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, 0 insertions, 17 deletions

diff --git a/cpukit/score/include/rtems/score/statesimpl.h b/cpukit/score/include/rtems/score/statesimpl.h
index 00d1092dfb..4251b3c84d 100644
--- a/cpukit/score/include/rtems/score/statesimpl.h
+++ b/cpukit/score/include/rtems/score/statesimpl.h
@@ -42,8 +42,6 @@ extern "C" {
 #define STATES_DORMANT                         0x00001
 /** This macro corresponds to a task being suspended. */
 #define STATES_SUSPENDED                       0x00002
-/** This macro corresponds to a task being in an internal state transition. */
-#define STATES_TRANSIENT                       0x00004
 /** This macro corresponds to a task which is waiting for a timeout. */
 #define STATES_DELAYING                        0x00008
 /** This macro corresponds to a task waiting until a specific TOD. */
@@ -215,21 +213,6 @@ RTEMS_INLINE_ROUTINE bool _States_Is_suspended (
 }
 
 /**
- * This function returns true if the TRANSIENT state is set in
- * the_states, and false otherwise.
- *
- * @param[in] the_states is the task state set to test
- *
- * @return This method returns true if the desired state condition is set.
- */
-RTEMS_INLINE_ROUTINE bool _States_Is_transient (
-  States_Control the_states
-)
-{
-   return (the_states & STATES_TRANSIENT);
-}
-
-/**
  * This function returns true if the DELAYING state is set in
  * the_states, and false otherwise.
  *