Kernel clock issue "Clocksource tsc unstable"

[NoOp]

On 02/27/2009 06:55 PM, Rashkae wrote:
> NoOp wrote:
> 
>> I recall that thread:
>> http://comments.gmane.org/gmane.linux.ubuntu.user/145397
>> [Computer loosing time]
>> might be worth looking at again.
>> 
>>
> 
> Not really,, That thread led me to believe the problem was with my power
> supply, which I replaced, and declared success.  However, my success was
> very short lived.  It was afterwards that I discovered I can fix it by
> changing my clocksource from tsc to acpm, but this was something so
> obscure, (and it seemed, not bothering anyone else) that I never
> bothered posting about it.
> 

But shouldn't it switch automatically to acpi_pm if tsc is not stable?[1]

For instance, on the Thinkpad A21M that I receive the dmesg of:
Clocksource tsc unstable (delta = -87685142 ns)

I see in BIOS that the sytstem date is OK, but the actual system time is
03:03:24 (UTC) (note it's showing the proper time in Ubuntu) - hence the
'Clocksource tsc unstable' msg. If I actually set it to that time
(Local) in BIOS and then reboot & check dmesg again, I now see:

Clocksource tsc unstable (delta = -1984279121 ns)

Current clocksource on that machine is acpi_pm with no mods to
menu.list. It's a fairly new install (hardy) so something in the
kernel/boot has decided on it's own to not use tsc.

Anyway... It's all still a mystery to me :-)