diff --git a/changelog.d/10993.misc b/changelog.d/10993.misc
new file mode 100644
index 000000000..23c73dbac
--- /dev/null
+++ b/changelog.d/10993.misc
@@ -0,0 +1 @@
+Fix a long-standing bug where `ReadWriteLock`s could drop logging contexts on exit.
diff --git a/synapse/util/async_helpers.py b/synapse/util/async_helpers.py
index 82d918a05..5df80ea8e 100644
--- a/synapse/util/async_helpers.py
+++ b/synapse/util/async_helpers.py
@@ -438,7 +438,8 @@ class ReadWriteLock:
             try:
                 yield
             finally:
-                new_defer.callback(None)
+                with PreserveLoggingContext():
+                    new_defer.callback(None)
                 self.key_to_current_readers.get(key, set()).discard(new_defer)
 
         return _ctx_manager()
@@ -466,7 +467,8 @@ class ReadWriteLock:
             try:
                 yield
             finally:
-                new_defer.callback(None)
+                with PreserveLoggingContext():
+                    new_defer.callback(None)
                 if self.key_to_current_writer[key] == new_defer:
                     self.key_to_current_writer.pop(key)