From d507c0373168e6375b1e876d79730bff8020cb58 Mon Sep 17 00:00:00 2001
From: Joel Sherrill <joel.sherrill@oarcorp.com>
Date: Thu, 3 Apr 2014 12:55:43 -0500
Subject: Disable per task variables when SMP is enabled

Per task variables are inherently unsafe in SMP systems. This
patch disables them from the build and adds warnings in the
appropriate documentation and configuration sections.
---
 cpukit/rtems/src/tasks.c | 41 ++++++++++++++++++++++++++++-------------
 1 file changed, 28 insertions(+), 13 deletions(-)

(limited to 'cpukit/rtems/src/tasks.c')

diff --git a/cpukit/rtems/src/tasks.c b/cpukit/rtems/src/tasks.c
index 594695080a..209a43cb07 100644
--- a/cpukit/rtems/src/tasks.c
+++ b/cpukit/rtems/src/tasks.c
@@ -72,7 +72,9 @@ static bool _RTEMS_tasks_Create_extension(
   _Event_Initialize( &api->System_event );
   _ASR_Initialize( &api->Signal );
   _Thread_Action_initialize( &api->Signal_action, _Signal_Action_handler );
+#if !defined(RTEMS_SMP)
   created->task_variables = NULL;
+#endif
 
   if ( rtems_configuration_get_notepads_enabled() ) {
     for (i=0; i < RTEMS_NUMBER_NOTEPADS; i++)
@@ -124,19 +126,25 @@ static void _RTEMS_tasks_Terminate_extension(
   Thread_Control *executing
 )
 {
-  rtems_task_variable_t *tvp, *next;
 
   /*
    *  Free per task variable memory
+   *
+   *  Per Task Variables are only enabled in uniprocessor configurations
    */
-
-  tvp = executing->task_variables;
-  executing->task_variables = NULL;
-  while (tvp) {
-    next = (rtems_task_variable_t *)tvp->next;
-    _RTEMS_Tasks_Invoke_task_variable_dtor( executing, tvp );
-    tvp = next;
-  }
+  #if !defined(RTEMS_SMP)
+    do { 
+      rtems_task_variable_t *tvp, *next;
+
+      tvp = executing->task_variables;
+      executing->task_variables = NULL;
+      while (tvp) {
+	next = (rtems_task_variable_t *)tvp->next;
+	_RTEMS_Tasks_Invoke_task_variable_dtor( executing, tvp );
+	tvp = next;
+      }
+    } while (0);
+  #endif
 
   /*
    *  Run all the key destructors
@@ -144,12 +152,15 @@ static void _RTEMS_tasks_Terminate_extension(
   _POSIX_Keys_Run_destructors( executing );
 }
 
+#if !defined(RTEMS_SMP)
 /*
  *  _RTEMS_tasks_Switch_extension
  *
  *  This extension routine is invoked at each context switch.
+ *
+ *  @note Since this only needs to address per-task variables, it is
+ *        disabled entirely for SMP configurations.
  */
-
 static void _RTEMS_tasks_Switch_extension(
   Thread_Control *executing,
   Thread_Control *heir
@@ -158,7 +169,7 @@ static void _RTEMS_tasks_Switch_extension(
   rtems_task_variable_t *tvp;
 
   /*
-   *  Per Task Variables
+   *  Per Task Variables are only enabled in uniprocessor configurations
    */
 
   tvp = executing->task_variables;
@@ -175,6 +186,10 @@ static void _RTEMS_tasks_Switch_extension(
     tvp = (rtems_task_variable_t *)tvp->next;
   }
 }
+#define RTEMS_TASKS_SWITCH_EXTENSION _RTEMS_tasks_Switch_extension
+#else 
+#define RTEMS_TASKS_SWITCH_EXTENSION NULL
+#endif
 
 API_extensions_Control _RTEMS_tasks_API_extensions = {
   #if defined(FUNCTIONALITY_NOT_CURRENTLY_USED_BY_ANY_API)
@@ -185,12 +200,12 @@ API_extensions_Control _RTEMS_tasks_API_extensions = {
 
 User_extensions_Control _RTEMS_tasks_User_extensions = {
   { NULL, NULL },
-  { { NULL, NULL }, _RTEMS_tasks_Switch_extension },
+  { { NULL, NULL }, RTEMS_TASKS_SWITCH_EXTENSION },
   { _RTEMS_tasks_Create_extension,            /* create */
     _RTEMS_tasks_Start_extension,             /* start */
     _RTEMS_tasks_Start_extension,             /* restart */
     _RTEMS_tasks_Delete_extension,            /* delete */
-    _RTEMS_tasks_Switch_extension,            /* switch */
+    RTEMS_TASKS_SWITCH_EXTENSION,             /* switch */
     NULL,                                     /* begin */
     NULL,                                     /* exitted */
     NULL,                                     /* fatal */
-- 
cgit v1.2.3