freertos is blocked in vPortSuppressTicksAndSleep function

Question

Hi everyone, 
 I am trying to port freertos on the nRF52832, but it is blocked in the vPortSuppressTicksAndSleep function. Below is the code for configuring the system and the freertos: 
 int main(void)
{
	/*
 * Config hardware peripherals
 */
	ConfigSystem();
	UARTFlush();

	/*
 * Config FreeRTOS
 */
	xMutex = xSemaphoreCreateBinary();
	if(xTaskCreate(TaskTest1, "Task 1", configMINIMAL_STACK_SIZE, NULL, 1, NULL) != pdPASS)
 SystemRunOutOfMemory();
	if(xTaskCreate(TaskTest2, "Task 2", configMINIMAL_STACK_SIZE, NULL, 1, NULL) != pdPASS)
 SystemRunOutOfMemory();

	/*
 * Activate deep sleep mode
 */
	SCB->SCR |= SCB_SCR_SLEEPDEEP_Msk;
 ret_code_t err_code = app_timer_init();
 APP_ERROR_CHECK(err_code);

	// Start FreeRTOS scheduler.
	vTaskStartScheduler();

	while(1)
	{
 PrintError("Forbidden for RTOS status!");
 UARTFlush();
	}
}

void TaskTest1(void * pvParameter)
{
	while(1)
	{
 xSemaphoreTake(xMutex, portMAX_DELAY);
 PrintDebug("Task 1");
 UARTFlush();
 xSemaphoreGive(xMutex);
 vTaskDelay(1);
	}
}

void TaskTest2(void * pvParameter)
{
	while(1)
	{
 xSemaphoreTake(xMutex, portMAX_DELAY);
 PrintDebug("Task 2");
 UARTFlush();
 xSemaphoreGive(xMutex);
 vTaskDelay(1);
	}
}
 
 PrintDebug function: 
 void PrintDebug(const char *string, ...)
{
	volatile char txBuf[100];

	DEBUG_HEADER();
 va_list arg;

 memset((void *) txBuf, 0, sizeof(txBuf));

 va_start(arg, string);
 vsprintf((char *) txBuf, string, arg);
 va_end(arg);
 UARTWrite((uint8_t *) txBuf, strlen((const char *) txBuf));

 COLOR_ENDL();
}

UART_ERR_CODE_t UARTWrite(uint8_t *pByte, uint8_t length)
{
	UART_ERR_CODE_t errCode = UART_ERR_SUCCESS;
	// Write bytes to TX buffer
	errCode |= WriteToTXBuff(pByte, length);

	return errCode;
}

static UART_ERR_CODE_t WriteToTXBuff(uint8_t *byte, uint8_t length)
{
	UART_ERR_CODE_t err = UART_ERR_SUCCESS;
	// If TX buffer is full, return error code
	if(controlBlock.txBufferAvailable == 0)
 return UART_ERR_BYTES_ABORTED;

	// Write bytes to TX buffer until TX buffer is full or all bytes are transmitted
	while((controlBlock.txBufferAvailable != 0) && (length != 0))
	{
 if(xQueueSendToBack(txBuffer, ( void * )byte, (TickType_t) 0) != pdPASS)
 break;
 byte++;
 controlBlock.txBufferAvailable--;
 length--;
	}

	if((controlBlock.txBufferAvailable == 0) && (length != 0))
 err |= UART_ERR_BYTES_ABORTED;

	return err;
}
 
 The code is blocked in the vPortSuppressTicksAndSleep function at the line while (0 == (NVIC->ISPR[0] | NVIC->ISPR[1])) when the program moves to xSemaphoreTake(xMutex, portMAX_DELAY) in TaskTest1 function.