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, 7 insertions, 12 deletions

diff --git a/cpukit/score/include/rtems/score/schedulersimplesmp.h b/cpukit/score/include/rtems/score/schedulersimplesmp.h
index 1e712251c8..32e998d59a 100644
--- a/cpukit/score/include/rtems/score/schedulersimplesmp.h
+++ b/cpukit/score/include/rtems/score/schedulersimplesmp.h
@@ -63,13 +63,11 @@ typedef struct {
     _Scheduler_simple_SMP_Schedule, \
     _Scheduler_simple_SMP_Yield, \
     _Scheduler_simple_SMP_Block, \
-    _Scheduler_simple_SMP_Enqueue_priority_fifo, \
+    _Scheduler_simple_SMP_Unblock, \
+    _Scheduler_simple_SMP_Change_priority, \
     _Scheduler_simple_SMP_Allocate, \
     _Scheduler_default_Free, \
     _Scheduler_default_Update, \
-    _Scheduler_simple_SMP_Enqueue_priority_fifo, \
-    _Scheduler_simple_SMP_Enqueue_priority_lifo, \
-    _Scheduler_simple_SMP_Extract, \
     _Scheduler_priority_Priority_compare, \
     _Scheduler_default_Release_job, \
     _Scheduler_default_Tick, \
@@ -90,19 +88,16 @@ void _Scheduler_simple_SMP_Block(
   Thread_Control *thread
 );
 
-void _Scheduler_simple_SMP_Enqueue_priority_fifo(
+void _Scheduler_simple_SMP_Unblock(
   const Scheduler_Control *scheduler,
   Thread_Control *thread
 );
 
-void _Scheduler_simple_SMP_Enqueue_priority_lifo(
+void _Scheduler_simple_SMP_Change_priority(
   const Scheduler_Control *scheduler,
-  Thread_Control *thread
-);
-
-void _Scheduler_simple_SMP_Extract(
-  const Scheduler_Control *scheduler,
-  Thread_Control *thread
+  Thread_Control          *the_thread,
+  Priority_Control         new_priority,
+  bool                     prepend_it
 );
 
 void _Scheduler_simple_SMP_Yield(