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  1. 27 Jul, 2010 1 commit
    • John Stultz's avatar
      x86: Fix vtime/file timestamp inconsistencies · 8c73626a
      John Stultz authored 
      Due to vtime calling vgettimeofday(), its possible that an application
could call  time();create("stuff",O_RDRW);  only to see the file's
creation timestamp to be before the value returned by time.

A similar way to reproduce the issue is to compare the vsyscall time()
with the syscall time(), and observe ordering issues.

The modified test case from Oleg Nesterov below can illustrate this:

int main(void)
{
	time_t sec1,sec2;
	do {
		sec1 = time(&sec2);
		sec2 = syscall(__NR_time, NULL);
	} while (sec1 <= sec2);

	printf("vtime: %d.000000\n", sec1);
	printf("time: %d.000000\n", sec2);
	return 0;
}

The proper fix is to make vtime use the same time value as
current_kernel_time() (which is exported via update_vsyscall) instead of
vgettime().

Thanks to Jiri Olsa for bringing up the issue and catching bugs in
earlier verisons of this fix.
Signed-off-by: default avatarJohn Stultz <johnstul@us.ibm.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Oleg Nesterov <oleg@redhat.com>
LKML-Reference: <1279068988-21864-2-git-send-email-johnstul@us.ibm.com>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
      8c73626a
  3. 26 Jul, 2010 39 commits
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