[PATCH 5/6] score: Add _Scheduler_Help()

[Sebastian Huber]

Manage the help state of threads with respect to scheduling decisions.
---
 cpukit/score/include/rtems/score/mrspimpl.h      |   27 +++++++++------
 cpukit/score/include/rtems/score/scheduler.h     |   40 ++++++++++++++++++++++
 cpukit/score/include/rtems/score/schedulerimpl.h |   30 ++++++++++++++++
 cpukit/score/include/rtems/score/threadimpl.h    |   10 +++++
 4 files changed, 96 insertions(+), 11 deletions(-)

diff --git a/cpukit/score/include/rtems/score/mrspimpl.h b/cpukit/score/include/rtems/score/mrspimpl.h
index 2369d9d..1f33d25 100644
--- a/cpukit/score/include/rtems/score/mrspimpl.h
+++ b/cpukit/score/include/rtems/score/mrspimpl.h
@@ -193,6 +193,11 @@ RTEMS_INLINE_ROUTINE MRSP_Status _MRSP_Wait_for_ownership(
   _Chain_Append_unprotected( &mrsp->Rivals, &rival.Node );
   _Resource_Add_rival( &mrsp->Resource, &executing->Resource_node );
   _Resource_Node_set_dependency( &executing->Resource_node, &mrsp->Resource );
+  _Scheduler_Help(
+    executing,
+    _Thread_Resource_node_to_thread( owner ),
+    SCHEDULER_HELP_ACTIVE
+  );
   _MRSP_Set_root( &executing->Resource_node, owner );
 
   if ( timeout > 0 ) {
@@ -231,11 +236,10 @@ RTEMS_INLINE_ROUTINE MRSP_Status _MRSP_Wait_for_ownership(
     mrsp->initial_priority_of_owner = initial_priority;
     status = MRSP_SUCCESSFUL;
   } else {
-    Resource_Node *executing_node = &executing->Resource_node;
-
-    _Resource_Node_extract( executing_node );
-    _Resource_Node_set_dependency( executing_node, NULL );
-    _MRSP_Set_root( executing_node, executing_node );
+    _Resource_Node_extract( &executing->Resource_node );
+    _Resource_Node_set_dependency( &executing->Resource_node, NULL );
+    _Scheduler_Help( executing, executing, SCHEDULER_HELP_YOURSELF );
+    _MRSP_Set_root( &executing->Resource_node, &executing->Resource_node );
     _MRSP_Restore_priority( mrsp, executing, initial_priority );
 
     status = MRSP_TIMEOUT;
@@ -321,13 +325,14 @@ RTEMS_INLINE_ROUTINE MRSP_Status _MRSP_Release(
     _Resource_Set_owner( &mrsp->Resource, NULL );
   } else {
     MRSP_Rival *rival = (MRSP_Rival *) _Chain_First( &mrsp->Rivals );
-    Resource_Node *new_owner = &rival->thread->Resource_node;
+    Thread_Control *new_owner = rival->thread;
 
-    _Resource_Node_extract( new_owner );
-    _Resource_Node_set_dependency( new_owner, NULL );
-    _Resource_Node_add_resource( new_owner, &mrsp->Resource );
-    _Resource_Set_owner( &mrsp->Resource, new_owner );
-    _MRSP_Set_root( new_owner, new_owner );
+    _Resource_Node_extract( &new_owner->Resource_node );
+    _Resource_Node_set_dependency( &new_owner->Resource_node, NULL );
+    _Resource_Node_add_resource( &new_owner->Resource_node, &mrsp->Resource );
+    _Resource_Set_owner( &mrsp->Resource, &new_owner->Resource_node );
+    _Scheduler_Help( new_owner, new_owner, SCHEDULER_HELP_YOURSELF );
+    _MRSP_Set_root( &new_owner->Resource_node, &new_owner->Resource_node );
     _MRSP_Add_state( rival, MRSP_RIVAL_STATE_NEW_OWNER );
   }
 
diff --git a/cpukit/score/include/rtems/score/scheduler.h b/cpukit/score/include/rtems/score/scheduler.h
index 918c6df..d9d21d3 100644
--- a/cpukit/score/include/rtems/score/scheduler.h
+++ b/cpukit/score/include/rtems/score/scheduler.h
@@ -161,6 +161,36 @@ struct Scheduler_Control {
   uint32_t name;
 };
 
+#if defined(RTEMS_SMP)
+/**
+ * @brief State to indicate potential help for other threads.
+ */
+typedef enum {
+  /**
+   * @brief This scheduler node is solely used by the owner.
+   *
+   * No help will be provided for other threads.
+   */
+  SCHEDULER_HELP_YOURSELF,
+
+  /**
+   * @brief This scheduler node can be used to help out threads.
+   *
+   * The owner thread is ready, but it will give away its processor in case
+   * there is a thread seeking for help.
+   */
+  SCHEDULER_HELP_ACTIVE,
+
+  /**
+   * @brief This scheduler node can be used to help out threads.
+   *
+   * The owner thread is blocked.  This scheduler node can be used by a thread
+   * seeking for help.
+   */
+  SCHEDULER_HELP_PASSIVE
+} Scheduler_Help_state;
+#endif
+
 /**
  * @brief Scheduler node for per-thread data.
  */
@@ -182,6 +212,16 @@ struct Scheduler_Node {
    * @brief The thread owning this node.
    */
   Thread_Control *owner;
+
+  /**
+   * @brief The thread using this node.
+   */
+  Thread_Control *user;
+
+  /**
+   * @brief The help state of this node.
+   */
+  Scheduler_Help_state help_state;
 #endif
 };
 
diff --git a/cpukit/score/include/rtems/score/schedulerimpl.h b/cpukit/score/include/rtems/score/schedulerimpl.h
index 391a8d7..f3284eb 100644
--- a/cpukit/score/include/rtems/score/schedulerimpl.h
+++ b/cpukit/score/include/rtems/score/schedulerimpl.h
@@ -659,6 +659,8 @@ RTEMS_INLINE_ROUTINE void _Scheduler_Node_do_initialize(
 {
 #if defined(RTEMS_SMP)
   node->owner = the_thread;
+  node->help_state = SCHEDULER_HELP_YOURSELF;
+  node->user = the_thread;
 #else
   (void) node;
   (void) the_thread;
@@ -672,6 +674,34 @@ RTEMS_INLINE_ROUTINE Thread_Control *_Scheduler_Node_get_owner(
 {
   return node->owner;
 }
+
+RTEMS_INLINE_ROUTINE Thread_Control *_Scheduler_Node_get_user(
+  const Scheduler_Node *node
+)
+{
+  return node->user;
+}
+
+/**
+ * @brief Helps a thread with respect to scheduling decisions.
+ *
+ * @param[in] helper The thread providing help.
+ * @param[in] needs_help The thread needing help.  It may be equal the thread
+ * providing help in case the help state is SCHEDULER_HELP_YOURSELF.
+ * @param[in] help_state The new help state.
+ */
+RTEMS_INLINE_ROUTINE void _Scheduler_Help(
+  Thread_Control       *helper,
+  Thread_Control       *needs_help,
+  Scheduler_Help_state  help_state
+)
+{
+  Scheduler_Node *node = _Scheduler_Node_get( helper );
+
+  node->help_state = help_state;
+
+  (void) needs_help;
+}
 #endif
 
 /** @} */
diff --git a/cpukit/score/include/rtems/score/threadimpl.h b/cpukit/score/include/rtems/score/threadimpl.h
index af24a3a..8ac831a 100644
--- a/cpukit/score/include/rtems/score/threadimpl.h
+++ b/cpukit/score/include/rtems/score/threadimpl.h
@@ -798,6 +798,16 @@ RTEMS_INLINE_ROUTINE bool _Thread_Owns_resources(
   return owns_resources;
 }
 
+#if defined(RTEMS_SMP)
+RTEMS_INLINE_ROUTINE Thread_Control *_Thread_Resource_node_to_thread(
+  Resource_Node *node
+)
+{
+  return (Thread_Control *)
+    ( (char *) node - offsetof( Thread_Control, Resource_node ) );
+}
+#endif
+
 RTEMS_INLINE_ROUTINE void _Thread_Debug_set_real_processor(
   Thread_Control  *the_thread,
   Per_CPU_Control *cpu
-- 
1.7.7