1 files changed, 12 insertions, 1 deletions
diff --git a/cpukit/score/src/threaddispatch.c b/cpukit/score/src/threaddispatch.c
index 40a2efbb82..9e3f86e23b 100644
--- a/cpukit/score/src/threaddispatch.c
+++ b/cpukit/score/src/threaddispatch.c
@@ -97,9 +97,20 @@ void _Thread_Dispatch( void )
 #else
   while ( per_cpu->dispatch_necessary ) {
 #endif
-    heir = per_cpu->heir;
     per_cpu->dispatch_necessary = false;
+
+#if defined( RTEMS_SMP )
+    /*
+     * It is critical that we first update the dispatch necessary and then the
+     * read the heir so that we don't miss an update by
+     * _Scheduler_SMP_Allocate_processor().
+     */
+    _Atomic_Fence( ATOMIC_ORDER_SEQ_CST );
+#endif
+
+    heir = per_cpu->heir;
     per_cpu->executing = heir;
+
 #if defined( RTEMS_SMP )
     executing->is_executing = false;
     heir->is_executing = true;