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/Makefile.am

@@ -106,10 +106,13 @@ librtems_a_SOURCES += src/taskstart.c
 librtems_a_SOURCES += src/tasksuspend.c
 librtems_a_SOURCES += src/taskwakeafter.c
 librtems_a_SOURCES += src/taskwakewhen.c
+if HAS_SMP
+else
 librtems_a_SOURCES += src/taskvariableadd.c
 librtems_a_SOURCES += src/taskvariabledelete.c
 librtems_a_SOURCES += src/taskvariableget.c
 librtems_a_SOURCES += src/taskvariable_invoke_dtor.c
+endif
 librtems_a_SOURCES += src/taskdata.c
 
 ## RATEMON_C_FILES

cpukit/rtems/include/rtems/rtems/tasks.h

@@ -28,7 +28,7 @@
  */
 
 /*
- * COPYRIGHT (c) 1989-2011.
+ * COPYRIGHT (c) 1989-2014.
  * On-Line Applications Research Corporation (OAR).
  *
  * The license and distribution terms for this file may be
@@ -449,17 +449,18 @@ rtems_status_code rtems_task_wake_after(
  *
  *  This directive returns a status indicating whether or not
  *  the specified task is suspended.
- *
- *  RTEMS Task Manager
  */
 rtems_status_code rtems_task_is_suspended(
   rtems_id   id
 );
 
+#if !defined(RTEMS_SMP)
 /**
  *  @brief RTEMS Add Task Variable
  *
  *  This directive adds a per task variable.
+ *
+ *  @note This service is not available in SMP configurations.
  */
 rtems_status_code rtems_task_variable_add(
   rtems_id  tid,
@@ -470,9 +471,9 @@ rtems_status_code rtems_task_variable_add(
 /**
  *  @brief Get a per-task variable
  *
- *  RTEMS Task Variable Get
- *
  *  This directive gets the value of a task variable.
+ *
+ *  @note This service is not available in SMP configurations.
  */
 rtems_status_code rtems_task_variable_get(
   rtems_id tid,
@@ -484,11 +485,14 @@ rtems_status_code rtems_task_variable_get(
  *  @brief RTEMS Delete Task Variable
  *
  *  This directive removes a per task variable.
+ *
+ *  @note This service is not available in SMP configurations.
  */
 rtems_status_code rtems_task_variable_delete(
   rtems_id  tid,
   void    **ptr
 );
+#endif
 
 #if defined(__RTEMS_HAVE_SYS_CPUSET_H__) && defined(RTEMS_SMP)
 /**

cpukit/rtems/include/rtems/rtems/tasksimpl.h

@@ -6,7 +6,7 @@
  * @brief Classic Tasks Manager Implementation
  */
 
-/*  COPYRIGHT (c) 1989-2008.
+/*  COPYRIGHT (c) 1989-2014.
  *  On-Line Applications Research Corporation (OAR).
  *
  *  The license and distribution terms for this file may be
@@ -66,6 +66,7 @@ void _RTEMS_tasks_Manager_initialization(void);
  */
 void _RTEMS_tasks_Initialize_user_tasks( void );
 
+#if !defined(RTEMS_SMP)
 /**
  *  @brief RTEMS Tasks Invoke Task Variable Destructor
  *
@@ -76,6 +77,7 @@ void _RTEMS_Tasks_Invoke_task_variable_dtor(
   Thread_Control        *the_thread,
   rtems_task_variable_t *tvp
 );
+#endif
 
 RTEMS_INLINE_ROUTINE Thread_Control *_RTEMS_tasks_Allocate(void)
 {

cpukit/rtems/mainpage.h

@@ -5,7 +5,7 @@
  */
 
 /*
- *  COPYRIGHT (c) 1989-2011.
+ *  COPYRIGHT (c) 1989-2014.
  *  On-Line Applications Research Corporation (OAR).
  *
  *  The license and distribution terms for this file may be
@@ -887,6 +887,10 @@
  * A critical point with per-task variables is that each task must separately
  * request that the same global variable is per-task private.
  *
+ * @b{WARNING}: Per-task variables are fundamentally incorrect in SMP
+ *              systems and should not be used in SMP applications. They
+ *              are disabled.
+ *
  * @section ClassicTasksSecBuildingTaskAttributeSet Building a Task Attribute Set
  *
  * In general, an attribute set is built by a bitwise OR of the desired

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
    */
+  #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;
-  }
+      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 */

cpukit/rtems/src/taskvariable_invoke_dtor.c

@@ -6,7 +6,7 @@
  */
 
 /*
- *  COPYRIGHT (c) 1989-2007.
+ *  COPYRIGHT (c) 1989-2014.
  *  On-Line Applications Research Corporation (OAR).
  *
  *  The license and distribution terms for this file may be
@@ -18,6 +18,7 @@
 #include "config.h"
 #endif
 
+#if !defined(RTEMS_SMP)
 #include <rtems/rtems/tasksimpl.h>
 #include <rtems/score/threadimpl.h>
 #include <rtems/score/wkspace.h>
@@ -43,3 +44,4 @@ void _RTEMS_Tasks_Invoke_task_variable_dtor(
 
   _Workspace_Free(tvp);
 }
+#endif

cpukit/rtems/src/taskvariableadd.c

@@ -6,7 +6,7 @@
  */
 
 /*
- *  COPYRIGHT (c) 1989-2007.
+ *  COPYRIGHT (c) 1989-2014.
  *  On-Line Applications Research Corporation (OAR).
  *
  *  The license and distribution terms for this file may be
@@ -18,6 +18,7 @@
 #include "config.h"
 #endif
 
+#if !defined(RTEMS_SMP)
 #include <rtems/rtems/tasks.h>
 #include <rtems/score/threadimpl.h>
 #include <rtems/score/wkspace.h>
@@ -88,3 +89,4 @@ rtems_status_code rtems_task_variable_add(
   }
   return RTEMS_INVALID_ID;
 }
+#endif

cpukit/rtems/src/taskvariabledelete.c

@@ -6,7 +6,7 @@
  */
 
 /*
- *  COPYRIGHT (c) 1989-2007.
+ *  COPYRIGHT (c) 1989-2014.
  *  On-Line Applications Research Corporation (OAR).
  *
  *  The license and distribution terms for this file may be
@@ -18,6 +18,7 @@
 #include "config.h"
 #endif
 
+#if !defined(RTEMS_SMP)
 #include <rtems/rtems/tasksimpl.h>
 #include <rtems/score/threadimpl.h>
 #include <rtems/score/wkspace.h>
@@ -77,3 +78,4 @@ rtems_status_code rtems_task_variable_delete(
 
   return RTEMS_INVALID_ID;
 }
+#endif

cpukit/rtems/src/taskvariableget.c

@@ -6,7 +6,7 @@
  */
 
 /*
- *  COPYRIGHT (c) 1989-2007.
+ *  COPYRIGHT (c) 1989-2014.
  *  On-Line Applications Research Corporation (OAR).
  *
  *  The license and distribution terms for this file may be
@@ -18,6 +18,7 @@
 #include "config.h"
 #endif
 
+#if !defined(RTEMS_SMP)
 #include <rtems/rtems/tasksimpl.h>
 #include <rtems/score/threadimpl.h>
 #include <rtems/score/wkspace.h>
@@ -85,3 +86,4 @@ rtems_status_code rtems_task_variable_get(
   }
   return RTEMS_INVALID_ID;
 }
+#endif

cpukit/sapi/include/confdefs.h

@@ -1591,12 +1591,21 @@ const rtems_libio_helper rtems_fs_init_helper =
         (RTEMS_NUMBER_NOTEPADS * sizeof(uint32_t)))
   #endif
 
-  /**
-   * This macro calculates the memory required for task variables.
-   *
-   * NOTE: Each task variable is individually allocated from the Workspace.
-   *       Hence, we do the multiplication on the configured size.
-   */
+/**
+ * This macro calculates the memory required for task variables.
+ *
+ * Each task variable is individually allocated from the Workspace.
+ * Hence, we do the multiplication on the configured size.
+ *
+ * @note Per-task variables are disabled for SMP configurations.
+ */
+#if defined(RTEMS_SMP)
+  #ifdef CONFIGURE_MAXIMUM_TASK_VARIABLES
+    #error "Per-Task Variables are not safe for SMP systems and disabled"
+  #endif
+  #define CONFIGURE_MAXIMUM_TASK_VARIABLES                     0
+  #define CONFIGURE_MEMORY_FOR_TASK_VARIABLES(_task_variables) 0
+#else
   #ifndef CONFIGURE_MAXIMUM_TASK_VARIABLES
     #define CONFIGURE_MAXIMUM_TASK_VARIABLES                     0
     #define CONFIGURE_MEMORY_FOR_TASK_VARIABLES(_task_variables) 0
@@ -1605,6 +1614,7 @@ const rtems_libio_helper rtems_fs_init_helper =
       (_task_variables) * \
          _Configure_From_workspace(sizeof(rtems_task_variable_t))
   #endif
+#endif
 
   #ifndef CONFIGURE_MAXIMUM_TIMERS
     #define CONFIGURE_MAXIMUM_TIMERS             0

cpukit/score/include/rtems/score/thread.h

@@ -171,6 +171,7 @@ typedef enum {
  */
 typedef void (*Thread_CPU_budget_algorithm_callout )( Thread_Control * );
 
+#if !defined(RTEMS_SMP)
 /**
  *  @brief Forward reference to the per task variable structure..
  *
@@ -197,6 +198,7 @@ typedef struct {
   /** This field points to the destructor for this per task variable. */
   void                          (*dtor)(void *);
 } rtems_task_variable_t;
+#endif
 
 /**
  *  The following structure contains the information which defines
@@ -567,8 +569,10 @@ struct Thread_Control_struct {
   /** This field points to the user extension pointers. */
   void                                **extensions;
 
+#if !defined(RTEMS_SMP)
   /** This field points to the set of per task variables. */
   rtems_task_variable_t                *task_variables;
+#endif
 
   /**
    * This is the thread key value chain's control, which is used

doc/user/task.t

@@ -1,5 +1,5 @@
 @c
-@c  COPYRIGHT (c) 1988-2008.
+@c  COPYRIGHT (c) 1988-2014.
 @c  On-Line Applications Research Corporation (OAR).
 @c  All rights reserved.
 
@@ -340,6 +340,13 @@ containing the task's private "global" data.
 A critical point with per-task variables is that each task must separately
 request that the same global variable is per-task private.
 
+@b{WARNING}: Per-Task variables are inherently broken on SMP systems. They
+only work correctly when there is one task executing in the system and
+that task is the logical owner of the value in the per-task variable's
+location. There is no way for a single memory image to contain the
+correct value for each task executing on each core. Consequently,
+per-task variables are disabled in SMP configurations of RTEMS.
+
 @subsection Building a Task Attribute Set
 
 @cindex task attributes, building
@@ -1779,6 +1786,9 @@ is to have a single task variable that is a pointer to a dynamically
 allocated structure containing the task's private `global' data.
 In this case the destructor function could be `free'.
 
+Per-task variables are disabled in SMP configurations and this service
+is not available.
+
 @page
 
 @subsection TASK_VARIABLE_GET - Obtain value of a per task variable
@@ -1832,6 +1842,9 @@ will optimize it correctly.  In this case both the pointer
 @code{task_variable_value} and data referenced by @code{task_variable_value}
 should be considered volatile.
 
+Per-task variables are disabled in SMP configurations and this service
+is not available.
+
 @page
 
 @subsection TASK_VARIABLE_DELETE - Remove per task variable
@@ -1874,4 +1887,6 @@ This directive removes the given location from a task's context.
 
 @subheading NOTES:
 
-NONE
+Per-task variables are disabled in SMP configurations and this service
+is not available.
+

testsuites/psxtests/psxconfig01/init.c

@@ -7,6 +7,7 @@
  */
 
 /*
+ * Copyright (c) 2014. On-Line Applications Research Corporation (OAR).
  * Copyright (c) 2011-2012 embedded brains GmbH.  All rights reserved.
  *
  *  embedded brains GmbH
@@ -51,7 +52,9 @@ const char rtems_test_name[] = "PSXCONFIG 1";
 #define CONFIGURE_MAXIMUM_REGIONS 43
 #define CONFIGURE_MAXIMUM_SEMAPHORES 47
 #define CONFIGURE_MAXIMUM_TASKS 11
-#define CONFIGURE_MAXIMUM_TASK_VARIABLES 13
+#if !defined(RTEMS_SMP)
+  #define CONFIGURE_MAXIMUM_TASK_VARIABLES 13
+#endif
 #define CONFIGURE_MAXIMUM_TIMERS 59
 #define CONFIGURE_MAXIMUM_USER_EXTENSIONS 17
 
@@ -196,7 +199,9 @@ typedef struct {
 
 static char posix_name [NAME_MAX];
 
-static void *task_var;
+#if !defined(RTEMS_SMP)
+  static void *task_var;
+#endif
 
 static char *get_posix_name(char a, char b, char c, int i)
 {
@@ -208,10 +213,12 @@ static char *get_posix_name(char a, char b, char c, int i)
   return posix_name;
 }
 
+#if !defined(RTEMS_SMP)
 static void task_var_dtor(void *var __attribute__((unused)))
 {
   /* Do nothing */
 }
+#endif
 
 static void *posix_thread(void *arg __attribute__((unused)))
 {
@@ -403,12 +410,14 @@ static rtems_task Init(rtems_task_argument argument)
   );
 #endif
 
+#if !defined(RTEMS_SMP)
 #ifdef CONFIGURE_MAXIMUM_TASK_VARIABLES
   for (i = 0; i < CONFIGURE_MAXIMUM_TASK_VARIABLES; ++i) {
     sc = rtems_task_variable_add(RTEMS_SELF, &task_var, task_var_dtor);
     directive_failed(sc, "rtems_task_variable_add");
   }
 #endif
+#endif
 
 #ifdef CONFIGURE_MAXIMUM_TIMERS
   for (i = 0; i < CONFIGURE_MAXIMUM_TIMERS; ++i) {

testsuites/smptests/smpunsupported01/init.c

@@ -1,4 +1,5 @@
 /*
+ * Copyright (c) 2014 On-Line Applications Research Corporation (OAR).
  * Copyright (c) 2013-2014 embedded brains GmbH.  All rights reserved.
  *
  *  embedded brains GmbH
@@ -28,15 +29,6 @@ static void test(void)
 
   rtems_test_assert(rtems_configuration_is_smp_enabled());
 
-  sc = rtems_task_variable_add(RTEMS_SELF, NULL, NULL);
-  rtems_test_assert(sc == RTEMS_NOT_IMPLEMENTED);
-
-  sc = rtems_task_variable_delete(RTEMS_SELF, NULL);
-  rtems_test_assert(sc == RTEMS_NOT_IMPLEMENTED);
-
-  sc = rtems_task_variable_get(RTEMS_SELF, NULL, NULL);
-  rtems_test_assert(sc == RTEMS_NOT_IMPLEMENTED);
-
   sc = rtems_task_mode(RTEMS_NO_PREEMPT, RTEMS_PREEMPT_MASK, &mode);
   rtems_test_assert(sc == RTEMS_NOT_IMPLEMENTED);
 

testsuites/sptests/Makefile.am

@@ -5,7 +5,7 @@ ACLOCAL_AMFLAGS = -I ../aclocal
 SUBDIRS = \
          sp01 sp02 sp03 sp04 sp05 sp06 sp07 sp08 \
     sp10 sp11 sp12 sp13 sp14 sp15 sp16 sp17 sp18 sp19 \
-    sp20 sp21 sp22 sp23 sp24 sp25 sp26 sp27 sp27a sp28 sp29 \
+    sp20 sp21 sp22 sp23 sp24 sp25 sp26 sp27 sp27a           \
     sp30 sp31 sp32 sp33 sp34 sp35      sp37 sp38 sp39 \
     sp40 sp41 sp42 sp43 sp44 sp45 sp46 sp47 sp48 sp49 \
     sp50 sp51 sp52 sp53 sp54 sp55 sp56 sp57 sp58 sp59 \
@@ -33,6 +33,11 @@ SUBDIRS = \
     spsignal_err01 spport_err01 spmsgq_err01 spmsgq_err02 spsem_err01 \
     spsem_err02 sptask_err01 spevent_err03 sptask_err03 sptask_err02 \
     sptask_err04 spclock_err01 
+if HAS_SMP
+else
+SUBDIRS += sp29
+endif
+ SUBDIRS += spprofiling01
 SUBDIRS += spfatal28
 SUBDIRS += spthreadlife01
 SUBDIRS += spprofiling01

testsuites/sptests/configure.ac

@@ -34,6 +34,10 @@ AC_CHECK_SIZEOF([time_t])
 AC_CHECK_HEADERS([sys/cpuset.h])
 AM_CONDITIONAL(HAS_CPUSET,test x"${ac_cv_header_sys_cpuset_h}" = x"yes")
 
+# Some tests should not be built/run in SMP configurations
+RTEMS_CHECK_CPUOPTS([RTEMS_SMP])
+AM_CONDITIONAL(HAS_SMP,test "$rtems_cv_RTEMS_SMP" = "yes")
+
 # Explicitly list all Makefiles here
 AC_CONFIG_FILES([Makefile
 spfatal28/Makefile