Re: Hypervisor crash(!) on xl cpupool-numa-split

[Andre Przywara <andre.przywara@amd.com>]

On 02/10/2011 07:42 AM, Juergen Gross wrote:
> On 02/09/11 15:21, Juergen Gross wrote:
>> Andre, George,
>>
>>
>> What seems to be interesting: I think the problem did always occur when
>> a new cpupool was created and the first cpu was moved to it.
>>
>> I think my previous assumption regarding the master_ticker was not too bad.
>> I think somehow the master_ticker of the new cpupool is becoming active
>> before the scheduler is really initialized properly. This could happen, if
>> enough time is spent between alloc_pdata for the cpu to be moved and the
>> critical section in schedule_cpu_switch().
>>
>> The solution should be to activate the timers only if the scheduler is
>> ready for them.
>>
>> George, do you think the master_ticker should be stopped in suspend_ticker
>> as well? I still see potential problems for entering deep C-States. I think
>> I'll prepare a patch which will keep the master_ticker active for the
>> C-State case and migrate it for the schedule_cpu_switch() case.
>
> Okay, here is a patch for this. It ran on my 4-core machine without any
> problems.
> Andre, could you give it a try?
Did, but unfortunately it crashed as always. Tried twice and made sure I 
booted the right kernel. Sorry.
The idea with the race between the timer and the state changing sounded 
very appealing, actually that was suspicious to me from the beginning.

I will add some code to dump the state of all cpupools to the BUG_ON to 
see in which situation we are when the bug triggers.

Regards,
Andre.

-- 
Andre Przywara
AMD-OSRC (Dresden)
Tel: x29712