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    SubjectRe: One-shot high-resolution POSIX timer periodically late
    Ingo Molnar wrote:

    > John wrote:
    >
    >> Ingo Molnar wrote:
    >>
    >>> 2.6.18-rt7 is pretty old, do you see the problem in 2.6.20-rc6-rt5 too?
    >>
    >> Ingo, Thomas,
    >>
    >> I cannot reproduce in 2.6.20-rc6-rt6, but it is not strictly an
    >> apples-to-apples comparison because I get a tsc clocksource in
    >> 2.6.20-rc6-rt6, and an acpi_pm clocksource in 2.6.18.6-rt7.
    >
    > That suggests that the TSC was not deemed reliable by the newer kernel,
    > which almost always means it's not realiable. I think the problems you
    > were seeing are consistent with TSC being non-monotonic - so the fix is
    > to not use the TSC - and the newer kernel does this automatically.

    Ingo,

    Perhaps you've mis-read my message?

    *2.6.18.6-rt7* installed an acpi_pm clocksource. When I used a boot
    parameter to force the clocksource to tsc, the high-resolution timer
    infrastructure broke (timers expired several *ms* too late).

    On the other hand, *2.6.20-rc6-rt6* and *2.6.20-rt2* both installed a
    tsc clock source, and it works.

    Therefore, it is not the newer kernel that ignored the tsc, but the
    older kernel. Thus I don't know what to make of your comment :-)

    Regards,

    John

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