Better consistency checking in xPortSysTickHandler

* For Cortex-M ports it's crucial that the SysTick has the lowest
(logical) priority otherwise very strange things will happen when the
SysTick interrupts a critical section. Therefor a consistency check has
been added to the xPortSysTickHandler to make sure that a critical
section was not interrupted.

* Added comment in list.c to point in the right direction if the SysTick
has wrong interrupt priority. It's usually here you end up when
interrupting a critical section with the SysTick.

list.c

@@ -158,6 +158,7 @@ void vListInsert( List_t * const pxList,
         *   4) Using a queue or semaphore before it has been initialised or
         *      before the scheduler has been started (are interrupts firing
         *      before vTaskStartScheduler() has been called?).
+        *   5) Misconfigured SysTick priority? Must be lowest (logical) priority.
         **********************************************************************/
 
         for( pxIterator = ( ListItem_t * ) &( pxList->xListEnd ); pxIterator->pxNext->xItemValue <= xValueOfInsertion; pxIterator = pxIterator->pxNext ) /*lint !e826 !e740 !e9087 The mini list structure is used as the list end to save RAM.  This is checked and valid. *//*lint !e440 The iterator moves to a different value, not xValueOfInsertion. */

portable/CCS/ARM_CM3/port.c

@@ -331,6 +331,9 @@ void vPortExitCritical( void )
 
 void xPortSysTickHandler( void )
 {
+    /* The SysTick is not allowed to interrupt a critical section. */
+    configAssert( uxCriticalNesting == 0 )
+
     /* The SysTick runs at the lowest interrupt priority, so when this interrupt
      * executes all interrupts must be unmasked.  There is therefore no need to
      * save and then restore the interrupt mask value as its value is already

portable/CCS/ARM_CM4F/port.c

@@ -356,6 +356,9 @@ void vPortExitCritical( void )
 
 void xPortSysTickHandler( void )
 {
+    /* The SysTick is not allowed to interrupt a critical section. */
+    configAssert( uxCriticalNesting == 0 )
+
     /* The SysTick runs at the lowest interrupt priority, so when this interrupt
      * executes all interrupts must be unmasked.  There is therefore no need to
      * save and then restore the interrupt mask value as its value is already

portable/GCC/ARM_CM3/port.c

@@ -431,6 +431,9 @@ void xPortPendSVHandler( void )
 
 void xPortSysTickHandler( void )
 {
+    /* The SysTick is not allowed to interrupt a critical section. */
+    configAssert( uxCriticalNesting == 0 )
+
     /* The SysTick runs at the lowest interrupt priority, so when this interrupt
      * executes all interrupts must be unmasked.  There is therefore no need to
      * save and then restore the interrupt mask value as its value is already

portable/GCC/ARM_CM4F/port.c

@@ -493,6 +493,9 @@ void xPortPendSVHandler( void )
 
 void xPortSysTickHandler( void )
 {
+    /* The SysTick is not allowed to interrupt a critical section. */
+    configAssert( uxCriticalNesting == 0 )
+
     /* The SysTick runs at the lowest interrupt priority, so when this interrupt
      * executes all interrupts must be unmasked.  There is therefore no need to
      * save and then restore the interrupt mask value as its value is already

portable/GCC/ARM_CM7/r0p1/port.c

@@ -483,6 +483,9 @@ void xPortPendSVHandler( void )
 
 void xPortSysTickHandler( void )
 {
+    /* The SysTick is not allowed to interrupt a critical section. */
+    configAssert( uxCriticalNesting == 0 )
+
     /* The SysTick runs at the lowest interrupt priority, so when this interrupt
      * executes all interrupts must be unmasked.  There is therefore no need to
      * save and then restore the interrupt mask value as its value is already

portable/IAR/ARM_CM3/port.c

@@ -334,6 +334,9 @@ void vPortExitCritical( void )
 
 void xPortSysTickHandler( void )
 {
+    /* The SysTick is not allowed to interrupt a critical section. */
+    configAssert( uxCriticalNesting == 0 )
+
     /* The SysTick runs at the lowest interrupt priority, so when this interrupt
      * executes all interrupts must be unmasked.  There is therefore no need to
      * save and then restore the interrupt mask value as its value is already

portable/IAR/ARM_CM4F/port.c

@@ -371,6 +371,9 @@ void vPortExitCritical( void )
 
 void xPortSysTickHandler( void )
 {
+    /* The SysTick is not allowed to interrupt a critical section. */
+    configAssert( uxCriticalNesting == 0 )
+
     /* The SysTick runs at the lowest interrupt priority, so when this interrupt
      * executes all interrupts must be unmasked.  There is therefore no need to
      * save and then restore the interrupt mask value as its value is already

portable/IAR/ARM_CM4F_MPU/port.c

@@ -483,6 +483,9 @@ void vPortExitCritical( void )
 
 void xPortSysTickHandler( void )
 {
+    /* The SysTick is not allowed to interrupt a critical section. */
+    configAssert( uxCriticalNesting == 0 )
+
     /* The SysTick runs at the lowest interrupt priority, so when this interrupt
      * executes all interrupts must be unmasked.  There is therefore no need to
      * save and then restore the interrupt mask value as its value is already

portable/IAR/ARM_CM7/r0p1/port.c

@@ -359,6 +359,9 @@ void vPortExitCritical( void )
 
 void xPortSysTickHandler( void )
 {
+    /* The SysTick is not allowed to interrupt a critical section. */
+    configAssert( uxCriticalNesting == 0 )
+
     /* The SysTick runs at the lowest interrupt priority, so when this interrupt
      * executes all interrupts must be unmasked.  There is therefore no need to
      * save and then restore the interrupt mask value as its value is already

portable/MikroC/ARM_CM4F/port.c

@@ -485,6 +485,9 @@ void xPortPendSVHandler( void ) iv IVT_INT_PendSV ics ICS_OFF
 
 void xPortSysTickHandler( void ) iv IVT_INT_SysTick ics ICS_AUTO
 {
+    /* The SysTick is not allowed to interrupt a critical section. */
+    configAssert( uxCriticalNesting == 0 )
+
     /* The SysTick runs at the lowest interrupt priority, so when this interrupt
      * executes all interrupts must be unmasked.  There is therefore no need to
      * save and then restore the interrupt mask value as its value is already

portable/RVDS/ARM_CM3/port.c

@@ -424,6 +424,9 @@ __asm void xPortPendSVHandler( void )
 
 void xPortSysTickHandler( void )
 {
+    /* The SysTick is not allowed to interrupt a critical section. */
+    configAssert( uxCriticalNesting == 0 )
+
     /* The SysTick runs at the lowest interrupt priority, so when this interrupt
      * executes all interrupts must be unmasked.  There is therefore no need to
      * save and then restore the interrupt mask value as its value is already

portable/RVDS/ARM_CM4F/port.c

@@ -516,6 +516,9 @@ __asm void xPortPendSVHandler( void )
 
 void xPortSysTickHandler( void )
 {
+    /* The SysTick is not allowed to interrupt a critical section. */
+    configAssert( uxCriticalNesting == 0 )
+
     /* The SysTick runs at the lowest interrupt priority, so when this interrupt
      * executes all interrupts must be unmasked.  There is therefore no need to
      * save and then restore the interrupt mask value as its value is already

portable/RVDS/ARM_CM7/r0p1/port.c

@@ -503,6 +503,9 @@ __asm void xPortPendSVHandler( void )
 
 void xPortSysTickHandler( void )
 {
+    /* The SysTick is not allowed to interrupt a critical section. */
+    configAssert( uxCriticalNesting == 0 )
+
     /* The SysTick runs at the lowest interrupt priority, so when this interrupt
      * executes all interrupts must be unmasked.  There is therefore no need to
      * save and then restore the interrupt mask value as its value is already