Introduce the prvTaskExitError() function for all ARM_CMn ports.

Introduce the configTASK_RETURN_ADDRESS macro for the GCC ARM_CMn ports.
Improve time slippage penalty when entering tickless mode is abandoned.

FreeRTOS/Source/portable/GCC/ARM_CM0/port.c

@@ -86,6 +86,15 @@
 /* Constants required to set up the initial stack. */
 #define portINITIAL_XPSR			( 0x01000000 )
 
+/* Let the user override the pre-loading of the initial LR with the address of
+prvTaskExitError() in case is messes up unwinding of the stack in the
+debugger. */
+#ifdef configTASK_RETURN_ADDRESS
+	#define portTASK_RETURN_ADDRESS	configTASK_RETURN_ADDRESS
+#else
+	#define portTASK_RETURN_ADDRESS	prvTaskExitError
+#endif
+
 /* Each task maintains its own interrupt status in the critical nesting
 variable. */
 static unsigned portBASE_TYPE uxCriticalNesting = 0xaaaaaaaa;
@@ -126,7 +135,7 @@ portSTACK_TYPE *pxPortInitialiseStack( portSTACK_TYPE *pxTopOfStack, pdTASK_CODE
 	pxTopOfStack--;
 	*pxTopOfStack = ( portSTACK_TYPE ) pxCode;	/* PC */
 	pxTopOfStack--;
-	*pxTopOfStack = ( portSTACK_TYPE ) prvTaskExitError;	/* LR */
+	*pxTopOfStack = ( portSTACK_TYPE ) portTASK_RETURN_ADDRESS;	/* LR */
 	pxTopOfStack -= 5;	/* R12, R3, R2 and R1. */
 	*pxTopOfStack = ( portSTACK_TYPE ) pvParameters;	/* R0 */
 	pxTopOfStack -= 8; /* R11..R4. */

FreeRTOS/Source/portable/GCC/ARM_CM3/port.c

@@ -118,6 +118,15 @@ occurred while the SysTick counter is stopped during tickless idle
 calculations. */
 #define portMISSED_COUNTS_FACTOR			( 45UL )
 
+/* Let the user override the pre-loading of the initial LR with the address of
+prvTaskExitError() in case is messes up unwinding of the stack in the
+debugger. */
+#ifdef configTASK_RETURN_ADDRESS
+	#define portTASK_RETURN_ADDRESS	configTASK_RETURN_ADDRESS
+#else
+	#define portTASK_RETURN_ADDRESS	prvTaskExitError
+#endif
+
 /* Each task maintains its own interrupt status in the critical nesting
 variable. */
 static unsigned portBASE_TYPE uxCriticalNesting = 0xaaaaaaaa;
@@ -141,6 +150,11 @@ void vPortSVCHandler( void ) __attribute__ (( naked ));
  */
 static void prvPortStartFirstTask( void ) __attribute__ (( naked ));
 
+/*
+ * Used to catch tasks that attempt to return from their implementing function.
+ */
+static void prvTaskExitError( void );
+
 /*-----------------------------------------------------------*/
 
 /*
@@ -191,7 +205,7 @@ portSTACK_TYPE *pxPortInitialiseStack( portSTACK_TYPE *pxTopOfStack, pdTASK_CODE
 	pxTopOfStack--;
 	*pxTopOfStack = ( portSTACK_TYPE ) pxCode;	/* PC */
 	pxTopOfStack--;
-	*pxTopOfStack = 0;	/* LR */
+	*pxTopOfStack = ( portSTACK_TYPE ) portTASK_RETURN_ADDRESS;	/* LR */
 	pxTopOfStack -= 5;	/* R12, R3, R2 and R1. */
 	*pxTopOfStack = ( portSTACK_TYPE ) pvParameters;	/* R0 */
 	pxTopOfStack -= 8;	/* R11, R10, R9, R8, R7, R6, R5 and R4. */
@@ -200,6 +214,20 @@ portSTACK_TYPE *pxPortInitialiseStack( portSTACK_TYPE *pxTopOfStack, pdTASK_CODE
 }
 /*-----------------------------------------------------------*/
 
+static void prvTaskExitError( void )
+{
+	/* A function that implements a task must not exit or attempt to return to
+	its caller as there is nothing to return to.  If a task wants to exit it 
+	should instead call vTaskDelete( NULL ).
+	
+	Artificially force an assert() to be triggered if configASSERT() is 
+	defined, then stop here so application writers can catch the error. */
+	configASSERT( uxCriticalNesting == ~0UL );
+	portDISABLE_INTERRUPTS();	
+	for( ;; );
+}
+/*-----------------------------------------------------------*/
+
 void vPortSVCHandler( void )
 {
 	__asm volatile (
@@ -465,9 +493,17 @@ void xPortSysTickHandler( void )
 		to be unsuspended then abandon the low power entry. */
 		if( eTaskConfirmSleepModeStatus() == eAbortSleep )
 		{
+			/* Restart from whatever is left in the count register to complete
+			this tick period. */
+			portNVIC_SYSTICK_LOAD_REG = portNVIC_SYSTICK_CURRENT_VALUE_REG;
+			
 			/* Restart SysTick. */
 			portNVIC_SYSTICK_CTRL_REG = portNVIC_SYSTICK_CLK_BIT | portNVIC_SYSTICK_INT_BIT | portNVIC_SYSTICK_ENABLE_BIT;
 			
+			/* Reset the reload register to the value required for normal tick
+			periods. */
+			portNVIC_SYSTICK_LOAD_REG = ulTimerCountsForOneTick - 1UL;
+
 			/* Re-enable interrupts - see comments above the cpsid instruction()
 			above. */
 			__asm volatile( "cpsie i" );

FreeRTOS/Source/portable/GCC/ARM_CM4F/port.c

@@ -120,6 +120,15 @@ occurred while the SysTick counter is stopped during tickless idle
 calculations. */
 #define portMISSED_COUNTS_FACTOR			( 45UL )
 
+/* Let the user override the pre-loading of the initial LR with the address of
+prvTaskExitError() in case is messes up unwinding of the stack in the
+debugger. */
+#ifdef configTASK_RETURN_ADDRESS
+	#define portTASK_RETURN_ADDRESS	configTASK_RETURN_ADDRESS
+#else
+	#define portTASK_RETURN_ADDRESS	prvTaskExitError
+#endif
+
 /* Each task maintains its own interrupt status in the critical nesting
 variable. */
 static unsigned portBASE_TYPE uxCriticalNesting = 0xaaaaaaaa;
@@ -148,6 +157,11 @@ static void prvPortStartFirstTask( void ) __attribute__ (( naked ));
  */
  static void vPortEnableVFP( void ) __attribute__ (( naked ));
 
+/*
+ * Used to catch tasks that attempt to return from their implementing function.
+ */
+static void prvTaskExitError( void );
+
 /*-----------------------------------------------------------*/
 
 /*
@@ -202,7 +216,7 @@ portSTACK_TYPE *pxPortInitialiseStack( portSTACK_TYPE *pxTopOfStack, pdTASK_CODE
 	pxTopOfStack--;
 	*pxTopOfStack = ( portSTACK_TYPE ) pxCode;	/* PC */
 	pxTopOfStack--;
-	*pxTopOfStack = 0;	/* LR */
+	*pxTopOfStack = ( portSTACK_TYPE ) portTASK_RETURN_ADDRESS;	/* LR */
 
 	/* Save code space by skipping register initialisation. */
 	pxTopOfStack -= 5;	/* R12, R3, R2 and R1. */
@@ -219,6 +233,20 @@ portSTACK_TYPE *pxPortInitialiseStack( portSTACK_TYPE *pxTopOfStack, pdTASK_CODE
 }
 /*-----------------------------------------------------------*/
 
+static void prvTaskExitError( void )
+{
+	/* A function that implements a task must not exit or attempt to return to
+	its caller as there is nothing to return to.  If a task wants to exit it
+	should instead call vTaskDelete( NULL ).
+
+	Artificially force an assert() to be triggered if configASSERT() is
+	defined, then stop here so application writers can catch the error. */
+	configASSERT( uxCriticalNesting == ~0UL );
+	portDISABLE_INTERRUPTS();
+	for( ;; );
+}
+/*-----------------------------------------------------------*/
+
 void vPortSVCHandler( void )
 {
 	__asm volatile (
@@ -406,7 +434,7 @@ void xPortPendSVHandler( void )
 	(
 	"	mrs r0, psp							\n"
 	"										\n"
-	"	ldr	r3, pxCurrentTCBConst				\n" /* Get the location of the current TCB. */
+	"	ldr	r3, pxCurrentTCBConst			\n" /* Get the location of the current TCB. */
 	"	ldr	r2, [r3]						\n"
 	"										\n"
 	"	tst r14, #0x10						\n" /* Is the task using the FPU context?  If so, push high vfp registers. */
@@ -435,6 +463,14 @@ void xPortPendSVHandler( void )
 	"	vldmiaeq r0!, {s16-s31}				\n"
 	"										\n"
 	"	msr psp, r0							\n"
+	"										\n"
+	#ifdef WORKAROUND_PMU_CM001 /* XMC4000 specific errata workaround. */
+		#if WORKAROUND_PMU_CM001 == 1
+	"			push { r14 }				\n"
+	"			pop { pc }					\n"
+		#endif
+	#endif
+	"										\n"
 	"	bx r14								\n"
 	"										\n"
 	"	.align 2							\n"
@@ -500,9 +536,17 @@ void xPortSysTickHandler( void )
 		to be unsuspended then abandon the low power entry. */
 		if( eTaskConfirmSleepModeStatus() == eAbortSleep )
 		{
+			/* Restart from whatever is left in the count register to complete
+			this tick period. */
+			portNVIC_SYSTICK_LOAD_REG = portNVIC_SYSTICK_CURRENT_VALUE_REG;
+
 			/* Restart SysTick. */
 			portNVIC_SYSTICK_CTRL_REG = portNVIC_SYSTICK_CLK_BIT | portNVIC_SYSTICK_INT_BIT | portNVIC_SYSTICK_ENABLE_BIT;
 
+			/* Reset the reload register to the value required for normal tick
+			periods. */
+			portNVIC_SYSTICK_LOAD_REG = ulTimerCountsForOneTick - 1UL;
+
 			/* Re-enable interrupts - see comments above the cpsid instruction()
 			above. */
 			__asm volatile( "cpsie i" );

FreeRTOS/Source/portable/IAR/ARM_CM3/port.c

@@ -97,7 +97,7 @@
 #define portNVIC_PENDSV_PRI					( ( ( unsigned long ) configKERNEL_INTERRUPT_PRIORITY ) << 16UL )
 #define portNVIC_SYSTICK_PRI				( ( ( unsigned long ) configKERNEL_INTERRUPT_PRIORITY ) << 24UL )
 
-/* Constants required to check the validity of an interrupt prority. */
+/* Constants required to check the validity of an interrupt priority. */
 #define portFIRST_USER_INTERRUPT_NUMBER		( 16 )
 #define portNVIC_IP_REGISTERS_OFFSET_16 	( 0xE000E3F0 )
 #define portAIRCR_REG						( * ( ( volatile unsigned long * ) 0xE000ED0C ) )
@@ -146,6 +146,11 @@ void xPortSysTickHandler( void );
  */
 extern void vPortStartFirstTask( void );
 
+/*
+ * Used to catch tasks that attempt to return from their implementing function.
+ */
+static void prvTaskExitError( void );
+
 /*-----------------------------------------------------------*/
 
 /*
@@ -196,7 +201,7 @@ portSTACK_TYPE *pxPortInitialiseStack( portSTACK_TYPE *pxTopOfStack, pdTASK_CODE
 	pxTopOfStack--;
 	*pxTopOfStack = ( portSTACK_TYPE ) pxCode;	/* PC */
 	pxTopOfStack--;
-	*pxTopOfStack = 0;	/* LR */
+	*pxTopOfStack = ( portSTACK_TYPE ) prvTaskExitError;	/* LR */
 	pxTopOfStack -= 5;	/* R12, R3, R2 and R1. */
 	*pxTopOfStack = ( portSTACK_TYPE ) pvParameters;	/* R0 */
 	pxTopOfStack -= 8;	/* R11, R10, R9, R8, R7, R6, R5 and R4. */
@@ -205,6 +210,20 @@ portSTACK_TYPE *pxPortInitialiseStack( portSTACK_TYPE *pxTopOfStack, pdTASK_CODE
 }
 /*-----------------------------------------------------------*/
 
+static void prvTaskExitError( void )
+{
+	/* A function that implements a task must not exit or attempt to return to
+	its caller as there is nothing to return to.  If a task wants to exit it 
+	should instead call vTaskDelete( NULL ).
+	
+	Artificially force an assert() to be triggered if configASSERT() is 
+	defined, then stop here so application writers can catch the error. */
+	configASSERT( uxCriticalNesting == ~0UL );
+	portDISABLE_INTERRUPTS();	
+	for( ;; );
+}
+/*-----------------------------------------------------------*/
+
 /*
  * See header file for description.
  */
@@ -367,9 +386,17 @@ void xPortSysTickHandler( void )
 		to be unsuspended then abandon the low power entry. */
 		if( eTaskConfirmSleepModeStatus() == eAbortSleep )
 		{
+			/* Restart from whatever is left in the count register to complete
+			this tick period. */
+			portNVIC_SYSTICK_LOAD_REG = portNVIC_SYSTICK_CURRENT_VALUE_REG;
+			
 			/* Restart SysTick. */
 			portNVIC_SYSTICK_CTRL_REG = portNVIC_SYSTICK_CLK_BIT | portNVIC_SYSTICK_INT_BIT | portNVIC_SYSTICK_ENABLE_BIT;
 			
+			/* Reset the reload register to the value required for normal tick
+			periods. */
+			portNVIC_SYSTICK_LOAD_REG = ulTimerCountsForOneTick - 1UL;
+
 			/* Re-enable interrupts - see comments above __disable_interrupt()
 			call above. */
 			__enable_interrupt();

FreeRTOS/Source/portable/IAR/ARM_CM4F/portasm.s

@@ -120,6 +120,14 @@ xPortPendSVHandler:
 	vldmiaeq r0!, {s16-s31}
 
 	msr psp, r0
+
+	#ifdef WORKAROUND_PMU_CM001 /* XMC4000 specific errata */
+		#if WORKAROUND_PMU_CM001 == 1
+			push { r14 }
+			pop { pc }
+		#endif
+	#endif
+
 	bx r14
 
 

FreeRTOS/Source/portable/RVDS/ARM_CM3/port.c

@@ -154,6 +154,11 @@ void vPortSVCHandler( void );
  */
 static void prvStartFirstTask( void );
 
+/*
+ * Used to catch tasks that attempt to return from their implementing function.
+ */
+static void prvTaskExitError( void );
+
 /*-----------------------------------------------------------*/
 
 /*
@@ -204,7 +209,8 @@ portSTACK_TYPE *pxPortInitialiseStack( portSTACK_TYPE *pxTopOfStack, pdTASK_CODE
 	pxTopOfStack--;
 	*pxTopOfStack = ( portSTACK_TYPE ) pxCode;	/* PC */
 	pxTopOfStack--;
-	*pxTopOfStack = 0;	/* LR */
+	*pxTopOfStack = ( portSTACK_TYPE ) prvTaskExitError;	/* LR */
+
 	pxTopOfStack -= 5;	/* R12, R3, R2 and R1. */
 	*pxTopOfStack = ( portSTACK_TYPE ) pvParameters;	/* R0 */
 	pxTopOfStack -= 8;	/* R11, R10, R9, R8, R7, R6, R5 and R4. */
@@ -213,6 +219,20 @@ portSTACK_TYPE *pxPortInitialiseStack( portSTACK_TYPE *pxTopOfStack, pdTASK_CODE
 }
 /*-----------------------------------------------------------*/
 
+static void prvTaskExitError( void )
+{
+	/* A function that implements a task must not exit or attempt to return to
+	its caller as there is nothing to return to.  If a task wants to exit it 
+	should instead call vTaskDelete( NULL ).
+	
+	Artificially force an assert() to be triggered if configASSERT() is 
+	defined, then stop here so application writers can catch the error. */
+	configASSERT( uxCriticalNesting == ~0UL );
+	portDISABLE_INTERRUPTS();	
+	for( ;; );
+}
+/*-----------------------------------------------------------*/
+
 __asm void vPortSVCHandler( void )
 {
 	PRESERVE8
@@ -442,9 +462,17 @@ void xPortSysTickHandler( void )
 		to be unsuspended then abandon the low power entry. */
 		if( eTaskConfirmSleepModeStatus() == eAbortSleep )
 		{
+			/* Restart from whatever is left in the count register to complete
+			this tick period. */
+			portNVIC_SYSTICK_LOAD_REG = portNVIC_SYSTICK_CURRENT_VALUE_REG;
+			
 			/* Restart SysTick. */
 			portNVIC_SYSTICK_CTRL_REG = portNVIC_SYSTICK_CLK_BIT | portNVIC_SYSTICK_INT_BIT | portNVIC_SYSTICK_ENABLE_BIT;
 			
+			/* Reset the reload register to the value required for normal tick
+			periods. */
+			portNVIC_SYSTICK_LOAD_REG = ulTimerCountsForOneTick - 1UL;
+
 			/* Re-enable interrupts - see comments above __disable_irq() call
 			above. */
 			__enable_irq();

FreeRTOS/Source/portable/RVDS/ARM_CM4F/port.c

@@ -163,6 +163,12 @@ static void prvStartFirstTask( void );
  * Functions defined in portasm.s to enable the VFP.
  */
 static void prvEnableVFP( void );
+
+/*
+ * Used to catch tasks that attempt to return from their implementing function.
+ */
+static void prvTaskExitError( void );
+
 /*-----------------------------------------------------------*/
 
 /*
@@ -217,7 +223,7 @@ portSTACK_TYPE *pxPortInitialiseStack( portSTACK_TYPE *pxTopOfStack, pdTASK_CODE
 	pxTopOfStack--;
 	*pxTopOfStack = ( portSTACK_TYPE ) pxCode;	/* PC */
 	pxTopOfStack--;
-	*pxTopOfStack = 0;	/* LR */
+	*pxTopOfStack = ( portSTACK_TYPE ) prvTaskExitError;	/* LR */
 
 	/* Save code space by skipping register initialisation. */
 	pxTopOfStack -= 5;	/* R12, R3, R2 and R1. */
@@ -234,6 +240,20 @@ portSTACK_TYPE *pxPortInitialiseStack( portSTACK_TYPE *pxTopOfStack, pdTASK_CODE
 }
 /*-----------------------------------------------------------*/
 
+static void prvTaskExitError( void )
+{
+	/* A function that implements a task must not exit or attempt to return to
+	its caller as there is nothing to return to.  If a task wants to exit it 
+	should instead call vTaskDelete( NULL ).
+	
+	Artificially force an assert() to be triggered if configASSERT() is 
+	defined, then stop here so application writers can catch the error. */
+	configASSERT( uxCriticalNesting == ~0UL );
+	portDISABLE_INTERRUPTS();	
+	for( ;; );
+}
+/*-----------------------------------------------------------*/
+
 __asm void vPortSVCHandler( void )
 {
 	PRESERVE8
@@ -444,6 +464,14 @@ __asm void xPortPendSVHandler( void )
 	vldmiaeq r0!, {s16-s31}
 
 	msr psp, r0
+	
+	#ifdef WORKAROUND_PMU_CM001 /* XMC4000 specific errata */
+		#if WORKAROUND_PMU_CM001 == 1
+			push { r14 }
+			pop { pc }
+		#endif
+	#endif
+	
 	bx r14
 	nop
 }
@@ -505,9 +533,17 @@ void xPortSysTickHandler( void )
 		to be unsuspended then abandon the low power entry. */
 		if( eTaskConfirmSleepModeStatus() == eAbortSleep )
 		{
+			/* Restart from whatever is left in the count register to complete
+			this tick period. */
+			portNVIC_SYSTICK_LOAD_REG = portNVIC_SYSTICK_CURRENT_VALUE_REG;
+			
 			/* Restart SysTick. */
 			portNVIC_SYSTICK_CTRL_REG = portNVIC_SYSTICK_CLK_BIT | portNVIC_SYSTICK_INT_BIT | portNVIC_SYSTICK_ENABLE_BIT;
 			
+			/* Reset the reload register to the value required for normal tick
+			periods. */
+			portNVIC_SYSTICK_LOAD_REG = ulTimerCountsForOneTick - 1UL;
+
 			/* Re-enable interrupts - see comments above __disable_irq() call
 			above. */
 			__enable_irq();