From 71e1863e7634994cc1fdc292929a002957a89fbd Mon Sep 17 00:00:00 2001
From: Michael Hanselmann <hansmi@google.com>
Date: Wed, 13 Jan 2010 11:10:17 +0100
Subject: [PATCH] locking: Fix race condition in LockSet
This patch fixes a race condition when acquiring all locks in
a LockSet instance. The list of lock names needs to be sorted
to guarantee a consistent locking order, but the names were not
sorted when acquiring all locks in the set.
Signed-off-by: Michael Hanselmann <hansmi@google.com>
Reviewed-by: Iustin Pop <iustin@google.com>
---
lib/locking.py | 7 +++----
1 file changed, 3 insertions(+), 4 deletions(-)
diff --git a/lib/locking.py b/lib/locking.py
index b738ed64d..f30e8b703 100644
--- a/lib/locking.py
+++ b/lib/locking.py
@@ -841,8 +841,6 @@ class LockSet:
# Support passing in a single resource to acquire rather than many
if isinstance(names, basestring):
names = [names]
- else:
- names = sorted(names)
return self.__acquire_inner(names, False, shared,
running_timeout.Remaining, test_notify)
@@ -891,8 +889,9 @@ class LockSet:
# First we look the locks up on __lockdict. We have no way of being sure
# they will still be there after, but this makes it a lot faster should
- # just one of them be the already wrong
- for lname in utils.UniqueSequence(names):
+ # just one of them be the already wrong. Using a sorted sequence to prevent
+ # deadlocks.
+ for lname in sorted(utils.UniqueSequence(names)):
try:
lock = self.__lockdict[lname] # raises KeyError if lock is not there
except KeyError:
--
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