Julian:
Given your example I am a bit confused about some things. I think part of my
confusion is that you intialized the idle task to priority 1 and the other task
to priority 2. Priority 1 is higher priority than 2. I guess idle task to me is
something special but I realize this could just be an example name. So I will
go with the presumption that the priorities you have specified are correct:
idle_task_handler is the highest priority task and proc_task_handler is a task
lower in priority.
The other part of this example that confuses me is what happens in
some_event(). I presume that this function is waiting for some event to occur
and it is yielding if no event is available. If it is not, you will never yield
and you will be stuck in that task forever (and that does not have anything to
do with the order of initialization as far as I can see). If that call does
yield, I do not see the problem.
Anyway, and I probably should have said this first, yes, you have to be careful
about the order in which things are initialized. This does indeed get tricky at
times but should be possible given that sysinit has stages of initialization
and can be used to make sure that data structures are initialized prior to them
being called.
Just an FYI. I realize that you are just showing example code and probably
typed this up quickly, but just in case… I would not do the following: assert(
func_call() == OK ). This is because assert may get defined out and then you
are not making that function call. Better to do this:
rc = func_call();
assert(rc == OK);
I have been burnt by this in the past so I wanted to point it out.
> On May 11, 2017, at 2:41 AM, Julian Ingram <julian.ing...@imgtec.com> wrote:
>
> Hi all,
>
> Having moved the PIC32 port to the newer start-up method where os_start is
> called before main, there have been problems with a tick potentially
> occurring between task initialisations.
>
> Am I missing something here? If not, what is the standard fix, just be
> careful about the order of task initialisation, initialise them a critical
> section or?
>
> For example:
>
> void
> idle_task_handler(void *arg)
> {
> while (1) {
> if (some_event()) {
> os_sem_release(&sem);
> }
> }
> }
>
> void
> proc_task_handler(void *arg)
> {
> while (1) {
> int err = os_sem_pend(&sem, OS_TIMEOUT_NEVER);
> // ...
> }
> }
>
> int
> main(int argc, char **argv)
> {
> sysinit();
> assert(os_sem_init(&sem, 0) == OS_OK);
> os_task_init(&idle_task, "idle", idle_task_handler, NULL, 1, OS_WAIT_FOREVER,
> idle_stack, IDLE_STACK_SIZE);
> // if a systick happens here I'm stuck in the idle task
> forever.
> os_task_init(&proc_task, "proc", proc_task_handler, NULL, 2,
> OS_WAIT_FOREVER, proc_stack, PROC_STACK_SIZE);
> }
>
> Thanks,
>
> Julian Ingram
> Software Design Engineer
> MIPS Platforms
> Imagination Technologies Limited
> t: +44 (0)113 2429814
> www.imgtec.com<http://www.imgtec.com/>
>
