From 389890a1f095919598043380709ab1c2ee6dddfc Mon Sep 17 00:00:00 2001
From: Erik Johnston <erik@matrix.org>
Date: Thu, 13 Aug 2026 13:24:02 +0100
Subject: [PATCH] Assert the lock is locked

---
 synapse/storage/util/id_generators.py | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/synapse/storage/util/id_generators.py b/synapse/storage/util/id_generators.py
index 88f04702b4..ad524c1192 100644
--- a/synapse/storage/util/id_generators.py
+++ b/synapse/storage/util/id_generators.py
@@ -366,6 +366,8 @@ class MultiWriterIdGenerator(AbstractStreamIdGenerator):
 
         Must be called with `_lock` held.
         """
+        assert self._lock.locked()
+
         self._current_position_gauge.set(
             self._return_factor * self._persisted_upto_position
         )