[PATCH v2] score: PR2136: Fix _Thread_Change_priority()

Sebastian Huber sebastian.huber at embedded-brains.de
Fri Aug 9 07:35:47 UTC 2013 

Add call to _Scheduler_Schedule() in missing path after
_Thread_Set_transient() in _Thread_Change_priority().  See also
sptests/spintrcritical19.

Add thread parameter to _Scheduler_Schedule().  This parameter is
currently unused but may be used in future SMP schedulers.

Do heir selection in _Scheduler_Schedule().  Use
_Scheduler_Update_heir() for this in the particular scheduler
implementation.

Add and use _Scheduler_Generic_block().
---
 cpukit/score/Makefile.am                           |    1 +
 cpukit/score/include/rtems/score/scheduler.h       |    2 +-
 cpukit/score/include/rtems/score/scheduleredf.h    |    2 +-
 .../score/include/rtems/score/scheduleredfimpl.h   |   56 ++++++++++++++++++++
 cpukit/score/include/rtems/score/schedulerimpl.h   |   35 ++++++++++++-
 .../score/include/rtems/score/schedulerpriority.h  |    2 +-
 .../include/rtems/score/schedulerpriorityimpl.h    |   12 ++++-
 cpukit/score/include/rtems/score/schedulersimple.h |    2 +-
 .../include/rtems/score/schedulersimpleimpl.h      |   16 +++++-
 .../score/include/rtems/score/schedulersimplesmp.h |    2 +-
 cpukit/score/include/rtems/score/threadimpl.h      |   10 ----
 cpukit/score/preinstall.am                         |    4 ++
 cpukit/score/src/scheduleredfblock.c               |   17 ++----
 cpukit/score/src/scheduleredfschedule.c            |   12 +---
 cpukit/score/src/scheduleredfyield.c               |    9 +---
 cpukit/score/src/schedulerpriorityblock.c          |   16 ++----
 cpukit/score/src/schedulerpriorityschedule.c       |    4 +-
 cpukit/score/src/schedulersimpleblock.c            |   15 ++---
 cpukit/score/src/schedulersimpleschedule.c         |    9 +--
 cpukit/score/src/schedulersimplesmp.c              |    4 +-
 cpukit/score/src/schedulersimpleyield.c            |    5 +--
 cpukit/score/src/threadchangepriority.c            |   14 ++++--
 22 files changed, 164 insertions(+), 85 deletions(-)
 create mode 100644 cpukit/score/include/rtems/score/scheduleredfimpl.h

diff --git a/cpukit/score/Makefile.am b/cpukit/score/Makefile.am
index f3f76c5..584c53d 100644
--- a/cpukit/score/Makefile.am
+++ b/cpukit/score/Makefile.am
@@ -50,6 +50,7 @@ include_rtems_score_HEADERS += include/rtems/score/scheduler.h
 include_rtems_score_HEADERS += include/rtems/score/schedulerimpl.h
 include_rtems_score_HEADERS += include/rtems/score/schedulercbs.h
 include_rtems_score_HEADERS += include/rtems/score/scheduleredf.h
+include_rtems_score_HEADERS += include/rtems/score/scheduleredfimpl.h
 include_rtems_score_HEADERS += include/rtems/score/schedulerpriority.h
 include_rtems_score_HEADERS += include/rtems/score/schedulerpriorityimpl.h
 include_rtems_score_HEADERS += include/rtems/score/schedulerprioritysmp.h
diff --git a/cpukit/score/include/rtems/score/scheduler.h b/cpukit/score/include/rtems/score/scheduler.h
index a34387d..10a2a97 100644
--- a/cpukit/score/include/rtems/score/scheduler.h
+++ b/cpukit/score/include/rtems/score/scheduler.h
@@ -46,7 +46,7 @@ typedef struct {
   void ( *initialize )(void);
 
   /** Implements the scheduling decision logic (policy). */
-  void ( *schedule )(void);
+  void ( *schedule )( Thread_Control *thread );
 
   /**
    * @brief Voluntarily yields the processor per the scheduling policy.
diff --git a/cpukit/score/include/rtems/score/scheduleredf.h b/cpukit/score/include/rtems/score/scheduleredf.h
index b28bed1..01f91e6 100644
--- a/cpukit/score/include/rtems/score/scheduleredf.h
+++ b/cpukit/score/include/rtems/score/scheduleredf.h
@@ -129,7 +129,7 @@ void _Scheduler_EDF_Block(
  *  This kernel routine sets the heir thread to be the next ready thread
  *  in the rbtree ready queue.
  */
-void _Scheduler_EDF_Schedule( void );
+void _Scheduler_EDF_Schedule( Thread_Control *thread );
 
 /**
  *  @brief Allocates EDF specific information of @a the_thread.
diff --git a/cpukit/score/include/rtems/score/scheduleredfimpl.h b/cpukit/score/include/rtems/score/scheduleredfimpl.h
new file mode 100644
index 0000000..04201bc
--- /dev/null
+++ b/cpukit/score/include/rtems/score/scheduleredfimpl.h
@@ -0,0 +1,56 @@
+/**
+ * @file
+ *
+ * @ingroup ScoreSchedulerEDF
+ *
+ * @brief EDF Scheduler Implementation
+ */
+
+/*
+ *  Copryight (c) 2011 Petr Benes.
+ *  Copyright (C) 2011 On-Line Applications Research Corporation (OAR).
+ *
+ *  The license and distribution terms for this file may be
+ *  found in the file LICENSE in this distribution or at
+ *  http://www.rtems.com/license/LICENSE.
+ */
+
+#ifndef _RTEMS_SCORE_SCHEDULEREDFIMPL_H
+#define _RTEMS_SCORE_SCHEDULEREDFIMPL_H
+
+#include <rtems/score/scheduleredf.h>
+#include <rtems/score/schedulerimpl.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/**
+ * @addtogroup ScoreSchedulerEDF EDF
+ *
+ * @{
+ */
+
+RTEMS_INLINE_ROUTINE void _Scheduler_EDF_Schedule_body(
+  Thread_Control *thread,
+  bool force_dispatch
+)
+{
+  RBTree_Node *first = _RBTree_First(&_Scheduler_EDF_Ready_queue, RBT_LEFT);
+  Scheduler_EDF_Per_thread *sched_info =
+    _RBTree_Container_of(first, Scheduler_EDF_Per_thread, Node);
+  Thread_Control *heir = (Thread_Control *) sched_info->thread;
+
+  ( void ) thread;
+
+  _Scheduler_Update_heir( heir, force_dispatch );
+}
+
+/**@}*/
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif
+/* end of include file */
diff --git a/cpukit/score/include/rtems/score/schedulerimpl.h b/cpukit/score/include/rtems/score/schedulerimpl.h
index 5ea4bb8..2d9957a 100644
--- a/cpukit/score/include/rtems/score/schedulerimpl.h
+++ b/cpukit/score/include/rtems/score/schedulerimpl.h
@@ -20,6 +20,7 @@
 #define _RTEMS_SCORE_SCHEDULERIMPL_H
 
 #include <rtems/score/scheduler.h>
+#include <rtems/score/threadimpl.h>
 
 #ifdef __cplusplus
 extern "C" {
@@ -59,10 +60,12 @@ void _Scheduler_Handler_initialization( void );
  *
  * This kernel routine implements the scheduling decision logic for
  * the scheduler. It does NOT dispatch.
+ *
+ * @param[in] thread The thread which state changed previously.
  */
-RTEMS_INLINE_ROUTINE void _Scheduler_Schedule( void )
+RTEMS_INLINE_ROUTINE void _Scheduler_Schedule( Thread_Control *thread )
 {
-  _Scheduler.Operations.schedule();
+  _Scheduler.Operations.schedule( thread );
 }
 
 /**
@@ -237,6 +240,34 @@ RTEMS_INLINE_ROUTINE void _Scheduler_Start_idle(
   ( *_Scheduler.Operations.start_idle )( thread, processor );
 }
 
+RTEMS_INLINE_ROUTINE void _Scheduler_Update_heir(
+  Thread_Control *heir,
+  bool force_dispatch
+)
+{
+  Thread_Control *executing = _Thread_Executing;
+
+  _Thread_Heir = heir;
+
+  if ( executing != heir && ( force_dispatch || executing->is_preemptible ) )
+    _Thread_Dispatch_necessary = true;
+}
+
+RTEMS_INLINE_ROUTINE void _Scheduler_Generic_block(
+  void ( *extract )( Thread_Control *thread ),
+  void ( *schedule )( Thread_Control *thread, bool force_dispatch ),
+  Thread_Control *thread
+)
+{
+  ( *extract )( thread );
+
+  /* TODO: flash critical section? */
+
+  if ( _Thread_Is_executing( thread ) || _Thread_Is_heir( thread ) ) {
+    ( *schedule )( thread, true );
+  }
+}
+
 /**
  * Macro testing whether @a p1 has lower priority than @a p2
  * in the intuitive sense of priority.
diff --git a/cpukit/score/include/rtems/score/schedulerpriority.h b/cpukit/score/include/rtems/score/schedulerpriority.h
index 6964943..cbe0066 100644
--- a/cpukit/score/include/rtems/score/schedulerpriority.h
+++ b/cpukit/score/include/rtems/score/schedulerpriority.h
@@ -93,7 +93,7 @@ void _Scheduler_priority_Block(
  *  This kernel routine sets the heir thread to be the next ready thread
  *  by invoking the_scheduler->ready_queue->operations->first().
  */
-void _Scheduler_priority_Schedule(void);
+void _Scheduler_priority_Schedule( Thread_Control *thread );
 
 /**
  *  @brief Allocates @a the_thread->scheduler.
diff --git a/cpukit/score/include/rtems/score/schedulerpriorityimpl.h b/cpukit/score/include/rtems/score/schedulerpriorityimpl.h
index b69a910..6c57952 100644
--- a/cpukit/score/include/rtems/score/schedulerpriorityimpl.h
+++ b/cpukit/score/include/rtems/score/schedulerpriorityimpl.h
@@ -23,6 +23,7 @@
 #include <rtems/score/schedulerpriority.h>
 #include <rtems/score/chainimpl.h>
 #include <rtems/score/prioritybitmapimpl.h>
+#include <rtems/score/schedulerimpl.h>
 #include <rtems/score/thread.h>
 #include <rtems/score/wkspace.h>
 
@@ -188,11 +189,18 @@ RTEMS_INLINE_ROUTINE void _Scheduler_priority_Ready_queue_requeue(
  * This kernel routine implements scheduling decision logic
  * for priority-based scheduling.
  */
-RTEMS_INLINE_ROUTINE void _Scheduler_priority_Schedule_body(void)
+RTEMS_INLINE_ROUTINE void _Scheduler_priority_Schedule_body(
+  Thread_Control *thread,
+  bool force_dispatch
+)
 {
-  _Thread_Heir = _Scheduler_priority_Ready_queue_first(
+  Thread_Control *heir = _Scheduler_priority_Ready_queue_first(
     (Chain_Control *) _Scheduler.information
   );
+
+  ( void ) thread;
+
+  _Scheduler_Update_heir( heir, force_dispatch );
 }
 
 /**
diff --git a/cpukit/score/include/rtems/score/schedulersimple.h b/cpukit/score/include/rtems/score/schedulersimple.h
index 5180d36..477ea2c 100644
--- a/cpukit/score/include/rtems/score/schedulersimple.h
+++ b/cpukit/score/include/rtems/score/schedulersimple.h
@@ -66,7 +66,7 @@ void _Scheduler_simple_Initialize( void );
  *  on the ready queue by getting the first node in the scheduler
  *  information.
  */
-void _Scheduler_simple_Schedule( void );
+void _Scheduler_simple_Schedule( Thread_Control *thread );
 
 /**
  *  @brief Invoked when a thread wishes to voluntarily
diff --git a/cpukit/score/include/rtems/score/schedulersimpleimpl.h b/cpukit/score/include/rtems/score/schedulersimpleimpl.h
index 076d1a9..51d3774 100644
--- a/cpukit/score/include/rtems/score/schedulersimpleimpl.h
+++ b/cpukit/score/include/rtems/score/schedulersimpleimpl.h
@@ -21,7 +21,7 @@
 
 #include <rtems/score/schedulersimple.h>
 #include <rtems/score/chainimpl.h>
-#include <rtems/score/thread.h>
+#include <rtems/score/schedulerimpl.h>
 
 #ifdef __cplusplus
 extern "C" {
@@ -96,6 +96,20 @@ RTEMS_INLINE_ROUTINE void _Scheduler_simple_Insert_priority_fifo(
   );
 }
 
+RTEMS_INLINE_ROUTINE void _Scheduler_simple_Schedule_body(
+  Thread_Control *thread,
+  bool force_dispatch
+)
+{
+  Thread_Control *heir = (Thread_Control *) _Chain_First(
+    (Chain_Control *) _Scheduler.information
+  );
+
+  ( void ) thread;
+
+  _Scheduler_Update_heir( heir, force_dispatch );
+}
+
 /** @} */
 
 #ifdef __cplusplus
diff --git a/cpukit/score/include/rtems/score/schedulersimplesmp.h b/cpukit/score/include/rtems/score/schedulersimplesmp.h
index 1b827cb..6cc87f3 100644
--- a/cpukit/score/include/rtems/score/schedulersimplesmp.h
+++ b/cpukit/score/include/rtems/score/schedulersimplesmp.h
@@ -85,7 +85,7 @@ void _Scheduler_simple_smp_Extract( Thread_Control *thread );
 
 void _Scheduler_simple_smp_Yield( Thread_Control *thread );
 
-void _Scheduler_simple_smp_Schedule( void );
+void _Scheduler_simple_smp_Schedule( Thread_Control *thread );
 
 void _Scheduler_simple_smp_Start_idle(
   Thread_Control *thread,
diff --git a/cpukit/score/include/rtems/score/threadimpl.h b/cpukit/score/include/rtems/score/threadimpl.h
index 06d4ee6..a3b6904 100644
--- a/cpukit/score/include/rtems/score/threadimpl.h
+++ b/cpukit/score/include/rtems/score/threadimpl.h
@@ -498,16 +498,6 @@ RTEMS_INLINE_ROUTINE bool _Thread_Is_heir (
 }
 
 /**
- * This function returns true if the currently executing thread
- * is also the heir thread, and false otherwise.
- */
-
-RTEMS_INLINE_ROUTINE bool _Thread_Is_executing_also_the_heir( void )
-{
-  return ( _Thread_Executing == _Thread_Heir );
-}
-
-/**
  * This routine clears any blocking state for the_thread.  It performs
  * any necessary scheduling operations including the selection of
  * a new heir thread.
diff --git a/cpukit/score/preinstall.am b/cpukit/score/preinstall.am
index 509d1dd..e79b8bb 100644
--- a/cpukit/score/preinstall.am
+++ b/cpukit/score/preinstall.am
@@ -183,6 +183,10 @@ $(PROJECT_INCLUDE)/rtems/score/scheduleredf.h: include/rtems/score/scheduleredf.
 	$(INSTALL_DATA) $< $(PROJECT_INCLUDE)/rtems/score/scheduleredf.h
 PREINSTALL_FILES += $(PROJECT_INCLUDE)/rtems/score/scheduleredf.h
 
+$(PROJECT_INCLUDE)/rtems/score/scheduleredfimpl.h: include/rtems/score/scheduleredfimpl.h $(PROJECT_INCLUDE)/rtems/score/$(dirstamp)
+	$(INSTALL_DATA) $< $(PROJECT_INCLUDE)/rtems/score/scheduleredfimpl.h
+PREINSTALL_FILES += $(PROJECT_INCLUDE)/rtems/score/scheduleredfimpl.h
+
 $(PROJECT_INCLUDE)/rtems/score/schedulerpriority.h: include/rtems/score/schedulerpriority.h $(PROJECT_INCLUDE)/rtems/score/$(dirstamp)
 	$(INSTALL_DATA) $< $(PROJECT_INCLUDE)/rtems/score/schedulerpriority.h
 PREINSTALL_FILES += $(PROJECT_INCLUDE)/rtems/score/schedulerpriority.h
diff --git a/cpukit/score/src/scheduleredfblock.c b/cpukit/score/src/scheduleredfblock.c
index 4ad767d..80bb1d5 100644
--- a/cpukit/score/src/scheduleredfblock.c
+++ b/cpukit/score/src/scheduleredfblock.c
@@ -19,20 +19,15 @@
 #include "config.h"
 #endif
 
-#include <rtems/score/scheduleredf.h>
-#include <rtems/score/threadimpl.h>
+#include <rtems/score/scheduleredfimpl.h>
 
 void _Scheduler_EDF_Block(
   Thread_Control    *the_thread
 )
 {
-  _Scheduler_EDF_Extract( the_thread );
-
-  /* TODO: flash critical section? */
-
-  if ( _Thread_Is_heir( the_thread ) )
-    _Scheduler_EDF_Schedule();
-
-  if ( _Thread_Is_executing( the_thread ) )
-    _Thread_Dispatch_necessary = true;
+  _Scheduler_Generic_block(
+    _Scheduler_EDF_Extract,
+    _Scheduler_EDF_Schedule_body,
+    the_thread
+  );
 }
diff --git a/cpukit/score/src/scheduleredfschedule.c b/cpukit/score/src/scheduleredfschedule.c
index dbe21dc..a71a5b5 100644
--- a/cpukit/score/src/scheduleredfschedule.c
+++ b/cpukit/score/src/scheduleredfschedule.c
@@ -18,15 +18,9 @@
 #include "config.h"
 #endif
 
-#include <rtems/system.h>
-#include <rtems/score/scheduler.h>
-#include <rtems/score/scheduleredf.h>
+#include <rtems/score/scheduleredfimpl.h>
 
-void _Scheduler_EDF_Schedule(void)
+void _Scheduler_EDF_Schedule( Thread_Control *thread )
 {
-  RBTree_Node *first = _RBTree_First(&_Scheduler_EDF_Ready_queue, RBT_LEFT);
-  Scheduler_EDF_Per_thread *sched_info =
-    _RBTree_Container_of(first, Scheduler_EDF_Per_thread, Node);
-
-  _Thread_Heir = (Thread_Control *) sched_info->thread;
+  _Scheduler_EDF_Schedule_body( thread, false );
 }
diff --git a/cpukit/score/src/scheduleredfyield.c b/cpukit/score/src/scheduleredfyield.c
index 4ba9f79..fc5b13a 100644
--- a/cpukit/score/src/scheduleredfyield.c
+++ b/cpukit/score/src/scheduleredfyield.c
@@ -19,11 +19,7 @@
 #include "config.h"
 #endif
 
-#include <rtems/system.h>
-#include <rtems/score/isr.h>
-#include <rtems/score/scheduler.h>
-#include <rtems/score/scheduleredf.h>
-#include <rtems/score/thread.h>
+#include <rtems/score/scheduleredfimpl.h>
 
 void _Scheduler_EDF_Yield( Thread_Control *thread )
 {
@@ -44,8 +40,7 @@ void _Scheduler_EDF_Yield( Thread_Control *thread )
 
   _ISR_Flash( level );
 
-  _Scheduler_EDF_Schedule();
-  _Thread_Dispatch_necessary = true;
+  _Scheduler_EDF_Schedule_body( thread, false );
 
   _ISR_Enable( level );
 }
diff --git a/cpukit/score/src/schedulerpriorityblock.c b/cpukit/score/src/schedulerpriorityblock.c
index 9e48101..329ddd7 100644
--- a/cpukit/score/src/schedulerpriorityblock.c
+++ b/cpukit/score/src/schedulerpriorityblock.c
@@ -21,20 +21,14 @@
 #endif
 
 #include <rtems/score/schedulerpriorityimpl.h>
-#include <rtems/score/threadimpl.h>
 
 void _Scheduler_priority_Block(
   Thread_Control   *the_thread
 )
 {
-  _Scheduler_priority_Ready_queue_extract( the_thread );
-
-  /* TODO: flash critical section? */
-
-  if ( _Thread_Is_heir( the_thread ) )
-     _Scheduler_priority_Schedule_body();
-
-  if ( _Thread_Is_executing( the_thread ) )
-    _Thread_Dispatch_necessary = true;
-
+  _Scheduler_Generic_block(
+    _Scheduler_priority_Ready_queue_extract,
+    _Scheduler_priority_Schedule_body,
+    the_thread
+  );
 }
diff --git a/cpukit/score/src/schedulerpriorityschedule.c b/cpukit/score/src/schedulerpriorityschedule.c
index 22ed5f4..42647e6 100644
--- a/cpukit/score/src/schedulerpriorityschedule.c
+++ b/cpukit/score/src/schedulerpriorityschedule.c
@@ -20,7 +20,7 @@
 
 #include <rtems/score/schedulerpriorityimpl.h>
 
-void _Scheduler_priority_Schedule(void)
+void _Scheduler_priority_Schedule( Thread_Control *thread )
 {
-  _Scheduler_priority_Schedule_body();
+  _Scheduler_priority_Schedule_body( thread, false );
 }
diff --git a/cpukit/score/src/schedulersimpleblock.c b/cpukit/score/src/schedulersimpleblock.c
index b9753b5..1e6e8a0 100644
--- a/cpukit/score/src/schedulersimpleblock.c
+++ b/cpukit/score/src/schedulersimpleblock.c
@@ -19,18 +19,15 @@
 #include "config.h"
 #endif
 
-#include <rtems/score/schedulersimple.h>
-#include <rtems/score/threadimpl.h>
+#include <rtems/score/schedulersimpleimpl.h>
 
 void _Scheduler_simple_Block(
   Thread_Control   *the_thread
 )
 {
-  _Scheduler_simple_Extract(the_thread);
-
-  if ( _Thread_Is_heir( the_thread ) )
-    _Scheduler_simple_Schedule();
-
-  if ( _Thread_Is_executing( the_thread ) )
-    _Thread_Dispatch_necessary = true;
+  _Scheduler_Generic_block(
+    _Scheduler_simple_Extract,
+    _Scheduler_simple_Schedule_body,
+    the_thread
+  );
 }
diff --git a/cpukit/score/src/schedulersimpleschedule.c b/cpukit/score/src/schedulersimpleschedule.c
index b60f096..5018e0b 100644
--- a/cpukit/score/src/schedulersimpleschedule.c
+++ b/cpukit/score/src/schedulersimpleschedule.c
@@ -18,12 +18,9 @@
 #include "config.h"
 #endif
 
-#include <rtems/score/schedulersimple.h>
-#include <rtems/score/chainimpl.h>
+#include <rtems/score/schedulersimpleimpl.h>
 
-void _Scheduler_simple_Schedule(void)
+void _Scheduler_simple_Schedule( Thread_Control *thread )
 {
-  _Thread_Heir = (Thread_Control *) _Chain_First(
-    (Chain_Control *) _Scheduler.information
-  );
+  _Scheduler_simple_Schedule_body( thread, false );
 }
diff --git a/cpukit/score/src/schedulersimplesmp.c b/cpukit/score/src/schedulersimplesmp.c
index db08b96..e261510 100644
--- a/cpukit/score/src/schedulersimplesmp.c
+++ b/cpukit/score/src/schedulersimplesmp.c
@@ -182,9 +182,9 @@ void _Scheduler_simple_smp_Yield( Thread_Control *thread )
   _ISR_Enable( level );
 }
 
-void _Scheduler_simple_smp_Schedule( void )
+void _Scheduler_simple_smp_Schedule( Thread_Control *thread )
 {
-  /* Nothing to do */
+  ( void ) thread;
 }
 
 void _Scheduler_simple_smp_Start_idle(
diff --git a/cpukit/score/src/schedulersimpleyield.c b/cpukit/score/src/schedulersimpleyield.c
index cb8dc6f..43784d6 100644
--- a/cpukit/score/src/schedulersimpleyield.c
+++ b/cpukit/score/src/schedulersimpleyield.c
@@ -32,10 +32,7 @@ void _Scheduler_simple_Yield( Thread_Control *thread )
 
     _ISR_Flash( level );
 
-    _Scheduler_simple_Schedule();
-
-    if ( !_Thread_Is_heir( thread ) )
-      _Thread_Dispatch_necessary = true;
+    _Scheduler_simple_Schedule_body( thread, false );
 
   _ISR_Enable( level );
 }
diff --git a/cpukit/score/src/threadchangepriority.c b/cpukit/score/src/threadchangepriority.c
index b443731..b3d7984 100644
--- a/cpukit/score/src/threadchangepriority.c
+++ b/cpukit/score/src/threadchangepriority.c
@@ -62,6 +62,15 @@ void _Thread_Change_priority(
     /* Only clear the transient state if it wasn't set already */
     if ( ! _States_Is_transient( original_state ) )
       the_thread->current_state = _States_Clear( STATES_TRANSIENT, state );
+
+    /*
+     * The thread may have new blocking states added by interrupt service
+     * routines after the change into the transient state.  This will not
+     * result in a _Scheduler_Block() operation.  Make sure we select an heir
+     * now.
+     */
+    _Scheduler_Schedule( the_thread );
+
     _ISR_Enable( level );
     if ( _States_Is_waiting_on_thread_queue( state ) ) {
       _Thread_queue_Requeue( the_thread->Wait.queue, the_thread );
@@ -91,10 +100,7 @@ void _Thread_Change_priority(
    *  We altered the set of thread priorities.  So let's figure out
    *  who is the heir and if we need to switch to them.
    */
-  _Scheduler_Schedule();
+  _Scheduler_Schedule( the_thread );
 
-  if ( !_Thread_Is_executing_also_the_heir() &&
-       _Thread_Executing->is_preemptible )
-    _Thread_Dispatch_necessary = true;
   _ISR_Enable( level );
 }
-- 
1.7.7

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