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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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