score: Simplify _Thread_Change_priority()

The function to change a thread priority was too complex.  Simplify it
with a new scheduler operation.  This increases the average case
performance due to the simplified logic.  The interrupt disabled
critical section is a bit prolonged since now the extract, update and
enqueue steps are executed atomically.  This should however not impact
the worst-case interrupt latency since at least for the Deterministic
Priority Scheduler this sequence can be carried out with a wee bit of
instructions and no loops.

Add _Scheduler_Change_priority() to replace the sequence of
  - _Thread_Set_transient(),
  - _Scheduler_Extract(),
  - _Scheduler_Enqueue(), and
  - _Scheduler_Enqueue_first().

Delete STATES_TRANSIENT, _States_Is_transient() and
_Thread_Set_transient() since this state is now superfluous.

With this change it is possible to get rid of the
SCHEDULER_SMP_NODE_IN_THE_AIR state.  This considerably simplifies the
implementation of the new SMP locking protocols.

1 files changed, 29 insertions, 41 deletions

diff --git a/cpukit/score/include/rtems/score/schedulerimpl.h b/cpukit/score/include/rtems/score/schedulerimpl.h
index 2129493b0a..f37a3553ff 100644
--- a/cpukit/score/include/rtems/score/schedulerimpl.h
+++ b/cpukit/score/include/rtems/score/schedulerimpl.h
@@ -144,6 +144,35 @@ RTEMS_INLINE_ROUTINE void _Scheduler_Unblock(
 }
 
 /**
+ * @brief Propagates a priority change of a thread to the scheduler.
+ *
+ * The caller must ensure that the thread is in the ready state.  The caller
+ * must ensure that the priority value actually changed and is not equal to the
+ * current priority value.
+ *
+ * @param[in] scheduler The scheduler instance.
+ * @param[in] the_thread The thread changing its priority.
+ * @param[in] new_priority The new thread priority.
+ * @param[in] prepend_it In case this is true, then enqueue the thread as the
+ * first of its priority group, otherwise enqueue the thread as the last of its
+ * priority group.
+ */
+RTEMS_INLINE_ROUTINE void _Scheduler_Change_priority(
+  const Scheduler_Control *scheduler,
+  Thread_Control          *the_thread,
+  Priority_Control         new_priority,
+  bool                     prepend_it
+)
+{
+  ( *scheduler->Operations.change_priority )(
+    scheduler,
+    the_thread,
+    new_priority,
+    prepend_it
+  );
+}
+
+/**
  * @brief Scheduler allocate.
  *
  * This routine allocates @a the_thread->scheduler
@@ -183,47 +212,6 @@ RTEMS_INLINE_ROUTINE void _Scheduler_Update(
 }
 
 /**
- * @brief Enqueues a thread as the last of its priority group.
- *
- * @param[in] scheduler The scheduler instance.
- * @param[in] the_thread The thread to enqueue.
- */
-RTEMS_INLINE_ROUTINE void _Scheduler_Enqueue(
-  const Scheduler_Control *scheduler,
-  Thread_Control          *the_thread
-)
-{
-  ( *scheduler->Operations.enqueue )( scheduler, the_thread );
-}
-
-/**
- * @brief Enqueues a thread as the first of its priority group.
- *
- * @param[in] scheduler The scheduler instance.
- * @param[in] the_thread The thread to enqueue.
- */
-RTEMS_INLINE_ROUTINE void _Scheduler_Enqueue_first(
-  const Scheduler_Control *scheduler,
-  Thread_Control          *the_thread
-)
-{
-  ( *scheduler->Operations.enqueue_first )( scheduler, the_thread );
-}
-
-/**
- * @brief Scheduler extract.
- *
- * This routine extract @a the_thread->scheduler
- */
-RTEMS_INLINE_ROUTINE void _Scheduler_Extract(
-  const Scheduler_Control *scheduler,
-  Thread_Control          *the_thread
-)
-{
-  ( *scheduler->Operations.extract )( scheduler, the_thread );
-}
-
-/**
  * @brief Compares two priority values.
  *
  * @param[in] scheduler The scheduler instance.