 5 deletions

diff --git a/django/core/cache/backends/base.py b/django/core/cache/backends/base.py
index 75a131ac3a..12351c5bcd 100644
--- a/django/core/cache/backends/base.py
+++ b/django/core/cache/backends/base.py
@@ -154,8 +154,7 @@ class BaseCache(object):
         also be any callable. If timeout is given, that timeout will be used
         for the key; otherwise the default cache timeout will be used.
 
-        Returns the value of the key stored or retrieved on success,
-        False on error.
+        Return the value of the key stored or retrieved.
         """
         if default is None:
             raise ValueError('You need to specify a value.')
@@ -163,9 +162,10 @@ class BaseCache(object):
         if val is None:
             if callable(default):
                 default = default()
-            val = self.add(key, default, timeout=timeout, version=version)
-            if val:
-                return self.get(key, default, version)
+            self.add(key, default, timeout=timeout, version=version)
+            # Fetch the value again to avoid a race condition if another caller
+            # added a value between the first get() and the add() above.
+            return self.get(key, default, version=version)
         return val
 
     def has_key(self, key, version=None):