lkml.org 
[lkml]   [2007]   [Aug]   [8]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: PATCH/RFC: [kdump] fix APIC shutdown sequence
Vivek Goyal wrote:

> Got this oops while testing your patch when I did
> "echo c > /proc/sysrq-trigger"

That's bad :-(

...
> Unable to handle kernel NULL pointer dereference at 0000000000000000 RIP:
[<0000000000000000>]
> <IRQ> [<ffffffff8025afd0>] handle_edge_irq+0x5c/0x127
> [<ffffffff8020e1ae>] do_IRQ+0xf1/0x15f
> [<ffffffff8020c191>] ret_from_intr+0x0/0xa
> <EOI> <NMI> [<ffffffff80351ae3>] __delay+0x6/0x10
> [<ffffffff8021e328>] crash_nmi_callback+0x4b/0x77

Obviously, it the oops occurs after the IRQs are re-enabled in crash_nmi_callback().
It appears that desc->chip->mask (in mask_ack_irq(), kernel/irq/chip.c:462) was NULL.
I have no idea how my patch could cause that.

This proves that re-enabling IRQs in this situation is too dangerous :-(.
I really did hundreds of dumps in different ways (echo c>/proc/sysrq-trigger,
forcing Oops and panic(), actually hititng Alt-Sysrq) and this never happened to
me.

Martin

--
Martin Wilck
PRIMERGY System Software Engineer
FSC IP ESP DE6

Fujitsu Siemens Computers GmbH
Heinz-Nixdorf-Ring 1
33106 Paderborn
Germany

Tel: ++49 5251 8 15113
Fax: ++49 5251 8 20409
Email: mailto:martin.wilck@fujitsu-siemens.com
Internet: http://www.fujitsu-siemens.com
Company Details: http://www.fujitsu-siemens.com/imprint.html
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2007-08-08 20:09    [W:3.750 / U:0.092 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site