Hard hang with powerd

[Nate Lawson]

Maxim Maximov wrote:
> Bruno Ducrot wrote:
> 
>> On Tue, Sep 20, 2005 at 06:04:40PM +0400, Maxim Maximov wrote:
>>
>>> Bruno Ducrot wrote:
>>>> The 2 logical CPUs need to set the same MSRs at the same time,
>>>> but if the second one is forced to be idle, I'm not sure if p4tcc will
>>>> work fine.
>>>>
>>>> Therefore, I'm wondering if this hard hang happens with a SMP kernel
>>>> and hyperthreading is enabled, or if this happens with a UP kernel.
>>>
>>> Yes, kernel is SMP one.
>>>
>>> # sysctl machdep.hyperthreading_allowed
>>> machdep.hyperthreading_allowed: 1
>>>
>>
>> It's weird.  Could you please try with a kernel without SMP for
>> testing purpose?
>>
> 
> It's fine. Now I'm running UP kernel with 'powerd -v'

Maxim, can you try some debugging things to figure out where the hang is 
happening?  First, add printfs of 1, 2, 3, 4, etc. throughout 
sys/i386/cpufreq/p4tcc.c in p4tcc_set().  Then recompile the SMP kernel 
and boot single user (to save an fsck) and change some settings via 
sysctl dev.cpu.0.freq=xxx until you can get a hang.  See what numbers 
were printed and where it hung.  It should go through all the numbers 
twice when there is no hang since we set a value on cpu0 and cpu1.

Also, see if you can break to the debugger (ctrl-alt-esc) from console 
when it is hung.  I'm guessing no.

-- 
Nate