linux-kernel - Re: [RFC][PATCH 4/4] time: Clean up CLOCK_MONOTONIC

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Date:   Fri, 25 Aug 2017 14:16:57 -0700
From:   John Stultz <john.stultz@...aro.org>
To:     Chris Wilson <chris@...is-wilson.co.uk>
Cc:     lkml <linux-kernel@...r.kernel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...nel.org>,
        Miroslav Lichvar <mlichvar@...hat.com>,
        Richard Cochran <richardcochran@...il.com>,
        Prarit Bhargava <prarit@...hat.com>,
        Stephen Boyd <stephen.boyd@...aro.org>,
        Kevin Brodsky <kevin.brodsky@....com>,
        Will Deacon <will.deacon@....com>,
        Daniel Mentz <danielmentz@...gle.com>
Subject: Re: [RFC][PATCH 4/4] time: Clean up CLOCK_MONOTONIC_RAW time handling

On Fri, Aug 25, 2017 at 11:55 AM, John Stultz <john.stultz@...aro.org> wrote:
> I'll look over the code again to see if I can catch anything by
> review. Worse case if we can't get any traction on this in a day or so
> I'll submit a revert.

I think I found the issue. In tk_update_ktime_data() I add the raw_sec
and shifted down  tk->tkr_raw.xtime_nsec to the base. But we already
add the tk->tkr_raw.xtime_nsec to the offset and shift it all down in
the timekeeping_delta_to_ns called from ktime_get_raw, so we
effectively are accumulating the nsecs portion faster then we should.

This only crops up for internal ktime_get_raw() users, but not
getrawmonotonic64() which uses the timespec generation rather then the
ktime method, which is why this wasn't seen by userspace time tests.

I'll send a patch for testing shortly.

thanks
-john