diff --git a/docs/devel/multi-thread-tcg.txt b/docs/devel/multi-thread-tcg.txt
index a99b456..faf8918 100644
--- a/docs/devel/multi-thread-tcg.txt
+++ b/docs/devel/multi-thread-tcg.txt
@@ -134,8 +134,8 @@
 searching for linked pages are done under the protect of the
 tb_lock().
 
-The global page table is protected by the tb_lock() in system-mode and
-mmap_lock() in linux-user mode.
+The global page table is a lockless radix tree; cmpxchg is used
+to atomically insert new elements.
 
 The lookup caches are updated atomically and the lookup hash uses QHT
 which is designed for concurrent safe lookup.