[GHC] #1933: Zero times in profiling with GHC-6.8.1

[GHC]

#1933: Zero times in profiling with GHC-6.8.1
-------------------------------+--------------------------------------------
 Reporter:  daniel.is.fischer  |          Owner:  simonmar
     Type:  bug                |         Status:  new     
 Priority:  normal             |      Milestone:  6.8.3   
Component:  Profiling          |        Version:  6.8.1   
 Severity:  normal             |     Resolution:          
 Keywords:                     |     Difficulty:  Unknown 
 Testcase:                     |   Architecture:  x86     
       Os:  Linux              |  
-------------------------------+--------------------------------------------
Comment (by daniel.is.fischer):

 I don't really know what I'm doing, but after digging in a number of
 header files I did not understand, I got this programme:
 {{{
 #include <stdio.h>
 #include <stdlib.h>
 #include <time.h>
 #include <signal.h>
 #include <unistd.h>
 static volatile int tock = 0;
 static void handler(int i)
 {
    tock = 1;
 }

 int main(int argc, char *argv[])
 {

     struct sigevent ev;
     timer_t timer;
     struct itimerspec it;
     struct sigaction action;
     unsigned int i;
     int m,n,count = 0;

     ev.sigev_notify = SIGEV_SIGNAL;
     ev.sigev_signo  = SIGVTALRM;
     printf("%u\n",i);
     printf("Random timer is %d\n",timer);
     printf("Getting time\n");
     m = timer_gettime(timer,&it);
     printf("Resulted in %d\n",m);
     printf("Timer says: interval is %lld, %ld,\nvalue is %lld, %ld\n"
             ,(long long)it.it_interval.tv_sec,it.it_interval.tv_nsec
             ,(long long)it.it_value.tv_sec,it.it_value.tv_nsec);
     printf("timer is %d after first gettime\n",timer);
     if (timer_create(CLOCK_PROCESS_CPUTIME_ID, &ev, &timer) != 0) {
         printf("No CLOCK_PROCESS_CPUTIME_ID timer\n");
        exit(1);
     }
     printf("timer created with CLOCK_PROCESS_CPUTIME_ID is %d\n",timer);
     for(n = 3; n < 20000; n++){
         for(m = 2; m <= n/2; m++){
             if (!(n%m)) count++;
         }
     }
     printf("%d divisors\n",count);
     printf("Getting time\n");
     m = timer_gettime(timer,&it);
     printf("Resulted in %d\n",m);
     printf("Timer says: interval is %lld, %ld,\nvalue is %lld, %ld\n"
             ,(long long)it.it_interval.tv_sec,it.it_interval.tv_nsec
             ,(long long)it.it_value.tv_sec,it.it_value.tv_nsec);
     printf("timer now is %d\n",timer);
     if (timer_create(CLOCK_REALTIME, &ev, &timer) != 0) {
         printf("No CLOCK_REALTIME timer\n");
        exit(2);
     }
     printf("timer created with CLOCK_REALTIME is %d\n",timer);
     printf("Getting time\n");
     m = timer_gettime(timer,&it);
     printf("Resulted in %d\n",m);
     printf("Timer says: interval is %lld, %ld,\nvalue is %lld, %ld\n"
             ,(long long)it.it_interval.tv_sec,it.it_interval.tv_nsec
             ,(long long)it.it_value.tv_sec,it.it_value.tv_nsec);
     printf("timer now is %d\n",timer);
     for(n = 3; n < 20000; n++){
         for(m = 2; m <= n/2; m++){
             if (!(n%m)) count++;
         }
     }
     printf("%d divisors\n",count);
     printf("Getting time\n");
     m = timer_gettime(timer,&it);
     printf("Resulted in %d\n",m);
     printf("Timer says: interval is %lld, %ld,\nvalue is %lld, %ld\n"
             ,(long long)it.it_interval.tv_sec,it.it_interval.tv_nsec
             ,(long long)it.it_value.tv_sec,it.it_value.tv_nsec);
     printf("timer finally is %d\n",timer);

     action.sa_handler = handler;
     action.sa_flags = 0;
     sigemptyset(&action.sa_mask);
     if (sigaction(SIGVTALRM, &action, NULL) == -1) {
         printf("SIGVTALRM problem\n");
         exit(3);
     }

     it.it_value.tv_sec = 0;
     it.it_value.tv_nsec = 1;
     it.it_interval = it.it_value;
     if (timer_settime(timer, 0, &it, NULL) != 0) {
         printf("settime problem\n");
         exit(4);
     }

     usleep(100);
     if (tock) exit(0);
     exit(5);
     return 0;
     exit(0);
 }
 }}}
 and from that the output
 {{{
 dafis at linux:~/Documents> gcc -Wall -o timerTest Timertest.c -lrt
 dafis at linux:~/Documents> ./timerTest
 134513370
 Random timer is 1075293183
 Getting time
 Resulted in -1
 Timer says: interval is 1075248004, -1073745532,
 value is 1074079461, 1075321808
 timer is 1075293183 after first gettime
 timer created with CLOCK_PROCESS_CPUTIME_ID is 0
 161150 divisors
 Getting time
 Resulted in 0
 Timer says: interval is 0, 0,
 value is 0, 0
 timer now is 0
 timer created with CLOCK_REALTIME is 1
 Getting time
 Resulted in 0
 Timer says: interval is 0, 0,
 value is 0, 0
 timer now is 1
 322300 divisors
 Getting time
 Resulted in 0
 Timer says: interval is 0, 0,
 value is 0, 0
 timer finally is 1
 dafis at linux:~/Documents>
 }}}
 So if I interpret this right, timer_create does work, but timer_gettime
 doesn't.

 If you give me a good lead, I can investigate further, but I know
 practically nothing about the C-libs, so please be detailed.

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/1933#comment:14>
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