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, 10 insertions, 44 deletions

diff --git a/cpukit/score/include/rtems/score/schedulerpriority.h b/cpukit/score/include/rtems/score/schedulerpriority.h
index 134dcd715b..b3c1466066 100644
--- a/cpukit/score/include/rtems/score/schedulerpriority.h
+++ b/cpukit/score/include/rtems/score/schedulerpriority.h
@@ -52,12 +52,10 @@ extern "C" {
     _Scheduler_priority_Yield,            /* yield entry point */ \
     _Scheduler_priority_Block,            /* block entry point */ \
     _Scheduler_priority_Unblock,          /* unblock entry point */ \
-    _Scheduler_default_Allocate,         /* allocate entry point */ \
-    _Scheduler_default_Free,             /* free entry point */ \
+    _Scheduler_priority_Change_priority,  /* change priority entry point */ \
+    _Scheduler_default_Allocate,          /* allocate entry point */ \
+    _Scheduler_default_Free,              /* free entry point */ \
     _Scheduler_priority_Update,           /* update entry point */ \
-    _Scheduler_priority_Enqueue,          /* enqueue entry point */ \
-    _Scheduler_priority_Enqueue_first,    /* enqueue_first entry point */ \
-    _Scheduler_priority_Extract,          /* extract entry point */ \
     _Scheduler_priority_Priority_compare, /* compares two priorities */ \
     _Scheduler_default_Release_job,       /* new period of task */ \
     _Scheduler_default_Tick,              /* tick entry point */ \
@@ -167,6 +165,13 @@ void _Scheduler_priority_Unblock(
   Thread_Control          *the_thread
 );
 
+void _Scheduler_priority_Change_priority(
+  const Scheduler_Control *scheduler,
+  Thread_Control          *the_thread,
+  Priority_Control         new_priority,
+  bool                     prepend_it
+);
+
 /**
  *  @brief The specified THREAD yields.
  *
@@ -192,45 +197,6 @@ void _Scheduler_priority_Yield(
 );
 
 /**
- *  @brief Puts @a the_thread on to the priority-based ready queue.
- *
- *  This routine puts @a the_thread on to the priority-based ready queue.
- *
- *  @param[in] the_thread will be enqueued at the TAIL of its priority.
- */
-void _Scheduler_priority_Enqueue(
-  const Scheduler_Control *scheduler,
-  Thread_Control          *the_thread
-);
-
-/**
- *  @brief Puts @a the_thread to the head of the ready queue.
- *
- *  This routine puts @a the_thread to the head of the ready queue.
- *  For priority-based ready queues, the thread will be the first thread
- *  at its priority level.
- *
- *  @param[in] the_thread will be enqueued at the HEAD of its priority.
- */
-void _Scheduler_priority_Enqueue_first(
-  const Scheduler_Control *scheduler,
-  Thread_Control          *the_thread
-);
-
-/**
- *  @brief Remove a specific thread from scheduler.
- *
- *  This routine removes a specific thread from the scheduler's set
- *  of ready threads.
- *
- *  @param[in] the_thread will be extracted from the ready set.
- */
-void _Scheduler_priority_Extract(
-  const Scheduler_Control *scheduler,
-  Thread_Control          *the_thread
-);
-
-/**
  *  @brief Compare two priorities.
  *
  *  This routine compares two priorities.