score: Add thread priority to scheduler nodes

The thread priority is manifest in two independent areas.  One area is
the user visible thread priority along with a potential thread queue.
The other is the scheduler.  Currently, a thread priority update via
_Thread_Change_priority() first updates the user visble thread priority
and the thread queue, then the scheduler is notified if necessary.  The
priority is passed to the scheduler via a local variable.  A generation
counter ensures that the scheduler discards out-of-date priorities.

This use of a local variable ties the update in these two areas close
together.  For later enhancements and the OMIP locking protocol
implementation we need more flexibility.  Add a thread priority
information block to Scheduler_Node and synchronize priority value
updates via a sequence lock on SMP configurations.

Update #2556.

1 files changed, 14 insertions, 16 deletions

diff --git a/cpukit/score/include/rtems/score/schedulerpriority.h b/cpukit/score/include/rtems/score/schedulerpriority.h
index d5e73c19fc..f2e045903e 100644
--- a/cpukit/score/include/rtems/score/schedulerpriority.h
+++ b/cpukit/score/include/rtems/score/schedulerpriority.h
@@ -44,13 +44,12 @@ extern "C" {
     _Scheduler_priority_Yield,            /* yield entry point */ \
     _Scheduler_priority_Block,            /* block entry point */ \
     _Scheduler_priority_Unblock,          /* unblock entry point */ \
-    _Scheduler_priority_Change_priority,  /* change priority entry point */ \
+    _Scheduler_priority_Update_priority,  /* update priority entry point */ \
     _Scheduler_default_Map_priority,      /* map priority entry point */ \
     _Scheduler_default_Unmap_priority,    /* unmap priority entry point */ \
     SCHEDULER_OPERATION_DEFAULT_ASK_FOR_HELP \
-    _Scheduler_default_Node_initialize,   /* node initialize entry point */ \
+    _Scheduler_priority_Node_initialize,  /* node initialize entry point */ \
     _Scheduler_default_Node_destroy,      /* node destroy entry point */ \
-    _Scheduler_priority_Update_priority,  /* update priority entry point */ \
     _Scheduler_default_Release_job,       /* new period of task */ \
     _Scheduler_default_Tick,              /* tick entry point */ \
     _Scheduler_default_Start_idle         /* start idle entry point */ \
@@ -78,6 +77,11 @@ typedef struct {
  * @brief Data for ready queue operations.
  */
 typedef struct {
+  /**
+   * @brief The thread priority currently used by the scheduler.
+   */
+  unsigned int current_priority;
+
   /** This field points to the Ready FIFO for this thread's priority. */
   Chain_Control                        *ready_chain;
 
@@ -134,16 +138,6 @@ void _Scheduler_priority_Schedule(
 );
 
 /**
- *  @brief Updates the scheduler node to reflect the new priority of the
- *  thread.
- */
-void _Scheduler_priority_Update_priority(
-  const Scheduler_Control *scheduler,
-  Thread_Control          *the_thread,
-  Priority_Control         new_priority
-);
-
-/**
  *  @brief Add @a the_thread to the scheduling decision.
  *
  *  This routine adds @a the_thread to the scheduling decision,
@@ -158,11 +152,15 @@ Scheduler_Void_or_thread _Scheduler_priority_Unblock(
   Thread_Control          *the_thread
 );
 
-Scheduler_Void_or_thread _Scheduler_priority_Change_priority(
+Scheduler_Void_or_thread _Scheduler_priority_Update_priority(
+  const Scheduler_Control *scheduler,
+  Thread_Control          *the_thread
+);
+
+void _Scheduler_priority_Node_initialize(
   const Scheduler_Control *scheduler,
   Thread_Control          *the_thread,
-  Priority_Control         new_priority,
-  bool                     prepend_it
+  Priority_Control         priority
 );
 
 /**