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, 8 deletions

diff --git a/cpukit/score/include/rtems/score/mrsp.h b/cpukit/score/include/rtems/score/mrsp.h
index 08a2427492..5af3a06901 100644
--- a/cpukit/score/include/rtems/score/mrsp.h
+++ b/cpukit/score/include/rtems/score/mrsp.h
@@ -80,12 +80,9 @@ typedef struct {
   Thread_Control *thread;
 
   /**
-   * @brief The initial priority of the thread at the begin of the resource
-   * obtain sequence.
-   *
-   * Used to restore the priority after a release of this resource or timeout.
+   * @brief The ceiling priority used by the rival thread.
    */
-  Priority_Control initial_priority;
+  Priority_Node Ceiling_priority;
 
   /**
    * @brief The initial help state of the thread at the begin of the resource
@@ -135,10 +132,9 @@ struct MRSP_Control {
   Chain_Control Rivals;
 
   /**
-   * @brief The initial priority of the owner before it was elevated to the
-   * ceiling priority.
+   * @brief The ceiling priority used by the owner thread.
    */
-  Priority_Control initial_priority_of_owner;
+  Priority_Node Ceiling_priority;
 
   /**
    * @brief One ceiling priority per scheduler instance.