linux-kernel - Re: Sysrq+B doesn't work on my box

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Message-ID: <c4e36d110807311101h4fea377dsb4470c0935bbd419@mail.gmail.com>
Date:	Thu, 31 Jul 2008 20:01:12 +0200
From:	"Zdenek Kabelac" <zdenek.kabelac@...il.com>
To:	"Henrique de Moraes Holschuh" <hmh@....eng.br>
Cc:	"Linux Kernel Mailing List" <linux-kernel@...r.kernel.org>
Subject: Re: Sysrq+B doesn't work on my box

2008/7/31 Henrique de Moraes Holschuh <hmh@....eng.br>:
> On Thu, 31 Jul 2008, Zdenek Kabelac wrote:
>> I'd like to get resolved this problem - my T61 machine doesn't reboot
>> with SysRQ+B key.
>> And I never remember if it was ever rebooting.
>>
>> This is all I know so far and I've no idea where could be the problem.
>
> Well, many of the different ThinkPad BIOSes are really sensitive to the
> proper boot/reboot/shutdown sequence (whatever it is).  Otherwise, the thing
> gets stuck in SMBIOS limbo and hung.  For exeample, we had major issues with
> boxes that only shut down half-way and ended up draining the cells to
> critical levels, a few months ago.  I don't know what finally fixed THAT
> one, but it was ugly.
>
> Here is another example: you can't get the TCO watchdog to reboot all (any?)
> thinkpads properly on hardware.  In my T43, the TCO watchdog IS hooked to
> something, but the BIOS hates it to trip and the entire box goes to
> neverland when it fires...
>
> If sysrq+b uses a different reboot path than the normal reboot path, it is
> the first hint of what is missing...

I've spend some time with tracking this issue more - and I've discovered this:

SysRQ+B  doesn't work with right AltGr on my keyboard - but it does
work with the left Alt which I'm not normally using (It's somewhat
easier to use the right one)
Any idea why AltGR+SysRQ+b does not work on T61 ?

Blocking reboot goes through the arch/x86/kernel/reboot.c
native_machine_emergency_restart()  case BOOT_KBD:  (10 loop outb()
iteration)
and ends in case BOOT_TRIPLE:  int3 - there it stays forever - during
the press of poweroff button it even visits that sysrq __handler.

if the kernel is started with   init=/bin/sh  - boot works without
problems - so it looks like that disabling reboot capability is the
result of Fedora's  rc.sysinit process.
Yet I've no idea what that could be....

Zdenek
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