Re: [PATCH] fix for sched_clock() when using jiffies

[Andrew Morton <akpm@linux-foundation.org>]

On Sat, 9 May 2009 05:34:44 +0930
Ron <ron@debian.org> wrote:

>  
> Account for the initial offset to the jiffy count.
> 
> Signed-off-by: Ron Lee <ron@debian.org>
> 
> ---
>  kernel/sched_clock.c |    3 ++-
>  1 files changed, 2 insertions(+), 1 deletions(-)
> 
> diff --git a/kernel/sched_clock.c b/kernel/sched_clock.c
> index a0b0852..a1567b1 100644
> --- a/kernel/sched_clock.c
> +++ b/kernel/sched_clock.c
> @@ -37,7 +37,8 @@
>   */
>  unsigned long long __attribute__((weak)) sched_clock(void)
>  {
> -	return (unsigned long long)jiffies * (NSEC_PER_SEC / HZ);
> +	return (unsigned long long)(jiffies - INITIAL_JIFFIES)
> +					* (NSEC_PER_SEC / HZ);
>  }
>  
>  static __read_mostly int sched_clock_running;

Why?  I assume that you encountered some problem which was fixed
by this patch.  What was that problem?