From 8b1ffe9550e71224c43d8c754245bd76f4ea9bb8 Mon Sep 17 00:00:00 2001
From: Corey Minyard <minyard@acm.org>
Date: Mon, 8 May 2006 15:17:25 +0200
Subject: [PATCH] [PATCH] x86_64: add nmi_exit to die_nmi
Playing with NMI watchdog on x86_64, I discovered that it didn't
do what I expected. It always panic-ed, even when it didn't
happen from interrupt context. This patch solves that
problem for me. Also, in this case, do_exit() will be called
with interrupts disabled, I believe. Would it be wise to also
call local_irq_enable() after nmi_exit()?
[Yes I added it -AK]
Currently, on x86_64, any NMI watchdog timeout will cause a panic
because the irq count will always be set to be in an interrupt
when do_exit() is called from die_nmi(). If we add nmi_exit() to
the die_nmi() call (since the nmi will never exit "normally")
it seems to solve this problem. The following small program
can be used to trigger the NMI watchdog to reproduce this:
main ()
{
iopl(3);
for (;;) asm("cli");
}
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
---
arch/x86_64/kernel/traps.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/arch/x86_64/kernel/traps.c b/arch/x86_64/kernel/traps.c
index 0ebb281aa178..6b87268c5c2e 100644
--- a/arch/x86_64/kernel/traps.c
+++ b/arch/x86_64/kernel/traps.c
@@ -472,6 +472,8 @@ void __kprobes die_nmi(char *str, struct pt_regs *regs)
panic("nmi watchdog");
printk("console shuts up ...\n");
oops_end(flags);
+ nmi_exit();
+ local_irq_enable();
do_exit(SIGSEGV);
}