score: Need for help indicator for scheduler ops

Return a thread in need for help for the following scheduler operations

- unblock,
- change priority, and
- yield.

A thread in need for help is a thread that encounters a scheduler state
change from scheduled to ready or a thread that cannot be scheduled in
an unblock operation.  Such a thread can ask threads which depend on
resources owned by this thread for help.

13 files changed, 121 insertions, 76 deletions

diff --git a/cpukit/score/src/schedulercbsunblock.c b/cpukit/score/src/schedulercbsunblock.c
index 5822af2934..688253c279 100644
--- a/cpukit/score/src/schedulercbsunblock.c
+++ b/cpukit/score/src/schedulercbsunblock.c
@@ -25,7 +25,7 @@
 #include <rtems/score/threadimpl.h>
 #include <rtems/score/watchdogimpl.h>
 
-void _Scheduler_CBS_Unblock(
+Scheduler_Void_or_thread _Scheduler_CBS_Unblock(
   const Scheduler_Control *scheduler,
   Thread_Control          *the_thread
 )
@@ -84,4 +84,6 @@ void _Scheduler_CBS_Unblock(
          the_thread->current_priority == 0 )
       _Thread_Dispatch_necessary = true;
   }
+
+  SCHEDULER_RETURN_VOID_OR_NULL;
 }
diff --git a/cpukit/score/src/scheduleredfchangepriority.c b/cpukit/score/src/scheduleredfchangepriority.c
index 1422fb174e..32b0993d8f 100644
--- a/cpukit/score/src/scheduleredfchangepriority.c
+++ b/cpukit/score/src/scheduleredfchangepriority.c
@@ -20,7 +20,7 @@
 
 #include <rtems/score/scheduleredfimpl.h>
 
-void _Scheduler_EDF_Change_priority(
+Scheduler_Void_or_thread _Scheduler_EDF_Change_priority(
   const Scheduler_Control *scheduler,
   Thread_Control          *the_thread,
   Priority_Control         new_priority,
@@ -33,4 +33,6 @@ void _Scheduler_EDF_Change_priority(
 
   _RBTree_Extract( &context->Ready, &node->Node );
   _RBTree_Insert( &context->Ready, &node->Node );
+
+  SCHEDULER_RETURN_VOID_OR_NULL;
 }
diff --git a/cpukit/score/src/scheduleredfunblock.c b/cpukit/score/src/scheduleredfunblock.c
index 30fa4f0163..469655e9d2 100644
--- a/cpukit/score/src/scheduleredfunblock.c
+++ b/cpukit/score/src/scheduleredfunblock.c
@@ -22,7 +22,7 @@
 #include <rtems/score/schedulerimpl.h>
 #include <rtems/score/thread.h>
 
-void _Scheduler_EDF_Unblock(
+Scheduler_Void_or_thread _Scheduler_EDF_Unblock(
   const Scheduler_Control *scheduler,
   Thread_Control          *the_thread
 )
@@ -51,4 +51,6 @@ void _Scheduler_EDF_Unblock(
          the_thread->current_priority == 0 )
       _Thread_Dispatch_necessary = true;
   }
+
+  SCHEDULER_RETURN_VOID_OR_NULL;
 }
diff --git a/cpukit/score/src/scheduleredfyield.c b/cpukit/score/src/scheduleredfyield.c
index 0990ac0b14..5aa2afd8db 100644
--- a/cpukit/score/src/scheduleredfyield.c
+++ b/cpukit/score/src/scheduleredfyield.c
@@ -21,7 +21,7 @@
 
 #include <rtems/score/scheduleredfimpl.h>
 
-void _Scheduler_EDF_Yield(
+Scheduler_Void_or_thread _Scheduler_EDF_Yield(
   const Scheduler_Control *scheduler,
   Thread_Control          *the_thread
 )
@@ -38,4 +38,6 @@ void _Scheduler_EDF_Yield(
   _RBTree_Insert( &context->Ready, &node->Node );
 
   _Scheduler_EDF_Schedule_body( scheduler, the_thread, false );
+
+  SCHEDULER_RETURN_VOID_OR_NULL;
 }
diff --git a/cpukit/score/src/schedulerpriorityaffinitysmp.c b/cpukit/score/src/schedulerpriorityaffinitysmp.c
index e6a662e361..14a022e5d7 100644
--- a/cpukit/score/src/schedulerpriorityaffinitysmp.c
+++ b/cpukit/score/src/schedulerpriorityaffinitysmp.c
@@ -288,14 +288,16 @@ static Scheduler_Node * _Scheduler_priority_affinity_SMP_Get_lowest_scheduled(
  * _Scheduler_priority_affinity_SMP_Get_lowest_scheduled into
  * _Scheduler_SMP_Enqueue_ordered.
  */
-static void _Scheduler_priority_affinity_SMP_Enqueue_fifo(
+static Thread_Control *_Scheduler_priority_affinity_SMP_Enqueue_fifo(
   Scheduler_Context *context,
-  Scheduler_Node    *node
+  Scheduler_Node    *node,
+  Thread_Control    *needs_help
 )
 {
-  _Scheduler_SMP_Enqueue_ordered(
+  return _Scheduler_SMP_Enqueue_ordered(
     context,
     node,
+    needs_help,
     _Scheduler_priority_affinity_SMP_Insert_priority_fifo_order,
     _Scheduler_priority_SMP_Insert_ready_fifo,
     _Scheduler_SMP_Insert_scheduled_fifo,
@@ -374,14 +376,15 @@ static void _Scheduler_priority_affinity_SMP_Check_for_migrations(
 /*
  * This is the public scheduler specific Unblock operation.
  */
-void _Scheduler_priority_affinity_SMP_Unblock(
+Thread_Control *_Scheduler_priority_affinity_SMP_Unblock(
   const Scheduler_Control *scheduler,
   Thread_Control *thread
 )
 {
   Scheduler_Context *context = _Scheduler_Get_context( scheduler );
+  Thread_Control    *needs_help;
 
-  _Scheduler_SMP_Unblock(
+  needs_help = _Scheduler_SMP_Unblock(
     context,
     thread,
     _Scheduler_priority_affinity_SMP_Enqueue_fifo
@@ -391,23 +394,27 @@ void _Scheduler_priority_affinity_SMP_Unblock(
    * Perform any thread migrations that are needed due to these changes.
    */
   _Scheduler_priority_affinity_SMP_Check_for_migrations( context );
+
+  return needs_help;
 }
 
 /*
  *  This is unique to this scheduler because it passes scheduler specific
  *  get_lowest_scheduled helper to _Scheduler_SMP_Enqueue_ordered.
  */
-static void _Scheduler_priority_affinity_SMP_Enqueue_ordered(
+static Thread_Control *_Scheduler_priority_affinity_SMP_Enqueue_ordered(
   Scheduler_Context     *context,
   Scheduler_Node        *node,
+  Thread_Control        *needs_help,
   Chain_Node_order       order,
   Scheduler_SMP_Insert   insert_ready,
   Scheduler_SMP_Insert   insert_scheduled
 )
 {
-  _Scheduler_SMP_Enqueue_ordered(
+  return _Scheduler_SMP_Enqueue_ordered(
     context,
     node,
+    needs_help,
     order,
     insert_ready,
     insert_scheduled,
@@ -422,14 +429,16 @@ static void _Scheduler_priority_affinity_SMP_Enqueue_ordered(
  *  to _Scheduler_priority_affinity_SMP_Enqueue_ordered() which
  *  invokes a scheduler unique get_lowest_scheduled helper.
  */
-static void _Scheduler_priority_affinity_SMP_Enqueue_lifo(
+static Thread_Control *_Scheduler_priority_affinity_SMP_Enqueue_lifo(
   Scheduler_Context *context,
-  Scheduler_Node    *node
+  Scheduler_Node    *node,
+  Thread_Control    *needs_help
 )
 {
-  _Scheduler_priority_affinity_SMP_Enqueue_ordered(
+  return _Scheduler_priority_affinity_SMP_Enqueue_ordered(
     context,
     node,
+    needs_help,
     _Scheduler_priority_affinity_SMP_Insert_priority_lifo_order,
     _Scheduler_priority_SMP_Insert_ready_lifo,
     _Scheduler_SMP_Insert_scheduled_lifo
@@ -441,7 +450,8 @@ static void _Scheduler_priority_affinity_SMP_Enqueue_lifo(
  * invoke _Scheduler_SMP_Enqueue_scheduled_ordered() with
  * this scheduler's get_highest_ready() helper.
  */
-static void _Scheduler_priority_affinity_SMP_Enqueue_scheduled_ordered(
+static Thread_Control *
+_Scheduler_priority_affinity_SMP_Enqueue_scheduled_ordered(
   Scheduler_Context    *context,
   Scheduler_Node       *node,
   Chain_Node_order      order,
@@ -449,7 +459,7 @@ static void _Scheduler_priority_affinity_SMP_Enqueue_scheduled_ordered(
   Scheduler_SMP_Insert  insert_scheduled
 )
 {
-  _Scheduler_SMP_Enqueue_scheduled_ordered(
+  return _Scheduler_SMP_Enqueue_scheduled_ordered(
     context,
     node,
     order,
@@ -466,12 +476,12 @@ static void _Scheduler_priority_affinity_SMP_Enqueue_scheduled_ordered(
  *  to _Scheduler_priority_affinity_SMP_Enqueue_scheduled__ordered() which
  *  invokes a scheduler unique get_lowest_scheduled helper.
  */
-static void _Scheduler_priority_affinity_SMP_Enqueue_scheduled_lifo(
+static Thread_Control *_Scheduler_priority_affinity_SMP_Enqueue_scheduled_lifo(
   Scheduler_Context *context,
   Scheduler_Node    *node
 )
 {
-  _Scheduler_priority_affinity_SMP_Enqueue_scheduled_ordered(
+  return _Scheduler_priority_affinity_SMP_Enqueue_scheduled_ordered(
     context,
     node,
     _Scheduler_SMP_Insert_priority_lifo_order,
@@ -485,12 +495,12 @@ static void _Scheduler_priority_affinity_SMP_Enqueue_scheduled_lifo(
  *  to _Scheduler_priority_affinity_SMP_Enqueue_scheduled__ordered() which
  *  invokes a scheduler unique get_lowest_scheduled helper.
  */
-static void _Scheduler_priority_affinity_SMP_Enqueue_scheduled_fifo(
+static Thread_Control *_Scheduler_priority_affinity_SMP_Enqueue_scheduled_fifo(
   Scheduler_Context *context,
   Scheduler_Node    *node
 )
 {
-  _Scheduler_priority_affinity_SMP_Enqueue_scheduled_ordered(
+  return _Scheduler_priority_affinity_SMP_Enqueue_scheduled_ordered(
     context,
     node,
     _Scheduler_SMP_Insert_priority_fifo_order,
@@ -502,7 +512,7 @@ static void _Scheduler_priority_affinity_SMP_Enqueue_scheduled_fifo(
 /*
  * This is the public scheduler specific Change Priority operation.
  */
-void _Scheduler_priority_affinity_SMP_Change_priority(
+Thread_Control *_Scheduler_priority_affinity_SMP_Change_priority(
   const Scheduler_Control *scheduler,
   Thread_Control          *thread,
   Priority_Control         new_priority,
@@ -510,8 +520,9 @@ void _Scheduler_priority_affinity_SMP_Change_priority(
 )
 {
   Scheduler_Context *context = _Scheduler_Get_context( scheduler );
+  Thread_Control    *displaced;
 
-  _Scheduler_SMP_Change_priority(
+  displaced = _Scheduler_SMP_Change_priority(
     context,
     thread,
     new_priority,
@@ -528,6 +539,8 @@ void _Scheduler_priority_affinity_SMP_Change_priority(
    * Perform any thread migrations that are needed due to these changes.
    */
   _Scheduler_priority_affinity_SMP_Check_for_migrations( context );
+
+  return displaced;
 }
 
 /*
diff --git a/cpukit/score/src/schedulerprioritychangepriority.c b/cpukit/score/src/schedulerprioritychangepriority.c
index 4f00af6ad6..06c5f0f7c6 100644
--- a/cpukit/score/src/schedulerprioritychangepriority.c
+++ b/cpukit/score/src/schedulerprioritychangepriority.c
@@ -21,7 +21,7 @@
 
 #include <rtems/score/schedulerpriorityimpl.h>
 
-void _Scheduler_priority_Change_priority(
+Scheduler_Void_or_thread _Scheduler_priority_Change_priority(
   const Scheduler_Control *scheduler,
   Thread_Control          *the_thread,
   Priority_Control         new_priority,
@@ -58,4 +58,6 @@ void _Scheduler_priority_Change_priority(
       &context->Bit_map
     );
   }
+
+  SCHEDULER_RETURN_VOID_OR_NULL;
 }
diff --git a/cpukit/score/src/schedulerprioritysmp.c b/cpukit/score/src/schedulerprioritysmp.c
index 1f6d608538..b642c5d6f3 100644
--- a/cpukit/score/src/schedulerprioritysmp.c
+++ b/cpukit/score/src/schedulerprioritysmp.c
@@ -97,17 +97,19 @@ void _Scheduler_priority_SMP_Block(
   );
 }
 
-static void _Scheduler_priority_SMP_Enqueue_ordered(
-  Scheduler_Context *context,
-  Scheduler_Node *node,
-  Chain_Node_order order,
-  Scheduler_SMP_Insert insert_ready,
-  Scheduler_SMP_Insert insert_scheduled
+static Thread_Control *_Scheduler_priority_SMP_Enqueue_ordered(
+  Scheduler_Context    *context,
+  Scheduler_Node       *node,
+  Thread_Control       *needs_help,
+  Chain_Node_order      order,
+  Scheduler_SMP_Insert  insert_ready,
+  Scheduler_SMP_Insert  insert_scheduled
 )
 {
-  _Scheduler_SMP_Enqueue_ordered(
+  return _Scheduler_SMP_Enqueue_ordered(
     context,
     node,
+    needs_help,
     order,
     insert_ready,
     insert_scheduled,
@@ -117,35 +119,39 @@ static void _Scheduler_priority_SMP_Enqueue_ordered(
   );
 }
 
-static void _Scheduler_priority_SMP_Enqueue_lifo(
+static Thread_Control *_Scheduler_priority_SMP_Enqueue_lifo(
   Scheduler_Context *context,
-  Scheduler_Node *node
+  Scheduler_Node    *node,
+  Thread_Control    *needs_help
 )
 {
-  _Scheduler_priority_SMP_Enqueue_ordered(
+  return _Scheduler_priority_SMP_Enqueue_ordered(
     context,
     node,
+    needs_help,
     _Scheduler_SMP_Insert_priority_lifo_order,
     _Scheduler_priority_SMP_Insert_ready_lifo,
     _Scheduler_SMP_Insert_scheduled_lifo
   );
 }
 
-static void _Scheduler_priority_SMP_Enqueue_fifo(
+static Thread_Control *_Scheduler_priority_SMP_Enqueue_fifo(
   Scheduler_Context *context,
-  Scheduler_Node *node
+  Scheduler_Node    *node,
+  Thread_Control    *needs_help
 )
 {
-  _Scheduler_priority_SMP_Enqueue_ordered(
+  return _Scheduler_priority_SMP_Enqueue_ordered(
     context,
     node,
+    needs_help,
     _Scheduler_SMP_Insert_priority_fifo_order,
     _Scheduler_priority_SMP_Insert_ready_fifo,
     _Scheduler_SMP_Insert_scheduled_fifo
   );
 }
 
-static void _Scheduler_priority_SMP_Enqueue_scheduled_ordered(
+static Thread_Control *_Scheduler_priority_SMP_Enqueue_scheduled_ordered(
   Scheduler_Context *context,
   Scheduler_Node *node,
   Chain_Node_order order,
@@ -153,7 +159,7 @@ static void _Scheduler_priority_SMP_Enqueue_scheduled_ordered(
   Scheduler_SMP_Insert insert_scheduled
 )
 {
-  _Scheduler_SMP_Enqueue_scheduled_ordered(
+  return _Scheduler_SMP_Enqueue_scheduled_ordered(
     context,
     node,
     order,
@@ -165,12 +171,12 @@ static void _Scheduler_priority_SMP_Enqueue_scheduled_ordered(
   );
 }
 
-static void _Scheduler_priority_SMP_Enqueue_scheduled_lifo(
+static Thread_Control *_Scheduler_priority_SMP_Enqueue_scheduled_lifo(
   Scheduler_Context *context,
   Scheduler_Node *node
 )
 {
-  _Scheduler_priority_SMP_Enqueue_scheduled_ordered(
+  return _Scheduler_priority_SMP_Enqueue_scheduled_ordered(
     context,
     node,
     _Scheduler_SMP_Insert_priority_lifo_order,
@@ -179,12 +185,12 @@ static void _Scheduler_priority_SMP_Enqueue_scheduled_lifo(
   );
 }
 
-static void _Scheduler_priority_SMP_Enqueue_scheduled_fifo(
+static Thread_Control *_Scheduler_priority_SMP_Enqueue_scheduled_fifo(
   Scheduler_Context *context,
   Scheduler_Node *node
 )
 {
-  _Scheduler_priority_SMP_Enqueue_scheduled_ordered(
+  return _Scheduler_priority_SMP_Enqueue_scheduled_ordered(
     context,
     node,
     _Scheduler_SMP_Insert_priority_fifo_order,
@@ -193,21 +199,21 @@ static void _Scheduler_priority_SMP_Enqueue_scheduled_fifo(
   );
 }
 
-void _Scheduler_priority_SMP_Unblock(
+Thread_Control *_Scheduler_priority_SMP_Unblock(
   const Scheduler_Control *scheduler,
   Thread_Control *thread
 )
 {
   Scheduler_Context *context = _Scheduler_Get_context( scheduler );
 
-  _Scheduler_SMP_Unblock(
+  return _Scheduler_SMP_Unblock(
     context,
     thread,
     _Scheduler_priority_SMP_Enqueue_fifo
   );
 }
 
-void _Scheduler_priority_SMP_Change_priority(
+Thread_Control *_Scheduler_priority_SMP_Change_priority(
   const Scheduler_Control *scheduler,
   Thread_Control          *thread,
   Priority_Control         new_priority,
@@ -216,7 +222,7 @@ void _Scheduler_priority_SMP_Change_priority(
 {
   Scheduler_Context *context = _Scheduler_Get_context( scheduler );
 
-  _Scheduler_SMP_Change_priority(
+  return _Scheduler_SMP_Change_priority(
     context,
     thread,
     new_priority,
@@ -230,7 +236,7 @@ void _Scheduler_priority_SMP_Change_priority(
   );
 }
 
-void _Scheduler_priority_SMP_Yield(
+Thread_Control *_Scheduler_priority_SMP_Yield(
   const Scheduler_Control *scheduler,
   Thread_Control *thread
 )
diff --git a/cpukit/score/src/schedulerpriorityunblock.c b/cpukit/score/src/schedulerpriorityunblock.c
index c1f12f44c6..06d29f3b91 100644
--- a/cpukit/score/src/schedulerpriorityunblock.c
+++ b/cpukit/score/src/schedulerpriorityunblock.c
@@ -22,7 +22,7 @@
 
 #include <rtems/score/schedulerpriorityimpl.h>
 
-void _Scheduler_priority_Unblock (
+Scheduler_Void_or_thread _Scheduler_priority_Unblock (
   const Scheduler_Control *scheduler,
   Thread_Control          *the_thread
 )
@@ -57,4 +57,6 @@ void _Scheduler_priority_Unblock (
         the_thread->current_priority == 0 )
       _Thread_Dispatch_necessary = true;
   }
+
+  SCHEDULER_RETURN_VOID_OR_NULL;
 }
diff --git a/cpukit/score/src/schedulerpriorityyield.c b/cpukit/score/src/schedulerpriorityyield.c
index de4b842513..2ee2d03057 100644
--- a/cpukit/score/src/schedulerpriorityyield.c
+++ b/cpukit/score/src/schedulerpriorityyield.c
@@ -21,7 +21,7 @@
 #include <rtems/score/schedulerpriorityimpl.h>
 #include <rtems/score/threadimpl.h>
 
-void _Scheduler_priority_Yield(
+Scheduler_Void_or_thread _Scheduler_priority_Yield(
   const Scheduler_Control *scheduler,
   Thread_Control          *the_thread
 )
@@ -43,4 +43,6 @@ void _Scheduler_priority_Yield(
   } else if ( !_Thread_Is_heir( the_thread ) ) {
     _Thread_Dispatch_necessary = true;
   }
+
+  SCHEDULER_RETURN_VOID_OR_NULL;
 }
diff --git a/cpukit/score/src/schedulersimplechangepriority.c b/cpukit/score/src/schedulersimplechangepriority.c
index 010f1dfc79..b8638ad28c 100644
--- a/cpukit/score/src/schedulersimplechangepriority.c
+++ b/cpukit/score/src/schedulersimplechangepriority.c
@@ -21,7 +21,7 @@
 
 #include <rtems/score/schedulersimpleimpl.h>
 
-void _Scheduler_simple_Change_priority(
+Scheduler_Void_or_thread _Scheduler_simple_Change_priority(
   const Scheduler_Control *scheduler,
   Thread_Control          *the_thread,
   Priority_Control         new_priority,
@@ -38,4 +38,6 @@ void _Scheduler_simple_Change_priority(
   } else {
     _Scheduler_simple_Insert_priority_fifo( &context->Ready, the_thread );
   }
+
+  SCHEDULER_RETURN_VOID_OR_NULL;
 }
diff --git a/cpukit/score/src/schedulersimplesmp.c b/cpukit/score/src/schedulersimplesmp.c
index 7361678e53..ee540bebd0 100644
--- a/cpukit/score/src/schedulersimplesmp.c
+++ b/cpukit/score/src/schedulersimplesmp.c
@@ -179,17 +179,19 @@ void _Scheduler_simple_SMP_Block(
   );
 }
 
-static void _Scheduler_simple_SMP_Enqueue_ordered(
-  Scheduler_Context *context,
-  Scheduler_Node *node,
-  Chain_Node_order order,
-  Scheduler_SMP_Insert insert_ready,
-  Scheduler_SMP_Insert insert_scheduled
+static Thread_Control *_Scheduler_simple_SMP_Enqueue_ordered(
+  Scheduler_Context    *context,
+  Scheduler_Node       *node,
+  Thread_Control       *needs_help,
+  Chain_Node_order      order,
+  Scheduler_SMP_Insert  insert_ready,
+  Scheduler_SMP_Insert  insert_scheduled
 )
 {
-  _Scheduler_SMP_Enqueue_ordered(
+  return _Scheduler_SMP_Enqueue_ordered(
     context,
     node,
+    needs_help,
     order,
     insert_ready,
     insert_scheduled,
@@ -199,35 +201,39 @@ static void _Scheduler_simple_SMP_Enqueue_ordered(
   );
 }
 
-static void _Scheduler_simple_SMP_Enqueue_lifo(
+static Thread_Control *_Scheduler_simple_SMP_Enqueue_lifo(
   Scheduler_Context *context,
-  Scheduler_Node *node
+  Scheduler_Node    *node,
+  Thread_Control    *needs_help
 )
 {
-  _Scheduler_simple_SMP_Enqueue_ordered(
+  return _Scheduler_simple_SMP_Enqueue_ordered(
     context,
     node,
+    needs_help,
     _Scheduler_SMP_Insert_priority_lifo_order,
     _Scheduler_simple_SMP_Insert_ready_lifo,
     _Scheduler_SMP_Insert_scheduled_lifo
   );
 }
 
-static void _Scheduler_simple_SMP_Enqueue_fifo(
+static Thread_Control *_Scheduler_simple_SMP_Enqueue_fifo(
   Scheduler_Context *context,
-  Scheduler_Node *node
+  Scheduler_Node    *node,
+  Thread_Control    *needs_help
 )
 {
-  _Scheduler_simple_SMP_Enqueue_ordered(
+  return _Scheduler_simple_SMP_Enqueue_ordered(
     context,
     node,
+    needs_help,
     _Scheduler_SMP_Insert_priority_fifo_order,
     _Scheduler_simple_SMP_Insert_ready_fifo,
     _Scheduler_SMP_Insert_scheduled_fifo
   );
 }
 
-static void _Scheduler_simple_SMP_Enqueue_scheduled_ordered(
+static Thread_Control *_Scheduler_simple_SMP_Enqueue_scheduled_ordered(
   Scheduler_Context *context,
   Scheduler_Node *node,
   Chain_Node_order order,
@@ -235,7 +241,7 @@ static void _Scheduler_simple_SMP_Enqueue_scheduled_ordered(
   Scheduler_SMP_Insert insert_scheduled
 )
 {
-  _Scheduler_SMP_Enqueue_scheduled_ordered(
+  return _Scheduler_SMP_Enqueue_scheduled_ordered(
     context,
     node,
     order,
@@ -247,12 +253,12 @@ static void _Scheduler_simple_SMP_Enqueue_scheduled_ordered(
   );
 }
 
-static void _Scheduler_simple_SMP_Enqueue_scheduled_lifo(
+static Thread_Control *_Scheduler_simple_SMP_Enqueue_scheduled_lifo(
   Scheduler_Context *context,
   Scheduler_Node *node
 )
 {
-  _Scheduler_simple_SMP_Enqueue_scheduled_ordered(
+  return _Scheduler_simple_SMP_Enqueue_scheduled_ordered(
     context,
     node,
     _Scheduler_SMP_Insert_priority_lifo_order,
@@ -261,12 +267,12 @@ static void _Scheduler_simple_SMP_Enqueue_scheduled_lifo(
   );
 }
 
-static void _Scheduler_simple_SMP_Enqueue_scheduled_fifo(
+static Thread_Control *_Scheduler_simple_SMP_Enqueue_scheduled_fifo(
   Scheduler_Context *context,
   Scheduler_Node *node
 )
 {
-  _Scheduler_simple_SMP_Enqueue_scheduled_ordered(
+  return _Scheduler_simple_SMP_Enqueue_scheduled_ordered(
     context,
     node,
     _Scheduler_SMP_Insert_priority_fifo_order,
@@ -275,21 +281,21 @@ static void _Scheduler_simple_SMP_Enqueue_scheduled_fifo(
   );
 }
 
-void _Scheduler_simple_SMP_Unblock(
+Thread_Control *_Scheduler_simple_SMP_Unblock(
   const Scheduler_Control *scheduler,
   Thread_Control *thread
 )
 {
   Scheduler_Context *context = _Scheduler_Get_context( scheduler );
 
-  _Scheduler_SMP_Unblock(
+  return _Scheduler_SMP_Unblock(
     context,
     thread,
     _Scheduler_simple_SMP_Enqueue_fifo
   );
 }
 
-void _Scheduler_simple_SMP_Change_priority(
+Thread_Control *_Scheduler_simple_SMP_Change_priority(
   const Scheduler_Control *scheduler,
   Thread_Control          *thread,
   Priority_Control         new_priority,
@@ -298,7 +304,7 @@ void _Scheduler_simple_SMP_Change_priority(
 {
   Scheduler_Context *context = _Scheduler_Get_context( scheduler );
 
-  _Scheduler_SMP_Change_priority(
+  return _Scheduler_SMP_Change_priority(
     context,
     thread,
     new_priority,
@@ -312,7 +318,7 @@ void _Scheduler_simple_SMP_Change_priority(
   );
 }
 
-void _Scheduler_simple_SMP_Yield(
+Thread_Control *_Scheduler_simple_SMP_Yield(
   const Scheduler_Control *scheduler,
   Thread_Control *thread
 )
diff --git a/cpukit/score/src/schedulersimpleunblock.c b/cpukit/score/src/schedulersimpleunblock.c
index 4e49bd6697..6f9b2f719f 100644
--- a/cpukit/score/src/schedulersimpleunblock.c
+++ b/cpukit/score/src/schedulersimpleunblock.c
@@ -21,7 +21,7 @@
 #include <rtems/score/schedulersimpleimpl.h>
 #include <rtems/score/thread.h>
 
-void _Scheduler_simple_Unblock(
+Scheduler_Void_or_thread _Scheduler_simple_Unblock(
   const Scheduler_Control *scheduler,
   Thread_Control          *the_thread
 )
@@ -49,4 +49,6 @@ void _Scheduler_simple_Unblock(
         the_thread->current_priority == 0 )
       _Thread_Dispatch_necessary = true;
   }
+
+  SCHEDULER_RETURN_VOID_OR_NULL;
 }
diff --git a/cpukit/score/src/schedulersimpleyield.c b/cpukit/score/src/schedulersimpleyield.c
index b807530600..66e4450477 100644
--- a/cpukit/score/src/schedulersimpleyield.c
+++ b/cpukit/score/src/schedulersimpleyield.c
@@ -20,7 +20,7 @@
 
 #include <rtems/score/schedulersimpleimpl.h>
 
-void _Scheduler_simple_Yield(
+Scheduler_Void_or_thread _Scheduler_simple_Yield(
   const Scheduler_Control *scheduler,
   Thread_Control          *the_thread
 )
@@ -31,4 +31,6 @@ void _Scheduler_simple_Yield(
   _Chain_Extract_unprotected( &the_thread->Object.Node );
   _Scheduler_simple_Insert_priority_fifo( &context->Ready, the_thread );
   _Scheduler_simple_Schedule_body( scheduler, the_thread, false );
+
+  SCHEDULER_RETURN_VOID_OR_NULL;
 }