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, 4 insertions, 17 deletions

diff --git a/cpukit/score/src/mutex.c b/cpukit/score/src/mutex.c
index bfa36ff994..daa90a528f 100644
--- a/cpukit/score/src/mutex.c
+++ b/cpukit/score/src/mutex.c
@@ -128,33 +128,20 @@ static void _Mutex_Release_critical(
 )
 {
   Thread_queue_Heads *heads;
-  bool keep_priority;
 
+  heads = mutex->Queue.Queue.heads;
   mutex->Queue.Queue.owner = NULL;
-
   --executing->resource_count;
 
-  /*
-   * Ensure that the owner resource count is visible to all other
-   * processors and that we read the latest priority restore
-   * hint.
-   */
-  _Atomic_Fence( ATOMIC_ORDER_ACQ_REL );
-
-  heads = mutex->Queue.Queue.heads;
-  keep_priority = _Thread_Owns_resources( executing )
-    || !executing->priority_restore_hint;
-
-  if ( __predict_true( heads == NULL && keep_priority ) ) {
+  if ( __predict_true( heads == NULL ) ) {
     _Mutex_Queue_release( mutex, queue_context );
   } else {
     _Thread_queue_Surrender(
       &mutex->Queue.Queue,
-      MUTEX_TQ_OPERATIONS,
       heads,
       executing,
-      keep_priority,
-      queue_context
+      queue_context,
+      MUTEX_TQ_OPERATIONS
     );
   }
 }