Question

I’m trying to use a POSIX timer, but my code can’t run.

timer_t id_timer_;

// some code. timer_create(), etc.

void timerPeriod (unsigned long sec, unsigned long nsec)
{
  struct itimerspec myperiod;
  myperiod.it_interval.tv_sec = sec;
  myperiod.it_interval.tv_nsec = nsec;
  myperiod.it_value.tv_sec = sec;
  myperiod.it_value.tv_nsec = nsec;

  if (timer_settime (&id_timer_, 0, &myperiod, 0))
    perror("timer_settime");
}

It returns timer_settime: Invalid argument, while arguments are looking good to me.

I also tried timer_settime(id_timer_, 0, &myperiod, 0) (without the & before id_timer_), which I think is the good way to use timer_settime() : segmentation fault…

Any clue ?

Answer 1

In ordre to create the timer, the struct sigaction must be properly set.

struct sigaction sa;
sa.sa_flags = SA_SIGINFO;
sa.sa_sigaction = your_handler;

In my previous code, sa_flags was set to 0 instead of SA_SIGINFO.

More info on kernel.org