linux-kernel - Re: [APIC] Kernel panic, rsync corruption, intel q8200, 2.6.28-rc8

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Date:	Mon, 09 Feb 2009 18:50:35 -0500
From:	Sam Ruby <rubys@...ertwingly.net>
To:	Len Brown <lenb@...nel.org>
CC:	Thomas Gleixner <tglx@...utronix.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>, linux-acpi@...r.kernel.org,
	x86@...nel.org, "Maciej W. Rozycki" <macro@...ux-mips.org>
Subject: Re: [APIC] Kernel panic, rsync corruption, intel q8200, 2.6.28-rc8

Len Brown wrote:
>>> Do you have a second computer around with a serial port ? If yes, then
>>> please add the following to the kernel command line:
>>>
>>>        earlyprintk=serial,ttyS0,115200 apic=debug
>>>
>>> and connect the serial ports with a null modem cable. Fire up a
>>> terminal program on the second machine and capture the output.
>> I do have a second computer, and went out and bought a null modem adapter for
>> my serial cable and connected the two machines.  I've tried installing minicom
>> and also connecting it to ttyS0 at 115200 baud on the second machine, but when
>> I boot the first machine I don't see any output on the terminal.
> 
> /boot/grub/menu.lst:
> 
> serial --unit=0 --speed=115200 --word=8 --parity=no --stop=1
> terminal --timeout=300 serial console
> 
> is what I use.
> 
> this will give you a prompt from grub even before the kernel boots
> so you can select (and edit) your kernel via menu over the serial line
> if you wish.

I've got that working now.  I used minicom on the remote machine, 
capturing the output.  You can see me fumbling around, editing the 
kernel command and booting here:

http://intertwingly.net/stories/2009/02/09/minicom.out

While it is difficult to make out what I did given line wrapping, etc, 
what I started with was:

/boot/vmlinuz-2.6.27-11-generic 
root=UUID=4fce230e-fe72-4685-aab0-294ef1c20efa ro noapic quiet splash

After editing, what I had was

/boot/vmlinuz-2.6.27-11-generic 
root=UUID=4fce230e-fe72-4685-aab0-294ef1c20efa ro quiet splash 
earlyprintk=serial,ttyS0,115200 apic=debug

As you can see, the last line I saw was "Starting up ...", after which 
point the "MP-BIOS bug: 8254 timer not connected to IO-APIC" etc output 
appeared on the monitor that is directly connected to the machine being 
booted (i.e., this text did not appear on the minicom session).

> If this doesn't work, then the kernel earlyprintk is unlikely to work 
> also.

At the moment, it looks like it works, but earlyprintk does not work for 
me, at least not on Ubuntu 8.10, kernel 2.6.27-11-generic.

> Note that there may be some BIOS SETUP options related to the serial port 
> -- worth checking.
> 
> Also, in minicom, be sure to turn off HW flow control
> 
> there is a fancy serial console document someplace on this,
> probably at http://tldp.org/

As I have managed to get grub to talk to the serial console, I did not 
explore these options further.  Please let me know if there is something 
in particular I should explore.

> good luck,
> -Len

- Sam Ruby
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