Messages in this thread | | | From | Thomas Gleixner <> | Subject | Re: [RFC PATCH v2 2/6] timekeeping: Fix cross-timestamp interpolation corner case decision | Date | Fri, 15 Sep 2023 18:10:29 +0200 |
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On Fri, Aug 18 2023 at 03:20, Peter Hilber wrote: > --- a/kernel/time/timekeeping.c > +++ b/kernel/time/timekeeping.c > @@ -1247,7 +1247,8 @@ int get_device_system_crosststamp(int (*get_time_fn) > */ > now = tk_clock_read(&tk->tkr_mono); > interval_start = tk->tkr_mono.cycle_last; > - if (!cycle_between(interval_start, cycles, now)) { > + if (!cycle_between(interval_start, cycles, now) && > + cycles != interval_start) { > clock_was_set_seq = tk->clock_was_set_seq; > cs_was_changed_seq = tk->cs_was_changed_seq; > cycles = interval_start;
So the explanation in the changelog makes some sense, but this code without any further explanation just makes my brain explode.
This whole thing screams for a change to cycle_between() so it becomes:
timestamp_in_interval(start, end, ts)
and make start inclusive and not exclusive, no?
That's actually correct for both usage sites because for interpolation the logic is the same. history_begin->cycles is a valid timestamp, no?
Thanks,
tglx
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