From 806f380a8b448ce03671f1ce07f7dfcbdc5261e1 Mon Sep 17 00:00:00 2001
From: Erik Johnston <erik@matrix.org>
Date: Wed, 15 Apr 2015 16:07:59 +0100
Subject: [PATCH] Make LruCache thread safe, as its used for event cache

---
 synapse/util/lrucache.py | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/synapse/util/lrucache.py b/synapse/util/lrucache.py
index 2f7b615f7..96163c90f 100644
--- a/synapse/util/lrucache.py
+++ b/synapse/util/lrucache.py
@@ -14,6 +14,10 @@
 # limitations under the License.
 
 
+from functools import wraps
+import threading
+
+
 class LruCache(object):
     """Least-recently-used cache."""
     # TODO(mjark) Add mutex for linked list for thread safety.
@@ -24,6 +28,16 @@ class LruCache(object):
 
         PREV, NEXT, KEY, VALUE = 0, 1, 2, 3
 
+        lock = threading.Lock()
+
+        def synchronized(f):
+            @wraps(f)
+            def inner(*args, **kwargs):
+                with lock:
+                    return f(*args, **kwargs)
+
+            return inner
+
         def add_node(key, value):
             prev_node = list_root
             next_node = prev_node[NEXT]
@@ -51,6 +65,7 @@ class LruCache(object):
             next_node[PREV] = prev_node
             cache.pop(node[KEY], None)
 
+        @synchronized
         def cache_get(key, default=None):
             node = cache.get(key, None)
             if node is not None:
@@ -59,6 +74,7 @@ class LruCache(object):
             else:
                 return default
 
+        @synchronized
         def cache_set(key, value):
             node = cache.get(key, None)
             if node is not None:
@@ -69,6 +85,7 @@ class LruCache(object):
                 if len(cache) > max_size:
                     delete_node(list_root[PREV])
 
+        @synchronized
         def cache_set_default(key, value):
             node = cache.get(key, None)
             if node is not None:
@@ -79,6 +96,7 @@ class LruCache(object):
                     delete_node(list_root[PREV])
                 return value
 
+        @synchronized
         def cache_pop(key, default=None):
             node = cache.get(key, None)
             if node:
@@ -87,9 +105,11 @@ class LruCache(object):
             else:
                 return default
 
+        @synchronized
         def cache_len():
             return len(cache)
 
+        @synchronized
         def cache_contains(key):
             return key in cache