score: Fix scheduler helping implementation

Do not extract the idle threads from the ready set so that there is
always a thread available for comparison.

6 files changed, 39 insertions, 119 deletions

diff --git a/cpukit/score/include/rtems/score/schedulerprioritysmpimpl.h b/cpukit/score/include/rtems/score/schedulerprioritysmpimpl.h
index bb200b4641..9ae01038b6 100644
--- a/cpukit/score/include/rtems/score/schedulerprioritysmpimpl.h
+++ b/cpukit/score/include/rtems/score/schedulerprioritysmpimpl.h
@@ -148,28 +148,6 @@ static inline void _Scheduler_priority_SMP_Extract_from_ready(
   );
 }
 
-static inline Thread_Control *_Scheduler_priority_SMP_Get_idle_thread(
-  Scheduler_Context *context
-)
-{
-  return _Scheduler_SMP_Get_idle_thread(
-    context,
-    _Scheduler_priority_SMP_Extract_from_ready
-  );
-}
-
-static void _Scheduler_priority_SMP_Release_idle_thread(
-  Scheduler_Context *context,
-  Thread_Control    *idle
-)
-{
-  _Scheduler_SMP_Release_idle_thread(
-    context,
-    idle,
-    _Scheduler_priority_SMP_Insert_ready_fifo
-  );
-}
-
 static inline void _Scheduler_priority_SMP_Do_update(
   Scheduler_Context *context,
   Scheduler_Node *node_to_update,
diff --git a/cpukit/score/include/rtems/score/schedulersmp.h b/cpukit/score/include/rtems/score/schedulersmp.h
index a58417a268..9e11488584 100644
--- a/cpukit/score/include/rtems/score/schedulersmp.h
+++ b/cpukit/score/include/rtems/score/schedulersmp.h
@@ -54,6 +54,10 @@ typedef struct {
 
   /**
    * @brief Chain of the available idle threads.
+   *
+   * Idle threads are used for the scheduler helping protocol.  It is crucial
+   * that the idle threads preserve their relative order.  This is the case for
+   * this priority based scheduler.
    */
   Chain_Control Idle_threads;
 } Scheduler_SMP_Context;
diff --git a/cpukit/score/include/rtems/score/schedulersmpimpl.h b/cpukit/score/include/rtems/score/schedulersmpimpl.h
index a4890df4d0..156307db24 100644
--- a/cpukit/score/include/rtems/score/schedulersmpimpl.h
+++ b/cpukit/score/include/rtems/score/schedulersmpimpl.h
@@ -425,16 +425,12 @@ static inline bool _Scheduler_SMP_Is_processor_owned_by_us(
 }
 
 static inline Thread_Control *_Scheduler_SMP_Get_idle_thread(
-  Scheduler_Context     *context,
-  Scheduler_SMP_Extract  extract_from_ready
+  Scheduler_Context *context
 )
 {
   Scheduler_SMP_Context *self = _Scheduler_SMP_Get_self( context );
   Thread_Control *idle = (Thread_Control *)
     _Chain_Get_first_unprotected( &self->Idle_threads );
-  Scheduler_Node *own_node = _Scheduler_Thread_get_own_node( idle );
-
-  ( *extract_from_ready )( &self->Base, own_node );
 
   _Assert( &idle->Object.Node != _Chain_Tail( &self->Idle_threads ) );
 
@@ -442,16 +438,13 @@ static inline Thread_Control *_Scheduler_SMP_Get_idle_thread(
 }
 
 static inline void _Scheduler_SMP_Release_idle_thread(
-  Scheduler_Context    *context,
-  Thread_Control       *idle,
-  Scheduler_SMP_Insert  insert_ready
+  Scheduler_Context *context,
+  Thread_Control    *idle
 )
 {
   Scheduler_SMP_Context *self = _Scheduler_SMP_Get_self( context );
-  Scheduler_Node *own_node = _Scheduler_Thread_get_own_node( idle );
 
   _Chain_Prepend_unprotected( &self->Idle_threads, &idle->Object.Node );
-  ( *insert_ready )( context, own_node );
 }
 
 static inline void _Scheduler_SMP_Allocate_processor_lazy(
@@ -536,8 +529,7 @@ static inline Thread_Control *_Scheduler_SMP_Enqueue_to_scheduled(
   Scheduler_Node                   *lowest_scheduled,
   Scheduler_SMP_Insert              insert_scheduled,
   Scheduler_SMP_Move                move_from_scheduled_to_ready,
-  Scheduler_SMP_Allocate_processor  allocate_processor,
-  Scheduler_Release_idle_thread     release_idle_thread
+  Scheduler_SMP_Allocate_processor  allocate_processor
 )
 {
   Thread_Control *user = _Scheduler_Node_get_user( node );
@@ -570,7 +562,7 @@ static inline Thread_Control *_Scheduler_SMP_Enqueue_to_scheduled(
   idle = _Scheduler_Release_idle_thread(
     context,
     lowest_scheduled,
-    release_idle_thread
+    _Scheduler_SMP_Release_idle_thread
   );
   if ( idle == NULL ) {
     needs_help = lowest_scheduled_user;
@@ -603,7 +595,6 @@ static inline Thread_Control *_Scheduler_SMP_Enqueue_to_scheduled(
  *   if this pointer is passed as the second argument to the order function.
  * @param[in] allocate_processor Function to allocate a processor to a node
  *   based on the rules of the scheduler.
- * @param[in] release_idle_thread Function to release an idle thread.
  */
 static inline Thread_Control *_Scheduler_SMP_Enqueue_ordered(
   Scheduler_Context                  *context,
@@ -614,8 +605,7 @@ static inline Thread_Control *_Scheduler_SMP_Enqueue_ordered(
   Scheduler_SMP_Insert                insert_scheduled,
   Scheduler_SMP_Move                  move_from_scheduled_to_ready,
   Scheduler_SMP_Get_lowest_scheduled  get_lowest_scheduled,
-  Scheduler_SMP_Allocate_processor    allocate_processor,
-  Scheduler_Release_idle_thread       release_idle_thread
+  Scheduler_SMP_Allocate_processor    allocate_processor
 )
 {
   Scheduler_Node *lowest_scheduled =
@@ -628,8 +618,7 @@ static inline Thread_Control *_Scheduler_SMP_Enqueue_ordered(
       lowest_scheduled,
       insert_scheduled,
       move_from_scheduled_to_ready,
-      allocate_processor,
-      release_idle_thread
+      allocate_processor
     );
   } else {
     ( *insert_ready )( context, node );
@@ -656,8 +645,6 @@ static inline Thread_Control *_Scheduler_SMP_Enqueue_ordered(
  *   of ready nodes to the set of scheduled nodes.
  * @param[in] allocate_processor Function to allocate a processor to a node
  *   based on the rules of the scheduler.
- * @param[in] get_idle_thread Function to get an idle thread.
- * @param[in] release_idle_thread Function to release an idle thread.
  */
 static inline Thread_Control *_Scheduler_SMP_Enqueue_scheduled_ordered(
   Scheduler_Context                *context,
@@ -668,9 +655,7 @@ static inline Thread_Control *_Scheduler_SMP_Enqueue_scheduled_ordered(
   Scheduler_SMP_Insert              insert_ready,
   Scheduler_SMP_Insert              insert_scheduled,
   Scheduler_SMP_Move                move_from_ready_to_scheduled,
-  Scheduler_SMP_Allocate_processor  allocate_processor,
-  Scheduler_Get_idle_thread         get_idle_thread,
-  Scheduler_Release_idle_thread     release_idle_thread
+  Scheduler_SMP_Allocate_processor  allocate_processor
 )
 {
   Thread_Control *needs_help;
@@ -692,7 +677,7 @@ static inline Thread_Control *_Scheduler_SMP_Enqueue_scheduled_ordered(
       _Scheduler_Try_to_schedule_node(
         context,
         highest_ready,
-        get_idle_thread
+        _Scheduler_SMP_Get_idle_thread
       )
     ) {
       Thread_Control *user = _Scheduler_Node_get_user( node );
@@ -717,7 +702,7 @@ static inline Thread_Control *_Scheduler_SMP_Enqueue_scheduled_ordered(
       idle = _Scheduler_Release_idle_thread(
         context,
         node,
-        release_idle_thread
+        _Scheduler_SMP_Release_idle_thread
       );
       if ( idle == NULL ) {
         needs_help = user;
@@ -752,8 +737,7 @@ static inline void _Scheduler_SMP_Schedule_highest_ready(
   Scheduler_SMP_Extract             extract_from_ready,
   Scheduler_SMP_Get_highest_ready   get_highest_ready,
   Scheduler_SMP_Move                move_from_ready_to_scheduled,
-  Scheduler_SMP_Allocate_processor  allocate_processor,
-  Scheduler_Get_idle_thread         get_idle_thread
+  Scheduler_SMP_Allocate_processor  allocate_processor
 )
 {
   while ( true ) {
@@ -763,7 +747,7 @@ static inline void _Scheduler_SMP_Schedule_highest_ready(
       _Scheduler_Try_to_schedule_node(
         context,
         highest_ready,
-        get_idle_thread
+        _Scheduler_SMP_Get_idle_thread
       )
     ) {
       _Scheduler_SMP_Allocate_processor(
@@ -797,7 +781,6 @@ static inline void _Scheduler_SMP_Schedule_highest_ready(
  * @param[in] get_highest_ready Function to get the highest ready node.
  * @param[in] move_from_ready_to_scheduled Function to move a node from the set
  *   of ready nodes to the set of scheduled nodes.
- * @param[in] get_idle_thread Function to get an idle thread.
  */
 static inline void _Scheduler_SMP_Block(
   Scheduler_Context                *context,
@@ -805,8 +788,7 @@ static inline void _Scheduler_SMP_Block(
   Scheduler_SMP_Extract             extract_from_ready,
   Scheduler_SMP_Get_highest_ready   get_highest_ready,
   Scheduler_SMP_Move                move_from_ready_to_scheduled,
-  Scheduler_SMP_Allocate_processor  allocate_processor,
-  Scheduler_Get_idle_thread         get_idle_thread
+  Scheduler_SMP_Allocate_processor  allocate_processor
 )
 {
   Scheduler_SMP_Node *node = _Scheduler_SMP_Thread_get_node( thread );
@@ -815,7 +797,7 @@ static inline void _Scheduler_SMP_Block(
     context,
     &node->Base,
     is_scheduled,
-    get_idle_thread
+    _Scheduler_SMP_Get_idle_thread
   );
 
   if ( block ) {
@@ -830,8 +812,7 @@ static inline void _Scheduler_SMP_Block(
         extract_from_ready,
         get_highest_ready,
         move_from_ready_to_scheduled,
-        allocate_processor,
-        get_idle_thread
+        allocate_processor
       );
     } else {
       ( *extract_from_ready )( context, &node->Base );
@@ -842,8 +823,7 @@ static inline void _Scheduler_SMP_Block(
 static inline Thread_Control *_Scheduler_SMP_Unblock(
   Scheduler_Context             *context,
   Thread_Control                *thread,
-  Scheduler_SMP_Enqueue          enqueue_fifo,
-  Scheduler_Release_idle_thread  release_idle_thread
+  Scheduler_SMP_Enqueue          enqueue_fifo
 )
 {
   Scheduler_SMP_Node *node = _Scheduler_SMP_Thread_get_node( thread );
@@ -853,7 +833,7 @@ static inline Thread_Control *_Scheduler_SMP_Unblock(
     thread,
     &node->Base,
     is_scheduled,
-    release_idle_thread
+    _Scheduler_SMP_Release_idle_thread
   );
   Thread_Control *needs_help;
 
@@ -917,8 +897,7 @@ static inline Thread_Control *_Scheduler_SMP_Ask_for_help(
   Scheduler_Context                  *context,
   Thread_Control                     *offers_help,
   Thread_Control                     *needs_help,
-  Scheduler_SMP_Enqueue               enqueue_fifo,
-  Scheduler_Release_idle_thread       release_idle_thread
+  Scheduler_SMP_Enqueue               enqueue_fifo
 )
 {
   Scheduler_SMP_Node *node = _Scheduler_SMP_Thread_get_own_node( offers_help );
@@ -940,7 +919,7 @@ static inline Thread_Control *_Scheduler_SMP_Ask_for_help(
         offers_help,
         needs_help,
         previous_accepts_help,
-        release_idle_thread
+        _Scheduler_SMP_Release_idle_thread
       );
       break;
     case SCHEDULER_SMP_NODE_BLOCKED:
diff --git a/cpukit/score/src/schedulerpriorityaffinitysmp.c b/cpukit/score/src/schedulerpriorityaffinitysmp.c
index 39a0a481ea..41e44a0834 100644
--- a/cpukit/score/src/schedulerpriorityaffinitysmp.c
+++ b/cpukit/score/src/schedulerpriorityaffinitysmp.c
@@ -231,8 +231,7 @@ void _Scheduler_priority_affinity_SMP_Block(
     _Scheduler_priority_SMP_Extract_from_ready,
     _Scheduler_priority_affinity_SMP_Get_highest_ready,
     _Scheduler_priority_SMP_Move_from_ready_to_scheduled,
-    _Scheduler_SMP_Allocate_processor_exact,
-    _Scheduler_priority_SMP_Get_idle_thread
+    _Scheduler_SMP_Allocate_processor_exact
   );
 
   /*
@@ -314,8 +313,7 @@ static Thread_Control *_Scheduler_priority_affinity_SMP_Enqueue_fifo(
     _Scheduler_SMP_Insert_scheduled_fifo,
     _Scheduler_priority_SMP_Move_from_scheduled_to_ready,
     _Scheduler_priority_affinity_SMP_Get_lowest_scheduled,
-    _Scheduler_SMP_Allocate_processor_exact,
-    _Scheduler_priority_SMP_Release_idle_thread
+    _Scheduler_SMP_Allocate_processor_exact
   );
 }
 
@@ -399,8 +397,7 @@ Thread_Control *_Scheduler_priority_affinity_SMP_Unblock(
   needs_help = _Scheduler_SMP_Unblock(
     context,
     thread,
-    _Scheduler_priority_affinity_SMP_Enqueue_fifo,
-    _Scheduler_priority_SMP_Release_idle_thread
+    _Scheduler_priority_affinity_SMP_Enqueue_fifo
   );
 
   /*
@@ -433,8 +430,7 @@ static Thread_Control *_Scheduler_priority_affinity_SMP_Enqueue_ordered(
     insert_scheduled,
     _Scheduler_priority_SMP_Move_from_scheduled_to_ready,
     _Scheduler_priority_affinity_SMP_Get_lowest_scheduled,
-    _Scheduler_SMP_Allocate_processor_exact,
-    _Scheduler_priority_SMP_Release_idle_thread
+    _Scheduler_SMP_Allocate_processor_exact
   );
 }
 
@@ -482,9 +478,7 @@ _Scheduler_priority_affinity_SMP_Enqueue_scheduled_ordered(
     insert_ready,
     insert_scheduled,
     _Scheduler_priority_SMP_Move_from_ready_to_scheduled,
-    _Scheduler_SMP_Allocate_processor_exact,
-    _Scheduler_priority_SMP_Get_idle_thread,
-    _Scheduler_priority_SMP_Release_idle_thread
+    _Scheduler_SMP_Allocate_processor_exact
   );
 }
 
@@ -572,8 +566,7 @@ Thread_Control *_Scheduler_priority_affinity_SMP_Ask_for_help(
     context,
     offers_help,
     needs_help,
-    _Scheduler_priority_affinity_SMP_Enqueue_fifo,
-    _Scheduler_priority_SMP_Release_idle_thread
+    _Scheduler_priority_affinity_SMP_Enqueue_fifo
   );
 
   _Scheduler_priority_affinity_SMP_Check_for_migrations( context );
diff --git a/cpukit/score/src/schedulerprioritysmp.c b/cpukit/score/src/schedulerprioritysmp.c
index 93d1c76d30..c08799f270 100644
--- a/cpukit/score/src/schedulerprioritysmp.c
+++ b/cpukit/score/src/schedulerprioritysmp.c
@@ -93,8 +93,7 @@ void _Scheduler_priority_SMP_Block(
     _Scheduler_priority_SMP_Extract_from_ready,
     _Scheduler_priority_SMP_Get_highest_ready,
     _Scheduler_priority_SMP_Move_from_ready_to_scheduled,
-    _Scheduler_SMP_Allocate_processor_lazy,
-    _Scheduler_priority_SMP_Get_idle_thread
+    _Scheduler_SMP_Allocate_processor_lazy
   );
 }
 
@@ -116,8 +115,7 @@ static Thread_Control *_Scheduler_priority_SMP_Enqueue_ordered(
     insert_scheduled,
     _Scheduler_priority_SMP_Move_from_scheduled_to_ready,
     _Scheduler_SMP_Get_lowest_scheduled,
-    _Scheduler_SMP_Allocate_processor_lazy,
-    _Scheduler_priority_SMP_Release_idle_thread
+    _Scheduler_SMP_Allocate_processor_lazy
   );
 }
 
@@ -170,9 +168,7 @@ static Thread_Control *_Scheduler_priority_SMP_Enqueue_scheduled_ordered(
     insert_ready,
     insert_scheduled,
     _Scheduler_priority_SMP_Move_from_ready_to_scheduled,
-    _Scheduler_SMP_Allocate_processor_lazy,
-    _Scheduler_priority_SMP_Get_idle_thread,
-    _Scheduler_priority_SMP_Release_idle_thread
+    _Scheduler_SMP_Allocate_processor_lazy
   );
 }
 
@@ -214,8 +210,7 @@ Thread_Control *_Scheduler_priority_SMP_Unblock(
   return _Scheduler_SMP_Unblock(
     context,
     thread,
-    _Scheduler_priority_SMP_Enqueue_fifo,
-    _Scheduler_priority_SMP_Release_idle_thread
+    _Scheduler_priority_SMP_Enqueue_fifo
   );
 }
 
@@ -254,8 +249,7 @@ Thread_Control *_Scheduler_priority_SMP_Ask_for_help(
     context,
     offers_help,
     needs_help,
-    _Scheduler_priority_SMP_Enqueue_fifo,
-    _Scheduler_priority_SMP_Release_idle_thread
+    _Scheduler_priority_SMP_Enqueue_fifo
   );
 }
 
diff --git a/cpukit/score/src/schedulersimplesmp.c b/cpukit/score/src/schedulersimplesmp.c
index 733f3dbe9f..0f05a7da81 100644
--- a/cpukit/score/src/schedulersimplesmp.c
+++ b/cpukit/score/src/schedulersimplesmp.c
@@ -165,28 +165,6 @@ static void _Scheduler_simple_SMP_Extract_from_ready(
   _Chain_Extract_unprotected( &node_to_extract->Node );
 }
 
-static Thread_Control *_Scheduler_simple_SMP_Get_idle_thread(
-  Scheduler_Context *context
-)
-{
-  return _Scheduler_SMP_Get_idle_thread(
-    context,
-    _Scheduler_simple_SMP_Extract_from_ready
-  );
-}
-
-static void _Scheduler_simple_SMP_Release_idle_thread(
-  Scheduler_Context *context,
-  Thread_Control    *idle
-)
-{
-  _Scheduler_SMP_Release_idle_thread(
-    context,
-    idle,
-    _Scheduler_simple_SMP_Insert_ready_fifo
-  );
-}
-
 void _Scheduler_simple_SMP_Block(
   const Scheduler_Control *scheduler,
   Thread_Control *thread
@@ -200,8 +178,7 @@ void _Scheduler_simple_SMP_Block(
     _Scheduler_simple_SMP_Extract_from_ready,
     _Scheduler_simple_SMP_Get_highest_ready,
     _Scheduler_simple_SMP_Move_from_ready_to_scheduled,
-    _Scheduler_SMP_Allocate_processor_lazy,
-    _Scheduler_simple_SMP_Get_idle_thread
+    _Scheduler_SMP_Allocate_processor_lazy
   );
 }
 
@@ -223,8 +200,7 @@ static Thread_Control *_Scheduler_simple_SMP_Enqueue_ordered(
     insert_scheduled,
     _Scheduler_simple_SMP_Move_from_scheduled_to_ready,
     _Scheduler_SMP_Get_lowest_scheduled,
-    _Scheduler_SMP_Allocate_processor_lazy,
-    _Scheduler_simple_SMP_Release_idle_thread
+    _Scheduler_SMP_Allocate_processor_lazy
   );
 }
 
@@ -277,9 +253,7 @@ static Thread_Control *_Scheduler_simple_SMP_Enqueue_scheduled_ordered(
     insert_ready,
     insert_scheduled,
     _Scheduler_simple_SMP_Move_from_ready_to_scheduled,
-    _Scheduler_SMP_Allocate_processor_lazy,
-    _Scheduler_simple_SMP_Get_idle_thread,
-    _Scheduler_simple_SMP_Release_idle_thread
+    _Scheduler_SMP_Allocate_processor_lazy
   );
 }
 
@@ -321,8 +295,7 @@ Thread_Control *_Scheduler_simple_SMP_Unblock(
   return _Scheduler_SMP_Unblock(
     context,
     thread,
-    _Scheduler_simple_SMP_Enqueue_fifo,
-    _Scheduler_simple_SMP_Release_idle_thread
+    _Scheduler_simple_SMP_Enqueue_fifo
   );
 }
 
@@ -361,8 +334,7 @@ Thread_Control *_Scheduler_simple_SMP_Ask_for_help(
     context,
     offers_help,
     needs_help,
-    _Scheduler_simple_SMP_Enqueue_fifo,
-    _Scheduler_simple_SMP_Release_idle_thread
+    _Scheduler_simple_SMP_Enqueue_fifo
   );
 }