2006-03-07 Joel Sherrill <joel@OARcorp.com>

	PR 866/rtems
	* include/rtems/system.h, include/rtems/score/isr.h,
	inline/rtems/score/thread.inl, macros/rtems/score/thread.inl: Added
	memory barriers to enter and exit of dispatching and interrupt
	critical sections so GCC will not optimize and reorder code out of a
	critical section.

5 files changed, 49 insertions, 8 deletions

diff --git a/cpukit/score/ChangeLog b/cpukit/score/ChangeLog
index aea807b6d0..a8de148d84 100644
--- a/cpukit/score/ChangeLog
+++ b/cpukit/score/ChangeLog
@@ -1,3 +1,12 @@
+2006-03-07	Joel Sherrill <joel@OARcorp.com>
+
+	PR 866/rtems
+	* include/rtems/system.h, include/rtems/score/isr.h,
+	inline/rtems/score/thread.inl, macros/rtems/score/thread.inl: Added
+	memory barriers to enter and exit of dispatching and interrupt
+	critical sections so GCC will not optimize and reorder code out of a
+	critical section.
+
 2005-09-01	Joel Sherrill <joel@OARcorp.com>
 
 	PR 820/rtems
diff --git a/cpukit/score/include/rtems/score/isr.h b/cpukit/score/include/rtems/score/isr.h
index 2e46117294..a097ccdae0 100644
--- a/cpukit/score/include/rtems/score/isr.h
+++ b/cpukit/score/include/rtems/score/isr.h
@@ -111,7 +111,10 @@ void _ISR_Handler_initialization ( void );
  */
 
 #define _ISR_Disable( _level ) \
-        _CPU_ISR_Disable( _level )
+  do { \
+    _CPU_ISR_Disable( _level ); \
+    RTEMS_COMPILER_MEMORY_BARRIER(); \
+  } while (0)
 
 /*
  *  _ISR_Enable
@@ -124,7 +127,10 @@ void _ISR_Handler_initialization ( void );
  */
 
 #define _ISR_Enable( _level ) \
-        _CPU_ISR_Enable( _level )
+  do { \
+    RTEMS_COMPILER_MEMORY_BARRIER(); \
+    _CPU_ISR_Enable( _level ); \
+  } while (0)
 
 /*
  *  _ISR_Flash
@@ -144,7 +150,11 @@ void _ISR_Handler_initialization ( void );
  */
 
 #define _ISR_Flash( _level ) \
-        _CPU_ISR_Flash( _level )
+  do { \
+    RTEMS_COMPILER_MEMORY_BARRIER(); \
+    _CPU_ISR_Flash( _level ); \
+    RTEMS_COMPILER_MEMORY_BARRIER(); \
+  } while (0)
 
 /*
  *  _ISR_Install_vector
diff --git a/cpukit/score/include/rtems/system.h b/cpukit/score/include/rtems/system.h
index 22895adb25..6f3f04ec29 100644
--- a/cpukit/score/include/rtems/system.h
+++ b/cpukit/score/include/rtems/system.h
@@ -102,6 +102,17 @@ extern "C" {
 #endif
 
 /*
+ *  The following macro is a compiler specific way to ensure that memory
+ *  writes are not reordered around certian points.  This specifically can
+ *  impact interrupt disable and thread dispatching critical sections.
+ */
+#ifdef __GNUC__
+  #define RTEMS_COMPILER_MEMORY_BARRIER() asm volatile("" ::: "memory")
+#else
+  #define RTEMS_COMPILER_MEMORY_BARRIER()
+#endif
+
+/*
  *  The following are used by the POSIX implementation to catch bad paths.
  */
 
diff --git a/cpukit/score/inline/rtems/score/thread.inl b/cpukit/score/inline/rtems/score/thread.inl
index 1154c061d2..5e7729e7c8 100644
--- a/cpukit/score/inline/rtems/score/thread.inl
+++ b/cpukit/score/inline/rtems/score/thread.inl
@@ -184,6 +184,7 @@ RTEMS_INLINE_ROUTINE void _Thread_Deallocate_fp( void )
 RTEMS_INLINE_ROUTINE void _Thread_Disable_dispatch( void )
 {
   _Thread_Dispatch_disable_level += 1;
+  RTEMS_COMPILER_MEMORY_BARRIER();
 }
 
 /*PAGE
@@ -201,6 +202,7 @@ RTEMS_INLINE_ROUTINE void _Thread_Disable_dispatch( void )
 #if ( CPU_INLINE_ENABLE_DISPATCH == TRUE )
 RTEMS_INLINE_ROUTINE void _Thread_Enable_dispatch()
 {
+  RTEMS_COMPILER_MEMORY_BARRIER();
   if ( (--_Thread_Dispatch_disable_level) == 0 )
     _Thread_Dispatch();
 }
@@ -223,6 +225,7 @@ void _Thread_Enable_dispatch( void );
 
 RTEMS_INLINE_ROUTINE void _Thread_Unnest_dispatch( void )
 {
+  RTEMS_COMPILER_MEMORY_BARRIER();
   _Thread_Dispatch_disable_level -= 1;
 }
 
diff --git a/cpukit/score/macros/rtems/score/thread.inl b/cpukit/score/macros/rtems/score/thread.inl
index 090552e845..1ae1310254 100644
--- a/cpukit/score/macros/rtems/score/thread.inl
+++ b/cpukit/score/macros/rtems/score/thread.inl
@@ -126,7 +126,10 @@
  */
 
 #define _Thread_Disable_dispatch() \
-  _Thread_Dispatch_disable_level += 1
+  do { \
+    _Thread_Dispatch_disable_level += 1; \
+    RTEMS_COMPILER_MEMORY_BARRIER(); \
+  } while (0)
 
 /*PAGE
  *
@@ -136,9 +139,11 @@
 
 #if ( CPU_INLINE_ENABLE_DISPATCH == TRUE )
 #define _Thread_Enable_dispatch()  \
-      { if ( (--_Thread_Dispatch_disable_level) == 0 ) \
-             _Thread_Dispatch();  \
-      }
+  do { \
+    RTEMS_COMPILER_MEMORY_BARRIER(); \
+    if ( (--_Thread_Dispatch_disable_level) == 0 ) \
+       _Thread_Dispatch(); \
+  } while (0)
 #endif
 
 #if ( CPU_INLINE_ENABLE_DISPATCH == FALSE )
@@ -152,7 +157,10 @@ void _Thread_Enable_dispatch( void );
  */
 
 #define _Thread_Unnest_dispatch()  \
-  _Thread_Dispatch_disable_level -= 1
+  do { \
+    RTEMS_COMPILER_MEMORY_BARRIER(); \
+    _Thread_Dispatch_disable_level -= 1; \
+  } while (0)
 
 /*PAGE
  *