Running out of scheduler's queue size with app_timer

[andrey]

I've been experiencing this bug for a while now. What happens is that a app_timer's overflow handler can't put any more messages into the queue because the queue is full, which is surprising considering my queue size is 15.

I run two userspace timers using the app_timer module.

This is the function call order:

timeout_handler_exec() -> app_timer_evt_schedule() -> app_sched_event_put() -> app_sched_queue_full() == true -> next_index(index) == m_queue_size == 15

My APP_TIMER_OP_QUEUE_SIZE is 5 (not sure if this one matters), SCHED_QUEUE_SIZE is 15.

Now I'm just hoping that someone has run into this issue and solved it because I know that my explanation is lacking.

[Simon Third]

Hi Andrey,

This is likely because you have some normal level code that is taking to much run time before getting back to app_sched_execute();

For me this happened when I had long sequences of printf() strings.

Also, it's not uncommon to need a schedule queue size of 30-40 when there is a lot of activity.

In my case I added another call to app_sched_execute() in fputc() when the UART buffer was full.

Simon.

[andrey]

Yeah, I do have a function in userspace which takes ~10s to return, so that's probably it. Do you know how this happens exactly?

[Simon Third]

You need to break down your tasks/functions to take no longer than say 5-10ms of run time before app_sched_execute() can run again. Do this by breaking down your processing into tasks which you can PUT onto the scheduler queue. One way to do this is setup a processing state machine and have it run from a repeating timer (which you can stop and restart later if needed). I do this to run LEDs when things like flashing is required.

In general you need generate and process everything as an event.

S3

[andrey]

That sounds like an extremely limiting design requirement which would require a complete rewrite of the project and isn't even motivated by any "real" reason :/. So do I understand it correctly that if a timer handler isn't called before another timer event happens, it just adds this new event to the queue?

[Jeezhao]

i has run into this problem,i not use app_shedue_excute. APP_TIMER_INIT(APP_TIMER_PRESCALER, APP_TIMER_MAX_TIMERS, APP_TIMER_OP_QUEUE_SIZE, false); . do you resolve this better way? tell me! thanks