On 09/09/2015 03:29 PM, Konstantinos Chalas wrote:
> For future reference, this is what a working POSIX timer in Xenomai
> looks like:
>
Good you got it working. A few additional hints:
> void* print_time (void* args)
> {
> struct timespec tp;
> char buffer [80];
> struct itimerspec new_value, old_value;
> struct sigaction action;
> struct sigevent sevent;
> sigset_t set;
> int signum = SIGALRM;
>
> sevent.sigev_notify = SIGEV_THREAD_ID;
> sevent.sigev_notify_thread_id = syscall(__NR_gettid);
> sevent.sigev_signo = signum;
>
Passing a NULL sigevent will get you the exact same behavior, i.e.:
signum=SIGALRM, SIGEV_THREAD_ID to the calling thread. With the proper
fix mentioned earlier, that is.
> sigemptyset(&set);
> sigaddset(&set, signum);
> sigprocmask(SIG_BLOCK, &set, NULL);
This masking is useless, and do not apply to Xenomai/cobalt signals but
to regular ones. Cobalt signals are synchronous only, so you won't
receive any async notification via some handler. sigwait*() is required
to pull the pending signals explicitly. You can see this as all signals
managed by Cobalt being implicitly blocked for any rt thread - of
course, this does not apply to regular Linux signals which behave as usual.
> while(1){
> /* wait for signal (1 s) */
> if (sigwait (&set, &signum) == -1)
> perror ("sigwait");
sigwait() does not return -1, but a positive error number if something
went wrong.
>
> if (clock_gettime (CLOCK_MONOTONIC, &tp) == -1)
> perror ("clock_gettime");
>
> sprintf (buffer, "%ld s %ld ns overrun = %d\n", tp.tv_sec,
> tp.tv_nsec, timer_getoverrun (timer1));
Another way to retrieve the count of overruns for a timer without the
extra call is to invoke sigwaitinfo(&set, &siginfo), fetching that value
from siginfo.si_overrun.
--
Philippe.
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