Handle a possible race condition
diff --git a/Lib/functools.py b/Lib/functools.py
index e4458f4..8206c4a 100644
--- a/Lib/functools.py
+++ b/Lib/functools.py
@@ -241,6 +241,12 @@
return result
result = user_function(*args, **kwds)
with lock:
+ if key in cache:
+ # getting here means that this same key was added to the
+ # cache while the lock was released. since the link
+ # update is already done, we need only return the
+ # computed result and update the count of misses.
+ pass
if currsize < maxsize:
# put result in a new link at the front of the queue
last = root[PREV]