On Tue, 2005-12-06 at 01:01 +0100, [email protected] wrote:
<snip>
> Index: linux-2.6.15-rc5/kernel/hrtimer.c
> ===================================================================
> --- /dev/null
> +++ linux-2.6.15-rc5/kernel/hrtimer.c
<snip>
> +/**
> + * ktime_get_ts - get the monotonic clock in timespec format
> + *
> + * @ts: pointer to timespec variable
> + *
> + * The function calculates the monotonic clock from the realtime
> + * clock and the wall_to_monotonic offset and stores the result
> + * in normalized timespec format in the variable pointed to by ts.
> + */
> +void ktime_get_ts(struct timespec *ts)
> +{
> + struct timespec tomono;
> + unsigned long seq;
> +
> + do {
> + seq = read_seqbegin(&xtime_lock);
> + getnstimeofday(ts);
> + tomono = wall_to_monotonic;
> +
> + } while (read_seqretry(&xtime_lock, seq));
> +
> + set_normalized_timespec(ts, ts->tv_sec + tomono.tv_sec,
> + ts->tv_nsec + tomono.tv_nsec);
> +}
<snip>
unlike many other places I've seen the loop structure:
do {
seq = read_seqbegin(&xtime_lock);
...
} while (unlikely(read_seqretry(&xtime_lock, seq)));
This one lacks the unlikely() in the loop condition. Do high res timers
tend to make the branch hint incorrect?
Thanks,
-Matt Helsley
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