score: Rework thread priority management

Add priority nodes which contribute to the overall thread priority.

The actual priority of a thread is now an aggregation of priority nodes.
The thread priority aggregation for the home scheduler instance of a
thread consists of at least one priority node, which is normally the
real priority of the thread.  The locking protocols (e.g. priority
ceiling and priority inheritance), rate-monotonic period objects and the
POSIX sporadic server add, change and remove priority nodes.

A thread changes its priority now immediately, e.g. priority changes are
not deferred until the thread releases its last resource.

Replace the _Thread_Change_priority() function with

 * _Thread_Priority_perform_actions(),
 * _Thread_Priority_add(),
 * _Thread_Priority_remove(),
 * _Thread_Priority_change(), and
 * _Thread_Priority_update().

Update #2412.
Update #2556.

1 files changed, 2 insertions, 6 deletions

diff --git a/cpukit/score/src/scheduleredfchangepriority.c b/cpukit/score/src/scheduleredfchangepriority.c
index 9a73128e4c..8940b1d54b 100644
--- a/cpukit/score/src/scheduleredfchangepriority.c
+++ b/cpukit/score/src/scheduleredfchangepriority.c
@@ -54,16 +54,12 @@ Scheduler_Void_or_thread _Scheduler_EDF_Update_priority(
   node = _Scheduler_EDF_Thread_get_node( the_thread );
   priority = _Scheduler_Node_get_priority( &node->Base, &prepend_it );
 
-  if ( priority == node->current_priority ) {
+  if ( priority == node->priority ) {
     /* Nothing to do */
     SCHEDULER_RETURN_VOID_OR_NULL;
   }
 
-  if ( ( priority & SCHEDULER_EDF_PRIO_MSB ) != 0 ) {
-    node->background_priority = priority;
-  }
-
-  node->current_priority = priority;
+  node->priority = priority;
   context = _Scheduler_EDF_Get_context( scheduler );
 
   _Scheduler_EDF_Extract( context, node );