PATCH/RFC: [kdump] fix APIC shutdown sequence
martin.wilck at fujitsu-siemens.com
Wed Aug 8 14:07:13 EDT 2007
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:
> <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
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