3 files changed, 9 insertions, 5 deletions
diff --git a/debug_toolbar/panels/__init__.py b/debug_toolbar/panels/__init__.py
index 9586e80..e60a5e6 100644
--- a/debug_toolbar/panels/__init__.py
+++ b/debug_toolbar/panels/__init__.py
@@ -51,7 +51,7 @@ class DebugPanel(object):
         """Title showing in panel"""
         raise NotImplementedError
 
-    # Enable and disable (expensive) instrumentation
+    # Enable and disable (expensive) instrumentation, must be idempotent
 
     def enable_instrumentation(self):
         pass
diff --git a/debug_toolbar/panels/cache.py b/debug_toolbar/panels/cache.py
index a6b06ce..831eacb 100644
--- a/debug_toolbar/panels/cache.py
+++ b/debug_toolbar/panels/cache.py
@@ -202,7 +202,7 @@ class CacheDebugPanel(DebugPanel):
     def enable_instrumentation(self):
         # This isn't thread-safe because cache connections aren't thread-local
         # in Django, unlike database connections.
-        cache.cache = CacheStatTracker(cache.cache)
+        cache.cache = CacheStatTracker(original_cache)
         cache.get_cache = get_cache
 
     def disable_instrumentation(self):
diff --git a/debug_toolbar/panels/sql.py b/debug_toolbar/panels/sql.py
index 53b9f53..1ccdc47 100644
--- a/debug_toolbar/panels/sql.py
+++ b/debug_toolbar/panels/sql.py
@@ -119,12 +119,16 @@ class SQLDebugPanel(DebugPanel):
     def enable_instrumentation(self):
         # This is thread-safe because database connections are thread-local.
         for connection in connections.all():
-            old_cursor = connection.cursor
-            connection.cursor = lambda: CursorWrapper(old_cursor(), connection, self)
+            if not hasattr(connection, '_djdt_cursor'):
+                connection._djdt_cursor = connection.cursor
+                connection.cursor = lambda: CursorWrapper(
+                    connection._djdt_cursor(), connection, self)
 
     def disable_instrumentation(self):
         for connection in connections.all():
-            del connection.cursor
+            if hasattr(connection, '_djdt_cursor'):
+                del connection._djdt_cursor
+                del connection.cursor
 
     def process_response(self, request, response):
         if self._queries: