2002-05-15 Chris Johns <ccj@acm.org>

	* include/rtems/score/thread.h, inline/rtems/score/thread.inl,
	src/threaddispatch.c, src/threadinitialize.c:
	Move the C library re-enterrant support directly into
	the thread dispatch code. RTEMS needs libc and so requiring
	libc to use a user extension with its overhead is not the best
	solution. This patch lowers the overhead to 2 pointer moves.

5 files changed, 63 insertions, 0 deletions

diff --git a/c/src/exec/score/ChangeLog b/c/src/exec/score/ChangeLog
index 1c5606a9fd..f38230f27a 100644
--- a/c/src/exec/score/ChangeLog
+++ b/c/src/exec/score/ChangeLog
@@ -1,3 +1,12 @@
+2002-05-15	Chris Johns <ccj@acm.org>
+
+	* include/rtems/score/thread.h, inline/rtems/score/thread.inl,
+	src/threaddispatch.c, src/threadinitialize.c: 
+	Move the C library re-enterrant support directly into
+	the thread dispatch code. RTEMS needs libc and so requiring
+	libc to use a user extension with its overhead is not the best
+	solution. This patch lowers the overhead to 2 pointer moves.
+
 2002-05-03	Ralf Corsepius <corsepiu@faw.uni-ulm.de>
 
 	* include/Makefile.am: Work-around to autoconf-2.53 adding PACKAGE_*
diff --git a/c/src/exec/score/include/rtems/score/thread.h b/c/src/exec/score/include/rtems/score/thread.h
index 07f5d2a504..18d4774a5d 100644
--- a/c/src/exec/score/include/rtems/score/thread.h
+++ b/c/src/exec/score/include/rtems/score/thread.h
@@ -220,6 +220,7 @@ struct Thread_Control_struct {
 #if ( CPU_HARDWARE_FP == TRUE ) || ( CPU_SOFTWARE_FP == TRUE )
   void                                 *fp_context;
 #endif
+  void                                 *libc_reent;
   void                                 *API_Extensions[ THREAD_API_LAST + 1 ];
   void                                **extensions;
   rtems_task_variable_t                *task_variables;
@@ -317,6 +318,15 @@ SCORE_EXTERN Thread_Control *_Thread_Allocated_fp;
 #endif
 
 /*
+ * The C library re-enter-rant global pointer. Some C library implementations
+ * such as newlib have a single global pointer that changed during a context
+ * switch. The pointer points to that global pointer. The Thread control block
+ * holds a pointer to the task specific data.
+ */
+
+SCORE_EXTERN void **_Thread_libc_reent;
+
+/*
  *  _Thread_Handler_initialization
  *
  *  DESCRIPTION:
diff --git a/c/src/exec/score/inline/rtems/score/thread.inl b/c/src/exec/score/inline/rtems/score/thread.inl
index 0c98830f76..560006c9e9 100644
--- a/c/src/exec/score/inline/rtems/score/thread.inl
+++ b/c/src/exec/score/inline/rtems/score/thread.inl
@@ -387,5 +387,35 @@ RTEMS_INLINE_ROUTINE void _Thread_Internal_free (
   _Objects_Free( &_Thread_Internal_information, &the_task->Object );
 }
 
+/*PAGE
+ *
+ *  _Thread_Get_libc_reent
+ *
+ *  DESCRIPTION:
+ *
+ *  This routine returns the C library re-enterant pointer.
+ */
+ 
+RTEMS_INLINE_ROUTINE void **_Thread_Get_libc_reent( void )
+{
+  return _Thread_libc_reent;
+}
+
+/*PAGE
+ *
+ *  _Thread_Set_libc_reent
+ *
+ *  DESCRIPTION:
+ *
+ *  This routine set the C library re-enterant pointer.
+ */
+ 
+RTEMS_INLINE_ROUTINE void _Thread_Set_libc_reent (
+  void **libc_reent
+)
+{
+  _Thread_libc_reent = libc_reent;
+}
+
 #endif
 /* end of include file */
diff --git a/c/src/exec/score/src/threaddispatch.c b/c/src/exec/score/src/threaddispatch.c
index 18953ae596..eedc8cc9ee 100644
--- a/c/src/exec/score/src/threaddispatch.c
+++ b/c/src/exec/score/src/threaddispatch.c
@@ -74,6 +74,14 @@ void _Thread_Dispatch( void )
 
     heir->ticks_executed++;
 
+    /*
+     * Switch libc's task specific data.
+     */
+    if ( _Thread_libc_reent ) {
+      executing->libc_reent = *_Thread_libc_reent;
+      *_Thread_libc_reent = heir->libc_reent;
+    }
+
     _User_extensions_Thread_switch( executing, heir );
 
     if ( heir->budget_algorithm == THREAD_CPU_BUDGET_ALGORITHM_RESET_TIMESLICE )
diff --git a/c/src/exec/score/src/threadinitialize.c b/c/src/exec/score/src/threadinitialize.c
index feb07836e3..e850e3fe1f 100644
--- a/c/src/exec/score/src/threadinitialize.c
+++ b/c/src/exec/score/src/threadinitialize.c
@@ -115,6 +115,12 @@ boolean _Thread_Initialize(
 #endif
 
   /*
+   * Clear the libc reent hook.
+   */
+  
+  the_thread->libc_reent = NULL;
+  
+  /*
    *  Allocate the extensions area for this thread
    */