Re: [Patch] Re: Nasty suprise with uptime

[george anzinger <george@mvista.com>]

Tim Schmielau wrote:
~snip
> @@ -683,6 +683,34 @@
>         if (TQ_ACTIVE(tq_timer))
>                 mark_bh(TQUEUE_BH);
>  }
> +
> +
> +#if BITS_PER_LONG < 48
> +
> +u64 get_jiffies64(void)
> +{
> +       static unsigned long jiffies_hi = 0;
> +       static unsigned long jiffies_last = INITIAL_JIFFIES;
> +       unsigned long jiffies_tmp;
> +
> +       jiffies_tmp = jiffies;   /* avoid races */
> +       if (jiffies_tmp < jiffies_last)   /* We have a wrap */
> +               jiffies_hi++;
> +       jiffies_last = jiffies_tmp;
> +
> +       return (jiffies_tmp | ((u64)jiffies_hi) << BITS_PER_LONG);

Doesn't this need to be protected on SMP machines?  What if two cpus
call get_jiffies64() at the same time...  Seems like jiffies_hi could
get bumped twice instead of once.

George