2 files changed, 9 insertions, 17 deletions
diff --git a/cpukit/score/include/rtems/score/cpustdatomic.h b/cpukit/score/include/rtems/score/cpustdatomic.h
index 222ad78852..a663a06293 100644
--- a/cpukit/score/include/rtems/score/cpustdatomic.h
+++ b/cpukit/score/include/rtems/score/cpustdatomic.h
@@ -54,23 +54,13 @@ typedef atomic_uintptr_t Atomic_Pointer;
 typedef atomic_flag Atomic_Flag;
 
 /**
- * @brief the enumeration Atomic_Memory_barrier specifies the detailed regular
- * memory synchronization operations used in the atomic operation API
- * definitions.
+ * @brief Memory order according to ISO/IEC 9899:2011.
  */
 typedef enum {
-  /** no operation orders memory. */
   ATOMIC_ORDER_RELAXED = memory_order_relaxed,
-  /** a load operation performs an acquire operation on the affected memory
-  * location. This flag guarantees that the effects of load operation are
-  * completed before the effects of any later data accesses.
-  */
   ATOMIC_ORDER_ACQUIRE = memory_order_acquire,
-  /** a store operation performs a release operation on the affected memory
-  * location. This flag guarantee that all effects of all previous data
-  * accesses are completed before the store operation takes place.
-  */
-  ATOMIC_ORDER_RELEASE = memory_order_release
+  ATOMIC_ORDER_RELEASE = memory_order_release,
+  ATOMIC_ORDER_SEQ_CST = memory_order_seq_cst
 } Atomic_Order;
 
 
diff --git a/cpukit/score/include/rtems/score/schedulersmpimpl.h b/cpukit/score/include/rtems/score/schedulersmpimpl.h
index 61fbff534f..20c5d17ee7 100644
--- a/cpukit/score/include/rtems/score/schedulersmpimpl.h
+++ b/cpukit/score/include/rtems/score/schedulersmpimpl.h
@@ -92,12 +92,14 @@ static inline void _Scheduler_SMP_Allocate_processor(
 
     _Thread_Set_CPU( heir, cpu_of_victim );
 
+    cpu_of_victim->heir = heir;
+
     /*
-     * FIXME: Here we need atomic store operations with a relaxed memory order.
-     * The _CPU_SMP_Send_interrupt() will ensure that the change can be
-     * observed consistently.
+     * It is critical that we first update the heir and then the dispatch
+     * necessary so that _Thread_Dispatch() cannot miss an update.
      */
-    cpu_of_victim->heir = heir;
+    _Atomic_Fence( ATOMIC_ORDER_RELEASE );
+
     cpu_of_victim->dispatch_necessary = true;
 
     if ( cpu_of_victim != cpu_of_executing ) {