Unexpected warning

RE: Unexpected warning

Jared — Tue, 17 Nov 2020 12:18:28 GMT

Ok, I'm convinced 🙂

What time period are you using? Could you share your code? You could of course modify the code any way you would like, but it's not recommended, as a consequence can make errors not handled properly.

regards

Jared

RE: Unexpected warning

Malcolm — Tue, 17 Nov 2020 11:45:00 GMT

The following is a workaround that resets the head of the FIFO queue to its original value after the check so that it correctly returns the next item and avoids the call that would return an empty queue message.

/**
* @brief Function for processing user requests.
*
* Function is called only in the context of RTC interrupt.
*/
static void timer_req_process(drv_rtc_t const * const p_instance)
{
    nrf_atfifo_item_get_t fifo_ctx;
    timer_req_t *         p_req;
       bool                                   req = nrf_atfifo_item_check(m_req_fifo, &fifo_ctx);

    while (req)
    {
               m_req_fifo->head.tag = fifo_ctx.last_head.tag;
               m_req_fifo->head.pos.wr = fifo_ctx.last_head.pos.wr;
               m_req_fifo->head.pos.rd = fifo_ctx.last_head.pos.rd;
               p_req = nrf_atfifo_item_get(m_req_fifo, &fifo_ctx);
        switch (p_req->type)
        {

RE: Unexpected warning

Malcolm — Tue, 17 Nov 2020 11:20:13 GMT

I have not tested but this problem with nrf_atfifo_item_check could affect other routines such as in nrf_fstorage_sd.c in the following:

/* Load a new operation from the queue. */
static bool queue_load_next(void)
{
   if (nrf_atfifo_item_check(m_fifo, &m_iget_ctx)) {
    m_p_cur_op = nrf_atfifo_item_get(m_fifo, &m_iget_ctx);

    return (true);
   } else {
       return (false);
   }
}

RE: Unexpected warning

Malcolm — Tue, 17 Nov 2020 10:04:31 GMT

Got it. This version of app_timer2 uses nrf_atfifo_item_check to control the loop, but by using nrf_atfifo_rspace_req it removes the item so preventing getting an item from the fifo.

static void timer_req_process(drv_rtc_t const * const p_instance)
{
    nrf_atfifo_item_get_t fifo_ctx;
    timer_req_t *         p_req;
       bool                                   req = nrf_atfifo_item_check(m_req_fifo, &fifo_ctx);

    while (req)
    {
               p_req = nrf_atfifo_item_get(m_req_fifo, &fifo_ctx);
        switch (p_req->type)
        {

Other versions of timer_req_process do not check and use the call to nrf_atfifo_item_get and its return to control the loop, but this generates a warning on any check.

It appears nrf_atfifo_item_check needs to be corrected so that it does not remove the item from the fifo

RE: Unexpected warning

Malcolm — Tue, 17 Nov 2020 09:54:29 GMT

Apologies It appears there is something else going on.

nrf_atfifo_item_check calls nrf_atfifo_rspace_req the first time and reports there is something in the fifo, but in the second call it reports there is nothing in the fifo.

RE: Unexpected warning

Malcolm — Tue, 17 Nov 2020 09:26:02 GMT

I cannot follow this code:

app_timer_start places a request on the atfifo stack to start a timer. It then requests the timer to do an interrupt that then enacts the request that has been placed on the atfifo stack. So far so good, even if I do not follow the reasoning.

However in the code for timer_req_process I see the line req = nrf_atfifo_item_check(m_req_fifo, &fifo_ctx);, which calls the routine with the address of a variable on the stack that is so far not initialised.

And then in nrf_atfifo_item_check the address of an element in fifo_ctx is passed to another routine. As fifo_ctx is uninitialised it will pass rubbish to the nrf_atfifo_rspace_req routine as the address of last_head.

void * nrf_atfifo_item_get(nrf_atfifo_t * const p_fifo, nrf_atfifo_item_get_t * p_context)
{
if (nrf_atfifo_rspace_req(p_fifo, &(p_context->last_head)))
{

RE: Unexpected warning

Malcolm — Fri, 13 Nov 2020 15:59:03 GMT

I have started from an example but the code is substantially modified. Here is the call stack

nrf_atfifo_item_get
timer_req_process
rtc_irq
RTC1_IRQHandler
<Exception frame>
drv_rtc_irq_trigger
timer_request_proc_trigger
timer_req_schedule
app_timer_start
application_timers_start
ble_device_init
main
[_call_main + 0xd]

I have a similar issue in bsp_button. When a button is pressed it calls a timer, which never calls the timeout routine. It appears nothing is put in the timer queue.

RE: Unexpected warning

Jared — Fri, 13 Nov 2020 14:13:25 GMT

Hi,

I'm not really sure if the error is due to the function call to app_timer_start(). Set a breakpoint where the log is printed, and share the call stack from debug view.

The error is returned if you try to retrieve a char from the FIFO when it's empty.

Are you using an example from the SDK, which one?

regards

Jared