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    SubjectRe: Ktimer / -rt9 (+custom) monotonic_clock going backwards.

    On Wed, 19 Oct 2005, Thomas Gleixner wrote:

    > On Wed, 2005-10-19 at 10:59 -0400, Steven Rostedt wrote:
    > > Hi Thomas,
    > >
    > > I switched my custom kernel timer to use the ktimers with the prio of -1
    > > as you mentioned to me offline. I set up the timer to be monotonic and
    > > have a requirement that the returned time is always greater or equal to
    > > the last time returned from do_get_ktime_mono.
    > >
    > > Now here's the results that I got between two calls of do_get_ktime_mono
    > >
    > > 358.069795728 secs then later 355.981483177. Should this ever happen?
    > Definitely not. monotonic time must go forwards.
    > > I haven't look to see if this happens in vanilla -rt10 but I haven't
    > > touched your ktimer code except for my logging and the patch with the
    > > unlock_ktimer_base (since I was based off of -rt9)
    > The ktimer code itself calls the timeofday code, which provides the
    > monotonic clock. I have no idea what might go wrong.
    > Is this reproducible ?

    FYI, I just merged my changes with -rt13 and everything seems to be
    working very smoothly. I've been running my kernel over an hour without
    showing the backward times. I haven't even added the change from cycle_t
    to be 64 bits.

    So, knock on wood, maybe one of the latest updates fixed the problem. Or
    maybe as soon as I hit send, the machine will crash.

    I'll keep you all posted.

    -- Steve

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