diff --git a/openmp/runtime/src/kmp_barrier.cpp b/openmp/runtime/src/kmp_barrier.cpp
--- a/openmp/runtime/src/kmp_barrier.cpp
+++ b/openmp/runtime/src/kmp_barrier.cpp
@@ -589,6 +589,7 @@
       // Wait for child to arrive
       kmp_flag_64 c_flag(&child_bar->b_arrived, new_state);
       c_flag.wait(this_thr, FALSE USE_ITT_BUILD_ARG(itt_sync_obj));
+      KMP_MB(); // Synchronize writes to child_thr.
       ANNOTATE_BARRIER_END(child_thr);
 #if USE_ITT_BUILD && USE_ITT_NOTIFY
       // Barrier imbalance - write min of the thread time and a child time to