nRF5 FreeRTOS main stack reused

[genis]

I am using the FreeRTOS port included in a nRF52832 with nRF5 v11.0.0 + s132. From main() I create a task and I pass it some input data as argument. That data is encapsulated in a struct which I declare in the stack of the main function. When the recover that data from the task I create, the data is corrupted/invalid. Something like this:

typedef struct {
    ...
} task_arg_t;

void task(void *args) {
    task_arg_t task_args = (task_arg_t *)  args;
    /* At this point, the data in task_args is invalid */
    while (1) { ... }
}

void main() {
    task_arg_t args;
    ble_task_handle hndl;
    /* Populate args */
    ....
    xTaskCreate(task, "Task name", 256, 1, &hndl)
    vTaskStartScheduler();
    /*  vTaskStartScheduler only returns if insufficient heap */
    APP_ERROR_HANDLER(NRF_ERROR_NO_MEM);
 }

If I declare task_arg_t args in main() in the heap by declaring it as static then the data I recover in the task is right and valid. I researched and I read that depending on the port the stack of main() may be reused internally by the ISRs. It appears to me that this is what is happening here.

Can anyone confirm that? Otherwise, is there any other reasonable explanation for that happening?

[Susheel Nuguru]

This is nothing to do with the Nordic port of UART. The stack of main and the stack of your newly created task are different. You cannot pass stack memory to the created task because now you assume that the main stack remains untouched at the time your task gets to running state. The first chapter of FreeRTOS tells you to declare static if you want to exchange bulk information in between tasks. Also I do not see anything wrong in declaring your task_arg_t args as static outside main.

[genis]

I think there is a misunderstanding, I am not using the ISR. Anyway I was assuming what I declared in the stack in main() didn't get modified, which is obviously wrong here. I'll declare it in the heap, but I wanted to know why that was happening. Thanks.