Dynamic xTaskCreate() doesn't switch to spawned task with higher priority

Kernel
1

jeronimo479 wrote on Wednesday, March 21, 2018:

I’m using FreeRTOS v10.0.0 on an ARM M3 and heap_4.c.

From InitTask() with priority 5 I call:

result = xTaskCreate(
        GPIO_BlinkTask,             // task callback function
        "BlinkTsk",                 // task nickname
        configMINIMAL_STACK_SIZE,   // stack size in words
        NULL,                       // passed parameter
        6,                          // task priority
        NULL);

I expected that the call to xTaskCreate() would leave GPIO_BlinkTask() ready to run, and
therefore, FreeRTOS would switch to it, instead of retruning to InitTask(). I Looked through
xTaskCreate() and could not find any calls to the scheduler. This may or may not be a bug.

The FreeRTOS_Reference_Manual_v9.0.0 states: “Newly created tasks are initially placed in the Ready state, but will immediately become the Running state task if there are no higher priority tasks that are able to run.”

I expected that an RTOS will always have the highest task that is ready to run, running. Since
xTaskCreate() creates GPIO_BlinkTask() ready to run, why is it not immediately running?

I think I can solve this by calling vTaskDelay(0) just after xTaskCreate(GPIO_BlinkTask…)

Thanks,
Wayne

2

jeronimo479 wrote on Wednesday, March 21, 2018:

Please forgive me. I rebuilt all my libraries and source code, and now it works. The FreeRTOSConfig.h files had the max priorites set below the levels I was using, so that the levels were clipped at max, and being equals, there was no task switch after the creation.

Sorry

I would remove this topic if I knew how.