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

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Date:	Thu, 31 Jul 2008 15:45:24 +0200
From:	"Zdenek Kabelac" <zdenek.kabelac@...il.com>
To:	"Linux Kernel Mailing List" <linux-kernel@...r.kernel.org>
Subject: Sysrq+B doesn't work on my box

Hi

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.

System is running Fedora rawhide 64bit.

If I press any other  SysRQ combination - it works - so things like
Sync, Umount, powerOff do work normally.
It's just Boot  which does not even get to the  __handle  routine
(I've added one extra simple debug prinkt
for this case)

So - who/how/where could mask this key sequence from being delivered
to the sysrq driver?
(obviously I do not have any problems typing letter 'b' itself)

Another issue is - that even with  'echo b >/proc/sysrq-triggers' my
machine doesn't reboot.
It just goes though the native_machine_emergency_restart  BOOT_KBD &
BOOT_TRIPLE cases
(as I can see via another debug prints) and no reboot actually happens -
what kind of routines should trigger the reboot ?
At this moment I had to power-off machine manually holding power switch for 4s.

(using regular command 'reboot' restarts the machine without a single problem)

To make more mysterious - I know couple other T61 users - which do not
have any problems
with SysRq+B - and when I even use their kernels - I've no success with reboot.

As the machine works just fine otherwise I could hardly imagine there
could be a hw bug just cause some reboot lock???

Thanks for any hint

Zdenek

Attached my configuration

Download attachment "config" of type "application/octet-stream" (63786 bytes)