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SubjectRe: HPET regression in 2.6.26 versus 2.6.25 -- connection between HPET and lockups found


> Just to make sure: on a working kernel, do you get the HPET messages?
> I.e. does the hpet truly work in that case?

On the "fileserver", where 2.6.25 works but 2.6.26 locks up, the HPET
_does_ work on a working kernel:

$ uname -r
2.6.26.revert1

$ dmesg | grep -i hpet
ACPI: HPET 77FE80C0, 0038 (r1 RS690 AWRDACPI 42302E31 AWRD 98)
ACPI: HPET id: 0x10b9a201 base: 0xfed00000
hpet clockevent registered
hpet0: at MMIO 0xfed00000, IRQs 2, 8, 0, 0
hpet0: 4 32-bit timers, 14318180 Hz
hpet_resources: 0xfed00000 is busy


What I didn't realize is that the "desktop" machine, where 2.6.26 has
always "worked", does NOT have a working HPET after all, even though
I have enabled all HPET options in .config:

$ uname -r
2.6.26.080801.desktop.uvesafb

$ dmesg | grep -i hpet
$


This means I misunderstood my situation on "desktop". I believed HPET
was working on all of my machines, but now I am not certain that it
ever worked on "desktop" since I built it (May 2007). The question
never arose before, and because I enabled the HPET option in .config,
I just assumed that HPET was working. (Duh...) I failed to look into
this until now.

At any rate, my subject line is still accurate: there _is_ an HPET
regression on "fileserver" (and "webserver"), since it worked on
2.6.25 kernels but causes lockups on 2.6.2[67] kernels.

(I don't know what is going on with "desktop": does the motherboard
lack HPET, or does the Linux kernel not support the HPET hardware on
the motherboard?)

BTW: the 'dmesg' output above is the same on "desktop" with 2.6.25
and 2.6.26 -- I just checked to be sure. For "fileserver", I checked
an old 2.6.25 kernel just now, and the output is identical.


Another experiment: I just tried this...

static __init int hpet_insert_resource(void)
{
- if (!hpet_res)
+ /* if (!hpet_res) */
return 1;

- return insert_resource(&iomem_resource, hpet_res);
+ /* return insert_resource(&iomem_resource, hpet_res); */
}

... and the lock up still occurs. So, the memory is allocated but
the resource info is not inserted into the tree. Whether the
dynamic memory for hpet_res is being damaged or not has no bearing
on the lockups, it would seem. Looks like I was barking up the
wrong tree....


Dave W.


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