Messages in this thread | | | Date | Thu, 27 Jul 2023 12:21:38 +0200 | From | Peter Hilber <> | Subject | Re: [RFC PATCH 1/7] timekeeping: Fix cross-timestamp interpolation on counter wrap |
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On 08.07.23 00:51, John Stultz wrote: > On Fri, Jun 30, 2023 at 10:12 AM Peter Hilber > <peter.hilber@opensynergy.com> wrote: >> >> cycle_between() decides whether get_device_system_crosststamp() will >> interpolate for older counter readings. >> >> cycle_between() yields wrong results for a counter wrap-around where after >> < before < test, and for the case after < test < before. >> >> Fix the comparison logic. >> >> Fixes: 2c756feb18d9 ("time: Add history to cross timestamp interface supporting slower devices") >> Signed-off-by: Peter Hilber <peter.hilber@opensynergy.com> >> --- >> kernel/time/timekeeping.c | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c >> index 266d02809dbb..8f35455b6250 100644 >> --- a/kernel/time/timekeeping.c >> +++ b/kernel/time/timekeeping.c >> @@ -1186,7 +1186,7 @@ static bool cycle_between(u64 before, u64 test, u64 after) >> { >> if (test > before && test < after) >> return true; >> - if (test < before && before > after) >> + if (before > after && (test > before || test < after)) >> return true; >> return false; >> } > > Thanks for catching this and sending it in. > Looks good to me. Curious: Did you actually hit such a wrap around with u64s?
No, I just saw this when fixing the bug in the next patch.
Thanks,
Peter
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