On Wed, 18 Jul 2001 20:47:32 +0200,
Ragnar Kj rstad <xfs@xxxxxxxxxxxxxxxxxxx> wrote:
>On Wed, Jul 18, 2001 at 01:38:31PM -0500, Eric Sandeen wrote:
>> $ echo 1 > /proc/sys/kernel/kdb
>We did.
>My comment was unclear - kdb work except when the lockup occurs.
Probable cause: disabled spin loop. When that occurs, all interrupt
handling is is dead, including the keyboard. You have to use a non
maskable interrupt (NMI) source to break into disabled spin loops. If
your box has an NMI button, use that button. Alas NMI buttons are very
rare, mainly hobby boxes using a hacked PCI card. Without an external
NMI source, use the software kernel NMI watchdog.
Compile your kernel for one of these combinations:
CONFIG_SMP=y
CONFIG_SMP=n && CONFIG_X86_IO_APIC=y && CONFIG_UP_NMI_WATCHDOG=y
All those options are on the processer menu. Boot the new kernel,
cat /proc/interrupts must show the NMI counter increasing. When the
machine hangs the NMI watchdog should kick in after 5 seconds.
You still need echo 1 > /proc/sys/kernel/kdb, for both hardware and
software NMI. Booting with kdb=on is even better. When the NMI is
raised, it will drop into kdb.
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