2010-06-28 Joel Sherrill <joel.sherrill@oarcorp.com>

	PR 1573/cpukit
	* configure.ac, posix/src/killinfo.c,
	posix/src/psignalclearprocesssignals.c,
	posix/src/psignalsetprocesssignals.c,
	posix/src/psignalunblockthread.c, posix/src/pthreadcreate.c,
	posix/src/pthreadkill.c, posix/src/pthreadsigmask.c,
	rtems/src/signalsend.c, rtems/src/taskmode.c, score/Makefile.am,
	score/preinstall.am, score/include/rtems/system.h,
	score/include/rtems/score/context.h, score/include/rtems/score/isr.h,
	score/include/rtems/score/thread.h, score/src/isr.c,
	score/src/isrthreaddispatch.c, score/src/thread.c,
	score/src/threaddispatch.c, score/src/threadloadenv.c: Add a per cpu
	data structure which contains the information required by RTEMS for
	each CPU core. This encapsulates information such as thread
	executing, heir, idle and dispatch needed.
	* score/include/rtems/score/percpu.h, score/src/percpu.c: New files.

24 files changed, 272 insertions, 111 deletions

diff --git a/cpukit/ChangeLog b/cpukit/ChangeLog
index e654ec3b71..726bf953bf 100644
--- a/cpukit/ChangeLog
+++ b/cpukit/ChangeLog
@@ -1,5 +1,24 @@
 2010-06-28	Joel Sherrill <joel.sherrill@oarcorp.com>
 
+	PR 1573/cpukit
+	* configure.ac, posix/src/killinfo.c,
+	posix/src/psignalclearprocesssignals.c,
+	posix/src/psignalsetprocesssignals.c,
+	posix/src/psignalunblockthread.c, posix/src/pthreadcreate.c,
+	posix/src/pthreadkill.c, posix/src/pthreadsigmask.c,
+	rtems/src/signalsend.c, rtems/src/taskmode.c, score/Makefile.am,
+	score/preinstall.am, score/include/rtems/system.h,
+	score/include/rtems/score/context.h, score/include/rtems/score/isr.h,
+	score/include/rtems/score/thread.h, score/src/isr.c,
+	score/src/isrthreaddispatch.c, score/src/thread.c,
+	score/src/threaddispatch.c, score/src/threadloadenv.c: Add a per cpu
+	data structure which contains the information required by RTEMS for
+	each CPU core. This encapsulates information such as thread
+	executing, heir, idle and dispatch needed.
+	* score/include/rtems/score/percpu.h, score/src/percpu.c: New files.
+
+2010-06-28	Joel Sherrill <joel.sherrill@oarcorp.com>
+
 	* libcsupport/src/libio_sockets.c: Use
 	rtems_set_errno_and_return_minus_one() where it was missed before.
 
diff --git a/cpukit/configure.ac b/cpukit/configure.ac
index 116bc6c791..d74c424210 100644
--- a/cpukit/configure.ac
+++ b/cpukit/configure.ac
@@ -251,6 +251,9 @@ AC_CHECK_DECLS([sbrk],,,[#include <unistd.h>])
 ## Check if libc provides BSD's strlcpy/strlcat
 AC_CHECK_FUNCS(strlcpy strlcat)
 
+## This is needed to generate the field offsets of the per CPU 
+## data structure so they can be accessed from assembly code.
+AC_CHECK_SIZEOF([void *])
 
 # ... far too many conditionals ...
 AM_CONDITIONAL(LIBRPC,[test x"$rtems_cv_HAS_NETWORKING" = x"yes"])
diff --git a/cpukit/posix/src/killinfo.c b/cpukit/posix/src/killinfo.c
index c02f7807e6..2ae5857a6f 100644
--- a/cpukit/posix/src/killinfo.c
+++ b/cpukit/posix/src/killinfo.c
@@ -314,8 +314,6 @@ int killinfo(
    */
 process_it:
 
-  the_thread->do_post_task_switch_extension = true;
-
   /*
    *  Returns true if the signal was synchronously given to a thread
    *  blocked waiting for the signal.
diff --git a/cpukit/posix/src/psignalclearprocesssignals.c b/cpukit/posix/src/psignalclearprocesssignals.c
index a601fa2406..b11ae0ebc2 100644
--- a/cpukit/posix/src/psignalclearprocesssignals.c
+++ b/cpukit/posix/src/psignalclearprocesssignals.c
@@ -53,8 +53,6 @@ void _POSIX_signals_Clear_process_signals(
     }
     if ( clear_signal ) {
       _POSIX_signals_Pending &= ~mask;
-      if ( !_POSIX_signals_Pending )
-	_Thread_Do_post_task_switch_extension--;
     }
   _ISR_Enable( level );
 }
diff --git a/cpukit/posix/src/psignalsetprocesssignals.c b/cpukit/posix/src/psignalsetprocesssignals.c
index 25209f3c4d..cb4ad8b241 100644
--- a/cpukit/posix/src/psignalsetprocesssignals.c
+++ b/cpukit/posix/src/psignalsetprocesssignals.c
@@ -41,8 +41,6 @@ void _POSIX_signals_Set_process_signals(
   ISR_Level  level;
 
   _ISR_Disable( level );
-    if ( !_POSIX_signals_Pending )
-      _Thread_Do_post_task_switch_extension++;
     _POSIX_signals_Pending |= mask;
   _ISR_Enable( level );
 }
diff --git a/cpukit/posix/src/psignalunblockthread.c b/cpukit/posix/src/psignalunblockthread.c
index fdba79a00c..912ac34694 100644
--- a/cpukit/posix/src/psignalunblockthread.c
+++ b/cpukit/posix/src/psignalunblockthread.c
@@ -98,8 +98,6 @@ bool _POSIX_signals_Unblock_thread(
      *    + Any other combination, do nothing.
      */
 
-    the_thread->do_post_task_switch_extension = true;
-
     if ( the_thread->current_state & STATES_INTERRUPTIBLE_BY_SIGNAL ) {
       the_thread->Wait.return_code = EINTR;
       /*
@@ -120,7 +118,7 @@ bool _POSIX_signals_Unblock_thread(
 	  }
     } else if ( the_thread->current_state == STATES_READY ) {
       if ( _ISR_Is_in_progress() && _Thread_Is_executing( the_thread ) )
-	_ISR_Signals_to_thread_executing = true;
+	_Context_Switch_necessary = true;
     }
   }
   return false;
diff --git a/cpukit/posix/src/pthreadcreate.c b/cpukit/posix/src/pthreadcreate.c
index c5ca86d52e..d7f08a5527 100644
--- a/cpukit/posix/src/pthreadcreate.c
+++ b/cpukit/posix/src/pthreadcreate.c
@@ -191,14 +191,6 @@ int pthread_create(
   api->schedparam  = schedparam;
 
   /*
-   *  This insures we evaluate the process-wide signals pending when we
-   *  first run.
-   *
-   *  NOTE:  Since the thread starts with all unblocked, this is necessary.
-   */
-  the_thread->do_post_task_switch_extension = true;
-
-  /*
    *  POSIX threads are allocated and started in one operation.
    */
   status = _Thread_Start(
diff --git a/cpukit/posix/src/pthreadkill.c b/cpukit/posix/src/pthreadkill.c
index 9b6bd408e0..6d96067049 100644
--- a/cpukit/posix/src/pthreadkill.c
+++ b/cpukit/posix/src/pthreadkill.c
@@ -63,10 +63,8 @@ int pthread_kill(
 
         (void) _POSIX_signals_Unblock_thread( the_thread, sig, NULL );
 
-        the_thread->do_post_task_switch_extension = true;
-
         if ( _ISR_Is_in_progress() && _Thread_Is_executing( the_thread ) )
-          _ISR_Signals_to_thread_executing = true;
+	  _Context_Switch_necessary = true;
       }
       _Thread_Enable_dispatch();
       return 0;
diff --git a/cpukit/posix/src/pthreadsigmask.c b/cpukit/posix/src/pthreadsigmask.c
index 2fdc720282..c97e75a89e 100644
--- a/cpukit/posix/src/pthreadsigmask.c
+++ b/cpukit/posix/src/pthreadsigmask.c
@@ -65,7 +65,6 @@ int pthread_sigmask(
 
   if ( ~api->signals_blocked &
        (api->signals_pending | _POSIX_signals_Pending) ) {
-    _Thread_Executing->do_post_task_switch_extension = true;
     _Thread_Dispatch();
   }
 
diff --git a/cpukit/rtems/src/signalsend.c b/cpukit/rtems/src/signalsend.c
index 038317e55d..f51b168997 100644
--- a/cpukit/rtems/src/signalsend.c
+++ b/cpukit/rtems/src/signalsend.c
@@ -64,10 +64,8 @@ rtems_status_code rtems_signal_send(
         if ( asr->is_enabled ) {
           _ASR_Post_signals( signal_set, &asr->signals_posted );
 
-          the_thread->do_post_task_switch_extension = true;
-
           if ( _ISR_Is_in_progress() && _Thread_Is_executing( the_thread ) )
-            _ISR_Signals_to_thread_executing = true;
+            _Context_Switch_necessary = true;
         } else {
           _ASR_Post_signals( signal_set, &asr->signals_pending );
         }
diff --git a/cpukit/rtems/src/taskmode.c b/cpukit/rtems/src/taskmode.c
index 56f707c5e7..57872b11ce 100644
--- a/cpukit/rtems/src/taskmode.c
+++ b/cpukit/rtems/src/taskmode.c
@@ -117,7 +117,6 @@ rtems_status_code rtems_task_mode(
       _ASR_Swap_signals( asr );
       if ( _ASR_Are_signals_pending( asr ) ) {
         needs_asr_dispatching = true;
-        executing->do_post_task_switch_extension = true;
       }
     }
   }
diff --git a/cpukit/score/Makefile.am b/cpukit/score/Makefile.am
index 7dd430fc5a..acf9a77c6e 100644
--- a/cpukit/score/Makefile.am
+++ b/cpukit/score/Makefile.am
@@ -24,15 +24,15 @@ include_rtems_score_HEADERS = include/rtems/score/address.h \
     include/rtems/score/coremutex.h include/rtems/score/coresem.h \
     include/rtems/score/heap.h include/rtems/score/protectedheap.h \
     include/rtems/score/interr.h include/rtems/score/isr.h \
-    include/rtems/score/object.h include/rtems/score/priority.h \
-    include/rtems/score/stack.h include/rtems/score/states.h \
-    include/rtems/score/sysstate.h include/rtems/score/thread.h \
-    include/rtems/score/threadq.h include/rtems/score/threadsync.h \
-    include/rtems/score/timespec.h include/rtems/score/timestamp.h \
-    include/rtems/score/timestamp64.h include/rtems/score/tod.h \
-    include/rtems/score/tqdata.h include/rtems/score/userext.h \
-    include/rtems/score/watchdog.h include/rtems/score/wkspace.h \
-    include/rtems/score/cpuopts.h
+    include/rtems/score/object.h include/rtems/score/percpu.h \
+    include/rtems/score/priority.h include/rtems/score/stack.h \
+    include/rtems/score/states.h include/rtems/score/sysstate.h \
+    include/rtems/score/thread.h include/rtems/score/threadq.h \
+    include/rtems/score/threadsync.h include/rtems/score/timespec.h \
+    include/rtems/score/timestamp.h include/rtems/score/timestamp64.h \
+    include/rtems/score/tod.h include/rtems/score/tqdata.h \
+    include/rtems/score/userext.h include/rtems/score/watchdog.h \
+    include/rtems/score/wkspace.h include/rtems/score/cpuopts.h
 
 if HAS_PTHREADS
 include_rtems_score_HEADERS += include/rtems/score/corespinlock.h \
@@ -101,6 +101,9 @@ libscore_a_SOURCES += src/coremutex.c src/coremutexflush.c \
     src/coremutexseize.c src/coremutexsurrender.c \
     src/coremutexseizeintr.c
 
+## CORE_PERCPU_C_FILES
+libscore_a_SOURCES += src/percpu.c
+
 ## CORE_RWLOCK_C_FILES
 if HAS_PTHREADS
 libscore_a_SOURCES += src/corerwlock.c src/corerwlockobtainread.c \
diff --git a/cpukit/score/include/rtems/score/context.h b/cpukit/score/include/rtems/score/context.h
index 862cf48fcd..8c1a1021e0 100644
--- a/cpukit/score/include/rtems/score/context.h
+++ b/cpukit/score/include/rtems/score/context.h
@@ -23,6 +23,9 @@
  *
  *  This handler encapsulates functionality which abstracts thread context
  *  management in a portable manner.
+ *
+ *  The context switch needed variable is contained in the per cpu
+ *  data structure.
  */
 /**@{*/
 
@@ -41,16 +44,6 @@ extern "C" {
 #define CONTEXT_FP_SIZE CPU_CONTEXT_FP_SIZE
 
 /**
- *  @brief Is Context Switch Needed?
- *
- *  This variable is set to true when a reschedule operation
- *  has determined that the processor should be taken away from the
- *  currently executing thread and given to the heir thread.
- */
-
-SCORE_EXTERN volatile bool _Context_Switch_necessary;
-
-/**
  *  @brief Initialize Context Area
  *  This routine initializes @a _the_context such that the stack
  *  pointer, interrupt level, and entry point are correct for the
diff --git a/cpukit/score/include/rtems/score/isr.h b/cpukit/score/include/rtems/score/isr.h
index 66adbcb943..6f8096a2a9 100644
--- a/cpukit/score/include/rtems/score/isr.h
+++ b/cpukit/score/include/rtems/score/isr.h
@@ -21,11 +21,16 @@
 #ifndef _RTEMS_SCORE_ISR_H
 #define _RTEMS_SCORE_ISR_H
 
+#include <rtems/score/percpu.h>
+
 /**
  *  @defgroup ScoreISR ISR Handler
  *
  *  This handler encapsulates functionality which provides the foundation
  *  ISR services used in all of the APIs supported by RTEMS.
+ *
+ *  The ISR Nest level counter variable is maintained as part of the
+ *  per cpu data structure.
  */
 /**@{*/
 
@@ -75,18 +80,6 @@ typedef ISR_Handler ( *ISR_Handler_entry )(
  */
 #define ISR_INTERRUPT_MAXIMUM_VECTOR_NUMBER  CPU_INTERRUPT_MAXIMUM_VECTOR_NUMBER
 
-/**
- *  The following is true if signals have been sent to the currently
- *  executing thread by an ISR handler.
- */
-SCORE_EXTERN bool       _ISR_Signals_to_thread_executing;
-
-/**
- *  The following contains the interrupt service routine nest level.
- *  When this variable is zero, a thread is executing.
- */
-SCORE_EXTERN volatile uint32_t   _ISR_Nest_level;
-
 #if (CPU_SIMPLE_VECTORED_INTERRUPTS == TRUE)
 /**
  *  The following declares the Vector Table.  Application
diff --git a/cpukit/score/include/rtems/score/percpu.h b/cpukit/score/include/rtems/score/percpu.h
new file mode 100644
index 0000000000..09f82ad663
--- /dev/null
+++ b/cpukit/score/include/rtems/score/percpu.h
@@ -0,0 +1,166 @@
+/**
+ *  @file  rtems/score/percpu.h
+ *
+ *  This include file defines the per CPU information required
+ *  by RTEMS.
+ */
+
+/*
+ *  COPYRIGHT (c) 1989-2010.
+ *  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.
+ *
+ *  $Id$
+ */
+
+#ifndef _RTEMS_PERCPU_H
+#define _RTEMS_PERCPU_H
+
+#ifdef ASM
+  #include <rtems/asm.h>
+#endif
+
+/**
+ *  @defgroup PerCPU RTEMS Per CPU Information
+ *
+ *  This defines the per CPU state information required by RTEMS
+ *  and the BSP.  In an SMP configuration, there will be multiple
+ *  instances of this data structure -- one per CPU -- and the
+ *  current CPU number will be used as the index.
+ */
+
+/**@{*/
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#ifndef ASM
+
+/**
+ * This forward defines the Thread Control Block structure.
+ */
+typedef struct Thread_Control_struct Thread_Control;
+
+/**
+ *  @brief Per CPU Core Structure
+ *
+ *  This structure is used to hold per core state information.
+ */
+typedef struct {
+#if (CPU_ALLOCATE_INTERRUPT_STACK == TRUE) || \
+    (CPU_HAS_SOFTWARE_INTERRUPT_STACK == TRUE)
+  /**
+   * This contains a pointer to the lower range of the interrupt stack for
+   * this CPU.  This is the address allocated and freed.
+   */
+  void  *interrupt_stack_low;
+
+  /**
+   * This contains a pointer to the interrupt stack pointer for this CPU.
+   * It will be loaded at the beginning on an ISR.
+   */
+  void  *interrupt_stack_high;
+#endif
+
+  /**
+   *
+   *  This contains the current interrupt nesting level on this
+   *  CPU.
+   */
+  uint32_t isr_nest_level;
+
+  /** This is the thread executing on this CPU. */
+  Thread_Control *executing;
+
+  /** This is the heir thread for this this CPU. */
+  Thread_Control *heir;
+
+  /** This is the idle thread for this CPU. */
+  Thread_Control *idle;
+
+  /** This is set to true when this CPU needs to run the dispatcher. */
+  volatile bool dispatch_needed;
+
+} Per_CPU_Control;
+#endif
+
+#ifdef ASM
+
+#if (CPU_ALLOCATE_INTERRUPT_STACK == TRUE) || \
+    (CPU_HAS_SOFTWARE_INTERRUPT_STACK == TRUE)
+  /*
+   *  If this CPU target lets RTEMS allocates the interrupt stack, then
+   *  we need to have places in the per cpu table to hold them.
+   */
+  #define PER_CPU_INTERRUPT_STACK_LOW   0
+  #define PER_CPU_INTERRUPT_STACK_HIGH  (1 * SIZEOF_VOID_P)
+  #define PER_CPU_END_STACK             (2 * SIZEOF_VOID_P)
+#else
+  /*
+   *  Otherwise, there are no interrupt stack addresses in the per CPU table.
+   */
+  #define PER_CPU_END_STACK             0
+#endif
+
+/*
+ *  These are the offsets of the required elements in the per CPU table.
+ */
+#define PER_CPU_ISR_NEST_LEVEL   PER_CPU_END_STACK + 0
+#define PER_CPU_EXECUTING        PER_CPU_END_STACK + (1 * SIZEOF_VOID_P)
+#define PER_CPU_HEIR             PER_CPU_END_STACK + (2 * SIZEOF_VOID_P)
+#define PER_CPU_IDLE             PER_CPU_END_STACK + (3 * SIZEOF_VOID_P)
+#define PER_CPU_DISPATCH_NEEDED  PER_CPU_END_STACK + (4 * SIZEOF_VOID_P)
+#define ISR_NEST_LEVEL \
+    (SYM(_Per_CPU_Information) + PER_CPU_ISR_NEST_LEVEL)
+#define DISPATCH_NEEDED \
+    (SYM(_Per_CPU_Information) + PER_CPU_DISPATCH_NEEDED)
+
+/*
+ * Do not define these offsets if they are not in the table.
+ */
+#if (CPU_ALLOCATE_INTERRUPT_STACK == TRUE) || \
+    (CPU_HAS_SOFTWARE_INTERRUPT_STACK == TRUE)
+  #define INTERRUPT_STACK_LOW \
+      (SYM(_Per_CPU_Information) + PER_CPU_INTERRUPT_STACK_LOW)
+  #define INTERRUPT_STACK_HIGH \
+      (SYM(_Per_CPU_Information) + PER_CPU_INTERRUPT_STACK_HIGH)
+#endif
+
+#endif
+
+#ifndef ASM
+
+/**
+ *  @brief Set of Per CPU Core Information
+ *
+ *  This is an array of per CPU core information.
+ */
+extern Per_CPU_Control _Per_CPU_Information;
+
+/*
+ * On an SMP system, these macros dereference the CPU core number.
+ * But on a non-SMP system, these macros are simple references.
+ * Thus when built for non-SMP, there should be no performance penalty.
+ */
+#define _Thread_Heir              _Per_CPU_Information.heir
+#define _Thread_Executing         _Per_CPU_Information.executing
+#define _Thread_Idle              _Per_CPU_Information.idle
+#define _ISR_Nest_level           _Per_CPU_Information.isr_nest_level
+#define _CPU_Interrupt_stack_low  _Per_CPU_Information.interrupt_stack_low
+#define _CPU_Interrupt_stack_high _Per_CPU_Information.interrupt_stack_high
+#define _Context_Switch_necessary _Per_CPU_Information.dispatch_needed
+
+#endif  /* ASM */
+
+#ifdef __cplusplus
+}
+#endif
+
+/**@}*/
+
+#endif
+/* end of include file */
diff --git a/cpukit/score/include/rtems/score/thread.h b/cpukit/score/include/rtems/score/thread.h
index 1e05df8ed0..ca4b04fa22 100644
--- a/cpukit/score/include/rtems/score/thread.h
+++ b/cpukit/score/include/rtems/score/thread.h
@@ -24,6 +24,13 @@
  *
  *  This handler encapsulates functionality related to the management of
  *  threads.  This includes the creation, deletion, and scheduling of threads.
+ *
+ *  The following variables are maintained as part of the per cpu data
+ *  structure.
+ *
+ *  + Idle thread pointer
+ *  + Executing thread pointer
+ *  + Heir thread pointer
  */
 /**@{*/
 
@@ -55,6 +62,7 @@ extern "C" {
   typedef uint32_t Thread_CPU_usage_t;
 #endif
 
+#include <rtems/score/percpu.h>
 #include <rtems/score/context.h>
 #include <rtems/score/cpu.h>
 #if defined(RTEMS_MULTIPROCESSING)
@@ -147,10 +155,6 @@ typedef enum {
   #endif
 }  Thread_CPU_budget_algorithms;
 
-/** This type defines the Thread Control Block structure.
- */
-typedef struct Thread_Control_struct Thread_Control;
-
 /**  This defines thes the entry point for the thread specific timeslice
  *   budget management algorithm.
  */
@@ -363,10 +367,6 @@ struct Thread_Control_struct {
   /** This field is true if the thread is offered globally */
   bool                                  is_global;
 #endif
-  /** This field is is true if the post task context switch should be
-   *  executed for this thread at the next context switch.
-   */
-  bool                                  do_post_task_switch_extension;
   /** This field is true if the thread is preemptible. */
   bool                                  is_preemptible;
 #if __RTEMS_ADA__
@@ -427,12 +427,6 @@ SCORE_EXTERN void *rtems_ada_self;
 SCORE_EXTERN Objects_Information _Thread_Internal_information;
 
 /**
- *  The following define the thread control pointers used to access
- *  and manipulate the idle thread.
- */
-SCORE_EXTERN Thread_Control *_Thread_Idle;
-
-/**
  *  The following context area contains the context of the "thread"
  *  which invoked the start multitasking routine.  This context is
  *  restored as the last action of the stop multitasking routine.  Thus
@@ -449,12 +443,6 @@ SCORE_EXTERN Context_Control _Thread_BSP_context;
 SCORE_EXTERN volatile uint32_t   _Thread_Dispatch_disable_level;
 
 /**
- *  If this is non-zero, then the post-task switch extension
- *  is run regardless of the state of the per thread flag.
- */
-SCORE_EXTERN uint32_t   _Thread_Do_post_task_switch_extension;
-
-/**
  *  The following holds how many user extensions are in the system.  This
  *  is used to determine how many user extension data areas to allocate
  *  per thread.
@@ -473,20 +461,6 @@ SCORE_EXTERN uint32_t   _Thread_Ticks_per_timeslice;
 SCORE_EXTERN Chain_Control *_Thread_Ready_chain;
 
 /**
- *  The following points to the thread which is currently executing.
- *  This thread is implicitly manipulated by numerous directives.
- */
-SCORE_EXTERN Thread_Control *_Thread_Executing;
-
-/**
- *  The following points to the highest priority ready thread
- *  in the system.  Unless the current thread is not preemptibl,
- *  then this thread will be context switched to when the next
- *  dispatch occurs.
- */
-SCORE_EXTERN Thread_Control *_Thread_Heir;
-
-/**
  *  The following points to the thread whose floating point
  *  context is currently loaded.
  */
diff --git a/cpukit/score/include/rtems/system.h b/cpukit/score/include/rtems/system.h
index ad6e77f125..2bb55d7c8e 100644
--- a/cpukit/score/include/rtems/system.h
+++ b/cpukit/score/include/rtems/system.h
@@ -169,6 +169,7 @@ typedef void * proc_ptr;
 #include <stdint.h>
 #endif
 #include <rtems/score/cpu.h>        /* processor specific information */
+#include <rtems/score/percpu.h>
 
 #ifndef ASM
 /**
diff --git a/cpukit/score/preinstall.am b/cpukit/score/preinstall.am
index da6f308f63..617272b28a 100644
--- a/cpukit/score/preinstall.am
+++ b/cpukit/score/preinstall.am
@@ -99,6 +99,10 @@ $(PROJECT_INCLUDE)/rtems/score/object.h: include/rtems/score/object.h $(PROJECT_
 	$(INSTALL_DATA) $< $(PROJECT_INCLUDE)/rtems/score/object.h
 PREINSTALL_FILES += $(PROJECT_INCLUDE)/rtems/score/object.h
 
+$(PROJECT_INCLUDE)/rtems/score/percpu.h: include/rtems/score/percpu.h $(PROJECT_INCLUDE)/rtems/score/$(dirstamp)
+	$(INSTALL_DATA) $< $(PROJECT_INCLUDE)/rtems/score/percpu.h
+PREINSTALL_FILES += $(PROJECT_INCLUDE)/rtems/score/percpu.h
+
 $(PROJECT_INCLUDE)/rtems/score/priority.h: include/rtems/score/priority.h $(PROJECT_INCLUDE)/rtems/score/$(dirstamp)
 	$(INSTALL_DATA) $< $(PROJECT_INCLUDE)/rtems/score/priority.h
 PREINSTALL_FILES += $(PROJECT_INCLUDE)/rtems/score/priority.h
diff --git a/cpukit/score/src/isr.c b/cpukit/score/src/isr.c
index 0c6956fb19..4925ee9117 100644
--- a/cpukit/score/src/isr.c
+++ b/cpukit/score/src/isr.c
@@ -34,8 +34,6 @@
 
 void _ISR_Handler_initialization( void )
 {
-  _ISR_Signals_to_thread_executing = false;
-
   _ISR_Nest_level = 0;
 
 #if (CPU_SIMPLE_VECTORED_INTERRUPTS == TRUE)
@@ -64,6 +62,9 @@ void _ISR_Handler_initialization( void )
     Configuration.interrupt_stack_size
   );
 
+  _CPU_Interrupt_stack_high = (void *)
+    ((uintptr_t) _CPU_Interrupt_stack_high & ~CPU_STACK_ALIGNMENT);
+
   /* Interrupt stack might have to be aligned and/or setup
    * in a specific way.
    */
diff --git a/cpukit/score/src/isrthreaddispatch.c b/cpukit/score/src/isrthreaddispatch.c
index 229c1fa70e..d0b499b210 100644
--- a/cpukit/score/src/isrthreaddispatch.c
+++ b/cpukit/score/src/isrthreaddispatch.c
@@ -33,15 +33,6 @@ void _ISR_Thread_dispatch( void )
 {
   if ( _Context_Switch_necessary ) {
     _Thread_Dispatch();
-  } else if ( _ISR_Signals_to_thread_executing ) {
-    _ISR_Signals_to_thread_executing = false;
-    if (
-      _Thread_Do_post_task_switch_extension
-        || _Thread_Executing->do_post_task_switch_extension
-    ) {
-      _Thread_Executing->do_post_task_switch_extension = false;
-      _API_extensions_Run_postswitch();
-    }
   }
 }
 
diff --git a/cpukit/score/src/percpu.c b/cpukit/score/src/percpu.c
new file mode 100644
index 0000000000..4c719af6db
--- /dev/null
+++ b/cpukit/score/src/percpu.c
@@ -0,0 +1,29 @@
+/*
+ *  COPYRIGHT (c) 1989-2010.
+ *  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.
+ *
+ *  $Id$
+ */
+
+#if HAVE_CONFIG_H
+#include "config.h"
+#endif
+
+#include <rtems/system.h>
+#include <rtems/score/thread.h>
+#include <rtems/score/percpu.h>
+#include <rtems/score/wkspace.h>
+#include <rtems/score/wkspace.h>
+#include <rtems/config.h>
+#include <string.h>
+
+/*
+ * On single core systems, we can efficiently directly access a single
+ * statically allocated per cpu structure.  And the fields are initialized
+ * as individual elements just like it has always been done.
+ */
+Per_CPU_Control _Per_CPU_Information;
diff --git a/cpukit/score/src/thread.c b/cpukit/score/src/thread.c
index cc99bf668b..e96770acf1 100644
--- a/cpukit/score/src/thread.c
+++ b/cpukit/score/src/thread.c
@@ -76,8 +76,6 @@ void _Thread_Handler_initialization(void)
   _Thread_Allocated_fp      = NULL;
 #endif
 
-  _Thread_Do_post_task_switch_extension = 0;
-
   _Thread_Maximum_extensions = maximum_extensions;
 
   _Thread_Ticks_per_timeslice  = ticks_per_timeslice;
diff --git a/cpukit/score/src/threaddispatch.c b/cpukit/score/src/threaddispatch.c
index e0d0f5cdf7..3d7fe24947 100644
--- a/cpukit/score/src/threaddispatch.c
+++ b/cpukit/score/src/threaddispatch.c
@@ -94,12 +94,26 @@ void _Thread_Dispatch( void )
     _Thread_Dispatch_disable_level = 1;
     _Context_Switch_necessary = false;
     _Thread_Executing = heir;
+
+    /*
+     *  When the heir and executing are the same, then we are being
+     *  requested to do the post switch dispatching.  This is normally
+     *  done to dispatch signals.
+     */
+    if ( heir == executing )
+      goto post_switch;
+
+    /*
+     *  Since heir and executing are not the same, we need to do a real
+     *  context switch.
+     */
 #if __RTEMS_ADA__
     executing->rtems_ada_self = rtems_ada_self;
     rtems_ada_self = heir->rtems_ada_self;
 #endif
     if ( heir->budget_algorithm == THREAD_CPU_BUDGET_ALGORITHM_RESET_TIMESLICE )
       heir->cpu_time_budget = _Thread_Ticks_per_timeslice;
+
     _ISR_Enable( level );
 
     #ifndef __RTEMS_USE_TICKS_FOR_STATISTICS__
@@ -170,14 +184,10 @@ void _Thread_Dispatch( void )
     _ISR_Disable( level );
   }
 
+post_switch:
   _Thread_Dispatch_disable_level = 0;
 
   _ISR_Enable( level );
 
-  if ( _Thread_Do_post_task_switch_extension ||
-       executing->do_post_task_switch_extension ) {
-    executing->do_post_task_switch_extension = false;
-    _API_extensions_Run_postswitch();
-  }
-
+  _API_extensions_Run_postswitch();
 }
diff --git a/cpukit/score/src/threadloadenv.c b/cpukit/score/src/threadloadenv.c
index 6a30adbdde..164db0115a 100644
--- a/cpukit/score/src/threadloadenv.c
+++ b/cpukit/score/src/threadloadenv.c
@@ -58,8 +58,6 @@ void _Thread_Load_environment(
 #endif
     is_fp = false;
 
-
-  the_thread->do_post_task_switch_extension = false;
   the_thread->is_preemptible   = the_thread->Start.is_preemptible;
   the_thread->budget_algorithm = the_thread->Start.budget_algorithm;
   the_thread->budget_callout   = the_thread->Start.budget_callout;