[DragonFlyBSD - Bug #2951] clock_gettime always repots 0 sec, 0 nsec

[bugtracker-admin at leaf.dragonflybsd.org]

Issue #2951 has been updated by zhtw.


This is interesting. When you asked me to doublecheck if clock_gettime works with CLOCK_THREAD_CPUTIME_ID (because you said it works for you), I actually tested it on real kernel. So it does work on real kernel.

But now I'm proceeding with testing ChezScheme (this is how I originally found the bug) on a vkernel, I found out again that it clock_gettime doesn't really work even with CLOCK_THREAD_CPUTIME_ID. It always returns 0 as I reported.

So this there is definitely a bug.

Also, when I proceeded testing ChezScheme, I found another bug, also in clock_gettime, but this time it's present in the real kernel: turned out clock_gettime can return nsec greater than one million:

a at kl:~/tmp$ cat t.c
#include <sys/time.h>
#include <stdio.h>

void busywait()
{
  for (int i = 0; i != 1000000; ++i)
    for (int j = 0; j != 10; ++j)
    ;
}

int main()
{
  struct timespec ts;

  for (int i = 0; i != 1000; ++i) {
    busywait();
    int err = clock_gettime(CLOCK_THREAD_CPUTIME_ID, &ts);
    if (err) {
      printf("err: %d\n", err);
      return 1;
    }
    if (ts.tv_nsec > 1000000000) {
      printf("fatal! nsec = %ld\n", ts.tv_nsec);
      return 1;
    }
  }
}

a at kl:~/tmp$ cc t.c
a at kl:~/tmp$ ./a.out
fatal! nsec = 1007424000

Should I create a separate ticket for this?

----------------------------------------
Bug #2951: clock_gettime always repots 0 sec, 0 nsec
http://bugs.dragonflybsd.org/issues/2951#change-12990

* Author: zhtw
* Status: New
* Priority: Normal
* Assignee: 
* Category: 
* Target version: 
----------------------------------------
When called with CLOCK_PROF, clock_gettime always returns 0 sec, 0 nsec:

$ uname -a
DragonFly kl.zta.lk 4.6-RELEASE DragonFly v4.6.0.10.g16fba-RELEASE #10: Wed Aug 17 14:26:31 CEST 2016     root at kl.zta.lk:/usr/obj/usr/src/sys/X86_64_GENERIC  x86_64
$ cat time.c
#include <sys/time.h>
#include <stdio.h>

int main()
{
  struct timespec ts;
  struct timespec *tp = &ts;

  for (int i = 0; i != 1000000; ++i)
    for (int j = 0; j != 1000; ++j)
      ;

  int err = clock_gettime(CLOCK_PROF, tp);

  printf("err: %d\n", err);

  printf("sec: %ld\n", ts.tv_sec);
  printf("nsec: %ld\n", ts.tv_nsec);
}
$ cc -pedantic -Wall time.c 
$ ./a.out 
err: 0
sec: 0
nsec: 0

The same program on a FreeBSD machine seems to work:
$ uname -a
FreeBSD fbsd 10.1-RELEASE FreeBSD 10.1-RELEASE #0 r274401: Tue Nov 11 21:02:49 UTC 2014     root at releng1.nyi.freebsd.org:/usr/obj/usr/src/sys/GENERIC  amd64
$ cc -pedantic -Wall time.c
$ ./a.out 
err: 0
sec: 1
nsec: 604478000




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