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SubjectRe: Latency histogram broken after "hrtimer: Set expiry time before switch_hrtimer_base()"
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On Sun, 2014-06-22 at 02:04 +0100, Ben Hutchings wrote: 
> In an rt-kernel with CONFIG_MISSED_TIMER_OFFSETS_HIST enabled,
> __hrtimer_start_range_ns() now crashes, as new_base is not assigned
> before it is used.

Oh yeah, forgot about this.

> I'm not sure how this should be fixed; is it:

My (3.12-ish tree) merge resolution was the later, but it shouldn't
matter which you choose, what's stored where is unchanged pre/post.

> --- a/kernel/hrtimer.c
> +++ b/kernel/hrtimer.c
> @@ -1108,7 +1108,7 @@ int __hrtimer_start_range_ns(struct hrti
>
> #ifdef CONFIG_MISSED_TIMER_OFFSETS_HIST
> {
> - ktime_t now = new_base->get_time();
> + ktime_t now = base->get_time();
>
> if (ktime_to_ns(tim) < ktime_to_ns(now))
> timer->praecox = now;
> --- END ---
>
> or:
>
> --- a/kernel/hrtimer.c
> +++ b/kernel/hrtimer.c
> @@ -1106,6 +1106,11 @@ int __hrtimer_start_range_ns(struct hrti
> #endif
> }
>
> + hrtimer_set_expires_range_ns(timer, tim, delta_ns);
> +
> + /* Switch the timer base, if necessary: */
> + new_base = switch_hrtimer_base(timer, base, mode & HRTIMER_MODE_PINNED);
> +
> #ifdef CONFIG_MISSED_TIMER_OFFSETS_HIST
> {
> ktime_t now = new_base->get_time();
> @@ -1117,11 +1122,6 @@ int __hrtimer_start_range_ns(struct hrti
> }
> #endif
>
> - hrtimer_set_expires_range_ns(timer, tim, delta_ns);
> -
> - /* Switch the timer base, if necessary: */
> - new_base = switch_hrtimer_base(timer, base, mode & HRTIMER_MODE_PINNED);
> -
> timer_stats_hrtimer_set_start_info(timer);
>
> leftmost = enqueue_hrtimer(timer, new_base);
> --- END ---
>
> or something else?
>
> Ben.
>




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