Re: [PATCH 2.6] fix POSIX timers expire before their scheduled time

[George Anzinger <george@mvista.com>]

Liu, Hong wrote:
> POSIX says: POSIX timers should not expire before their scheduled time.
> 
> Due to the timer started between jiffies, there are cases that the timer
> will expire before its scheduled time.
> This patch ensures timers will not expire early.
> 
> --- a/kernel/posix-timers.c     2005-03-10 15:46:27.329333664 +0800
> +++ b/kernel/posix-timers.c     2005-03-10 15:50:11.884196136 +0800
> @@ -957,7 +957,8 @@
>                             &expire_64, &(timr->wall_to_prev))) {
>                 return -EINVAL;
>         }
> -       timr->it_timer.expires = (unsigned long)expire_64;
> +       timr->it_timer.expires = (unsigned long)expire_64 + 1;
>         tstojiffie(&new_setting->it_interval, clock->res, &expire_64);
>         timr->it_incr = (unsigned long)expire_64;
> 
Has this happened??  The following code (in adjust_abs_time()) is supposed to 
prevent this sort of thing:

	if (oc.tv_sec | oc.tv_nsec) {
		oc.tv_nsec += clock->res;
		timespec_norm(&oc);
	}

Also, we run rather extensive tests for this sort of thing.


-- 
George Anzinger   george@mvista.com
High-res-timers:  http://sourceforge.net/projects/high-res-timers/