linux-kernel - Re: 2.6.24-rc8 hangs at mfgpt-timer

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Message-ID: <478FE733.2030806@i4.informatik.rwth-aachen.de>
Date:	Fri, 18 Jan 2008 00:39:31 +0100
From:	Arnd Hannemann <hannemann@...informatik.rwth-aachen.de>
To:	Jordan Crouse <jordan.crouse@....com>
CC:	Andres Salomon <dilinger@...ued.net>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: 2.6.24-rc8 hangs at mfgpt-timer

Jordan Crouse schrieb:
> On 17/01/08 23:52 +0100, Arnd Hannemann wrote:
> 
> <snip>
> 
>>> Hmmm - not sure whats happening here.  I wonder if we're stuck in an
>>> interrupt storm of some sort as soon as you register the interrupt handler.
>>> But I would think that whatever was causing the interrupt storm would be
>>> running well before we hit setup_irq(), and you would be recording "nobody
>>> cared" interrupts left and right.
>> Interesting thing is that it hangs not in setup_irq() but later, right
>> after printing the newline of the printk.
> 
> THat makes me think interrupt storm even more.
> 
>>> The thing that scares me is that the TinyBIOS seems to know that we want
>>> to use the MFGPT timers, and I wonder if they did anything behind the scenes
>>> to "help us out" even though we didn't ask for it.
>>>
>>> I don't know how easy it would be for you - but can you try reading 
>>> MSRs 0x51400020 - 0x51400023?   If you need a command line app to do it,
>>> you can use rdmsr from here:
>>>
>>> http://wiki.laptop.org/go/Flashing_LinuxBIOS_on_A-Test_Boards
>> MSR register 0x51400020 => b7:ef:5f:f4:bf:d1:95:68
>> MSR register 0x51400021 => b7:fd:1f:f4:bf:cf:5a:d8
>> MSR register 0x51400022 => b7:f3:bf:f4:bf:f5:fb:a8
>> MSR register 0x51400023 => b7:fb:9f:f4:bf:fd:d9:f8
> 
> Hmmm - those look wrong.  Is /dev/cpu/0/msr there?  The applet on the
> wiki has a bug that doesn't check for it.
I'm sorry, I should have checked: I didn't execute rdmsr as root.
The correct ones:

MSR register 0x51400020 => 00:00:00:00:00:00:0f:00
MSR register 0x51400021 => 00:00:00:00:04:00:00:00
MSR register 0x51400022 => 00:00:00:00:00:00:00:00
MSR register 0x51400023 => 00:00:00:00:00:0c:ba:90

Arnd
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