Changes to core code and port layer:

+ Add configASSERT() into ARM Cortex-M ports to check the number of priority
      bit settings.
    + Clear the 'control' register before starting ARM Cortex-M4F ports in case
      the FPU is used before the scheduler is started.  This just saves a few
      bytes on the main stack as it prevents space being left for a later save
      of FPU registers.
    + Added xSemaphoreGetMutexHolderFromISR().
    + Corrected use of portNVIC_PENDSVSET to portNVIC_PENDSVSET_BIT in MPU ports.

FreeRTOS/Source/queue.c

@@ -567,6 +567,32 @@ static void prvInitialiseNewQueue( const UBaseType_t uxQueueLength, const UBaseT
 #endif
 /*-----------------------------------------------------------*/
 
+#if ( ( configUSE_MUTEXES == 1 ) && ( INCLUDE_xSemaphoreGetMutexHolder == 1 ) )
+
+	void* xQueueGetMutexHolderFromISR( QueueHandle_t xSemaphore )
+	{
+	void *pxReturn;
+
+		configASSERT( xSemaphore );
+
+		/* Mutexes cannot be used in interrupt service routines, so the mutex
+		holder should not change in an ISR, and therefore a critical section is
+		not required here. */
+		if( ( ( Queue_t * ) xSemaphore )->uxQueueType == queueQUEUE_IS_MUTEX )
+		{
+			pxReturn = ( void * ) ( ( Queue_t * ) xSemaphore )->pxMutexHolder;
+		}
+		else
+		{
+			pxReturn = NULL;
+		}
+
+		return pxReturn;
+	} /*lint !e818 xSemaphore cannot be a pointer to const because it is a typedef. */
+
+#endif
+/*-----------------------------------------------------------*/
+
 #if ( configUSE_RECURSIVE_MUTEXES == 1 )
 
 	BaseType_t xQueueGiveMutexRecursive( QueueHandle_t xMutex )