Tasks blocked after using xQueueReceive

Kernel
1

Hi Everyone, I am new to using freeRTOS and i was setting up my project to demonstrate inter task comms using queues. I am unable to understand the nature of the issue. Basically the tasks stops from executing if i read from queue. My code is as follows:

main.c

	atmel_start_init();
	printf( "initializing all threads\n");
    
	xTaskCreate(     mdrMngTask,
                    "MDR_MANAGEMENT_TASK",
                    configMINIMAL_STACK_SIZE*2,
                    NULL,
                    0,
                    NULL );
    
	xTaskCreate(     timeMngTask,
                    "TIME_MANAGEMENT_TASK",
                    configMINIMAL_STACK_SIZE,
                    NULL,
                    0,
                    NULL );
	
	printf("Starting the scheduler\n");

    /* Start the tasks and timer running. */
    vTaskStartScheduler();

    for( ;; )
       printf("Stuck in main\n");

mdr_mng_task.c

void mdrMngTask( void *pvParameters )
{
	TickType_t xNextWakeTime;
	printf("mdrMngTask started \n");
    xNextWakeTime = xTaskGetTickCount();
	uint8_t count=1;
    for( ;; )
    {
        printf("MM - start\n");
        vTaskDelay(mdr_MANAGEMENT_PERIOD_MS/1.5);
        printf("MM - delayed\n");
		tm_addToQueue(&count);
		count++;
		printf("MM - running\n");
    }
}

time_mng_task.c

QueueHandle_t q_timeMngQueue;

uint8_t tm_addToQueue(uint8_t *value)
{
	if ( xQueueSend(q_timeMngQueue,value,0) == pdTRUE )
    {
        printf("TM_q - %d @ %d\n",*value, (uxQueueSpacesAvailable(q_timeMngQueue)+1));
        return pdTRUE ;
    }
    else
    {
        printf("q_full\n");
        return errQUEUE_FULL;
    }
}
void timeMngTask( void *pvParameters )
{
	printf("timeMngTask started \n");

    q_timeMngQueue = xQueueCreate( 10, sizeof(uint8_t));
    uint8_t buffer;
    for( ;; )
    {
		printf("TM - start\n");
		vTaskDelay(timer_MANAGEMENT_PERIOD_MS/2);
        printf("TM - delayed\n");
        if(xQueueReceive(q_timeMngQueue, &buffer, ( TickType_t ) 10) == pdTRUE)
        {
            printf("TM - recv - %d\n",buffer);
            printf("TM_q - %d\n",uxQueueSpacesAvailable(q_timeMngQueue));
        }    
        else
            printf("TM - timed out\n");

        printf("TM - running\n");		
        
    }
}

If i compile and run this code i get following output:

“7/08/2024 11:26:18 AM”,initializing all threads
“7/08/2024 11:26:18 AM”,Starting the scheduler
“7/08/2024 11:26:18 AM”,mdrMngtimeMnTask sgTask tartedstarte
“7/08/2024 11:26:18 AM”,MM -d
“7/08/2024 11:26:18 AM”,TM start- star
“7/08/2024 11:26:18 AM”,t
“7/08/2024 11:26:21 AM”,TM - delayed
“7/08/2024 11:26:21 AM”,TM - timed out
“7/08/2024 11:26:21 AM”,TM - running
“7/08/2024 11:26:21 AM”,TM - start
“7/08/2024 11:26:23 AM”,MM - delayed
“7/08/2024 11:26:23 AM”,TM_q - 1 @ 10
“7/08/2024 11:26:23 AM”,MM - running
“7/08/2024 11:26:23 AM”,MM - start
“7/08/2024 11:26:25 AM”,TM - delayed
“7/08/2024 11:26:25 AM”,TM - recv - 1
“7/08/2024 11:26:25 AM”,TM_q - 10
“7/08/2024 11:26:25 AM”,TM - running
“7/08/2024 11:26:25 AM”,TM - start

After this the rtos appears to be halted forever. You can notice from this that its stuck at vTaskDelay. How can i enable more debugging or resolve this issue.

Another thing i have noticed is that if i comment out the following section from time_mng_task.c

        if(xQueueReceive(q_timeMngQueue, &buffer, ( TickType_t ) 10) == pdTRUE)
        {
            printf("TM - recv - %d\n",buffer);
            printf("TM_q - %d\n",uxQueueSpacesAvailable(q_timeMngQueue));
        }    
        else
            printf("TM - timed out\n");

The mdr_mng_task is able to consistently store info into the queue until it gets full.

2

I doubt that the stack sizes are sufficient. You should enable FreeRTOS - stacks and stack overflow checking and define configASSERT for development.
printf family functions usually require quite a lot of stack.
Also the ‘%d’ format specifier probably doesn’t match your uint8_t input. This may or may not work as expected.

1 Like
3

Hi hs2,

I couldnt figure out how to implement stack overflow checking, however, i increased my stack size of timeMngTask to twice of what it was and now its working. Thank you for your help.

Change:

	xTaskCreate(     timeMngTask,
                    "TIME_MANAGEMENT_TASK",
                    configMINIMAL_STACK_SIZE*2,
                    NULL,
                    0,
                    NULL );
4

Thank you for reporting back!

5

You can read more about stack overflow checking here

1 Like