can't mount root disk with ACPI enabled

[Johannes Hofmann]

Johannes Hofmann <johannes.hofmann at gmx.de> wrote:
> Sepherosa Ziehau <sepherosa at gmail.com> wrote:
>> On Tue, May 19, 2009 at 8:23 PM, Johannes Hofmann
>> <johannes.hofmann at gmx.de> wrote:
>>> Sepherosa Ziehau <sepherosa at gmail.com> wrote:
>>>> On Tue, May 19, 2009 at 7:33 PM, Johannes Hofmann
>>>> <johannes.hofmann at gmx.de> wrote:
>>>>> Hi,
>>>>>
>>>>> starting with revision
>>>>>
>>>>> commit 50b53814fb840b70162a846420b75c5bb9432931
>>>>> Author: Sepherosa Ziehau <sephe at dragonflybsd.org>
>>>>> Date:   Sun May 17 13:11:50 2009 +0800
>>>>>
>>>>>    More clock cleanup:
>>>>>
>>>>>    - Move rtc initialization to SI_BOOT2_CLOCKREG, SI_ORDER_FIRST
>>>>>    - Staticize cpu_initclocks()
>>>>>
>>>>>
>>>>> My thinkpad T42 fails to mount the root device with ACPI enabled. When
>>>>> I boot without ACPI it works fine.
>>>>
>>>> Looks like acpi timer is whacked.  Could you do following test:
>>>> set debug.acpi.disabled="timer"
>>>> and boot the problematic kernel?
>>>
>>> This doesn't help. Unfortunately I can't read the complete console
>>> output when it fails...
>> 
>> OK, before I could figure out what's wrong with the reordering, I
>> revert the commit.  Please re-pull HEAD.
> 
> With current HEAD it works fine again - as expected.

Just noticed that even with revision
7e7d17cb48838b48389fb990950f2959b9635e63
I still can't mount the root disk iff I load usb modules (usb, ehci,
umass) during boot via /boot/loader.conf - which I normally don't to
allow CPU to enter C3 state.

So maybe this is just some sort of timing problem?
Is anyone else seeing this? I guess thinkpads are quite common here.

Regards,
Johannes