Question

So, this code was working just fine until recently, when we decided to move it to a Lubuntu 12.04 system. The call to timer_settime returns EINVAL, and running it under gdb I’ve confirmed that all of the fields of ts are within 0 and 999999999 at the time that it is called:

1067        if(-1 ==timer_settime(tid,0,&ts,NULL))
(gdb) print ts
$1 = {it_interval = {tv_sec = 0, tv_nsec = 200000000}, it_value = {tv_sec = 0,
tv_nsec = 0}}

Since this should be the only thing that can cause it to return EINVAL I’m very much puzzled. Maybe there’s something obvious here that i’m missing.

struct sigevent sev;
struct itimerspec ts;
timer_t *tid;
//actually point the pointer at something.
tid = calloc(1,sizeof(timer_t));
//make sure there's no garbage in the structures.
memset(&sev,0,sizeof(struct sigevent));
memset(&ts,0, sizeof(struct itimerspec));
//notify via thread
sev.sigev_notify = SIGEV_THREAD;
sev.sigev_notify_function = SwitchThreadHandler;
sev.sigev_notify_attributes = NULL;
sev.sigev_value.sival_ptr = tid;
ts.it_value.tv_sec =0;
ts.it_value.tv_nsec = 0;
ts.it_interval.tv_sec = 0;
ts.it_interval.tv_nsec = 200000000;
if(-1 == timer_create(CLOCK_REALTIME,&sev,tid))
{
    retval = EX_SOFTWARE;
    fprintf(stderr,"Failed to create timer.");
    free(tid);
    return retval;
}

if(-1 ==timer_settime(tid,0,&ts,NULL))
{
    int errsv = errno;
    fprintf(stderr,"timer_settime FAILED!!!\n");
    if(errsv == EINVAL)
    {
        fprintf(stderr,"INVALID VALUE!\n");
    }
    else
    {
        fprintf(stderr,"UNKOWN ERROR: %d\n",errsv);
    }
    return EX_SOFTWARE;
}

Answer 1

timer_settime is documented as taking a timer_t as the first argument, not a timer_t * like timer_create. It will fail with EINVAL if timerid is invalid.

Therefore, you should pass *tid as the first argument.

Note that your compiler should have issued a warning for this.