FreeRTOS Queues seem broken.

[maxv]

Hi,

The xQueueReceive function in FreeRTOS seems to be broken, when a non-zero timeout is specified.

Example, I'm trying to create and ordered output mechanism for the UART using a task and a FIFO queue:

static void uart_output_task(void * arg)
{
    for (;;)
    {
        struct SerialPortOutput spo;

        printf("uart_output_task: Waiting for data to send, come on.\n");
        
        // Block waiting on data in the queue.
        if (xQueueReceive(m_uart_output_queue, &spo, 100))
        {
            printf("Sending data to UART.\n");
            
            // Send data to UART.
            nrf_drv_uart_tx(spo.output, spo.length);
        }
        else
        {
            printf("uart_output_task: xQueueReceive had nothing to send.\n");
        }
        
        // char test[8] = "test\r\n";
        // nrf_drv_uart_tx(test, 6);
    }
}

If I specify a timeout to the xQueueReceive method (in this case 100 ticks), the task prints the first printf() and stops forever while waiting. I should be seeing that printf() every 100 ticks. If I set the queue receive timeout to 0, it loops appropriately, but this is of course not the behavior I want. This also happens if I set it to portDELAY_MAX.

Thanks, Max

[maxv]

Unbelievable. The problem was that the default configTOTAL_HEAP_SIZE

#define configTOTAL_HEAP_SIZE                                                     ( 4096 )

Breaks after only 2 user tasks have been implemented. Trying to start a third task causes vTaskStartScheduler to fail.

Reconfiguring this, for now, to:

#define configTOTAL_HEAP_SIZE                                                     ( 8192 )

Fixes the problem.

So it's not a problem in the Queue. Thanks for the help guys.

Here's the sample code with gdb trace:

/**@brief Function for application main entry.
 */
int main(void)
{
    // Do not start any interrupt that uses system functions before system initialisation.
    // The best solution is to start the OS before any other initalisation.

    // Init a semaphore for the BLE thread.
    m_ble_event_ready = xSemaphoreCreateBinary();

    if(NULL == m_ble_event_ready)
    {
        APP_ERROR_HANDLER(NRF_ERROR_NO_MEM);
    }
    
    m_uart_output_queue = xQueueCreate(5, sizeof (struct SerialPortOutput));
    
    if (m_uart_output_queue)
    {
        printf("UART output queue created successfully!\n");
    }
    else
    {
        printf("UART output queue could not be created!\n");    
    }

    // Start execution.
    if(pdPASS != xTaskCreate(ble_stack_thread, "BLE", 256, NULL, 1, &m_ble_stack_thread))
    {
        APP_ERROR_HANDLER(NRF_ERROR_NO_MEM);
    }

    nrf_drv_uart_config_t uart_config = NRF_DRV_UART_DEFAULT_CONFIG;

    if (NRF_SUCCESS == nrf_drv_uart_init(&uart_config, uart_event_handler))
    {
        printf("UART initialized properly.\n");
    }
    else
    {
        printf("UART failed to initialize properly.\n");
    }
    
    if (pdPASS != xTaskCreate(uart_output_task, "UART Output Task", 256, NULL, 1, &m_uart_output_thread))
    {
        printf("Out of memory.");
        APP_ERROR_HANDLER(NRF_ERROR_NO_MEM);
    }

    if (pdPASS != xTaskCreate(uart_test_task, "Test UART Task", 256, NULL, 1, &m_uart_test_task))
    {
        printf("Out of memory.");
        APP_ERROR_HANDLER(NRF_ERROR_NO_MEM);
    }
    
    /* Activate deep sleep mode */
    // SCB->SCR |= SCB_SCR_SLEEPDEEP_Msk;

    // Start FreeRTOS scheduler.
    vTaskStartScheduler();

    while (true)
    {
        printf("Oops.\n");
        APP_ERROR_HANDLER(NRF_ERROR_FORBIDDEN);
    }
}

gdb output is:

Breakpoint 1, main () at /home/max/nRF5_SDK_11.0.0_89a8197/examples/ble_peripheral/ble_app_hrs_freertos/main.c:1205
1205	{

(gdb) break vTaskStartScheduler
Breakpoint 2 at 0x1e2c0: file /home/max/nRF5_SDK_11.0.0_89a8197/external/freertos/source/tasks.c, line 1544.
(gdb) continue
Continuing.

Breakpoint 2, vTaskStartScheduler () at /home/max/nRF5_SDK_11.0.0_89a8197/external/freertos/source/tasks.c:1544
1544	{
(gdb) n
1552			xReturn = xTaskCreate( prvIdleTask, "IDLE", tskIDLE_STACK_SIZE, ( void * ) NULL, ( tskIDLE_PRIORITY | portPRIVILEGE_BIT ), &xIdleTaskHandle ); /*lint !e961 MISRA exception, justified as it is not a redundant explicit cast to all supported compilers. */
(gdb) n
1565				xReturn = xTimerCreateTimerTask();
(gdb) n
1574		if( xReturn == pdPASS )
(gdb) n
main () at /home/max/nRF5_SDK_11.0.0_89a8197/examples/ble_peripheral/ble_app_hrs_freertos/main.c:1304
1304	        printf("Oops.\n");
(gdb)