Re: [PATCH] sched: sched_clock() clocksource handling.

[Daniel Walker <dwalker@fifo99.com>]

On Tue, 2009-06-02 at 16:54 +0900, Paul Mundt wrote:
>  unsigned long long __attribute__((weak)) sched_clock(void)
>  {
> -       return (unsigned long long)(jiffies - INITIAL_JIFFIES)
> -                                       * (NSEC_PER_SEC / HZ);
> +       unsigned long long time;
> +       struct clocksource *clock;
> +
> +       rcu_read_lock();
> +       clock = rcu_dereference(sched_clocksource);
> +       time = cyc2ns(clock, clocksource_read(clock));
> +       rcu_read_unlock();
> +
> +       return time;
>  }

My concerns with the locking here still stand. Nothing you've said or
done bolsters the clocksource in modules argument. I think what your
planning for sh clocksources seems very inelegant. I would imagine a
better solution is out there. I'd prefer if you just leave sched_clock
alone.

Daniel