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From: ebiederm@xmission.com (Eric W. Biederman)
To: Neil Horman <nhorman@tuxdriver.com>
Cc: Vivek Goyal <vgoyal@redhat.com>,
	kexec@lists.infradead.org, linux-kernel@vger.kernel.org,
	mingo@redhat.com, "H. Peter Anvin" <hpa@zytor.com>,
	Ingo Molnar <mingo@elte.hu>,
	tglx@linutronix.de
Subject: Re: [PATCH], issue EOI to APIC prior to calling crash_kexec in die_nmi path
Date: Fri, 15 Feb 2008 07:02:28 -0700	[thread overview]
Message-ID: <m1lk5m9v2j.fsf@ebiederm.dsl.xmission.com> (raw)
In-Reply-To: <20080212210816.GA1862@hmsreliant.think-freely.org> (Neil Horman's message of "Tue, 12 Feb 2008 16:08:16 -0500")

Neil Horman <nhorman@tuxdriver.com> writes:

>> 
>> Neil, is it possible to do some serial console debugging to find out
>> where exactly we are hanging? Beats me, what's that operation which can
>> not be executed while being in NMI handler and makes system to hang. I am
>> also curious to know if it is nested NMI case.
>> 
>> Thanks
>> Vivek
>> 
>
>
> Hey-
> 	Some intermediate results:
>
> I've instrumented head.S in the kernel with the following code:
> #define SEROUT(z) \     
> mov $0x3F8,%dx;\
> movb z,%al;\
> outb %dx
>
>
> And peppered different ascii characters throughout the startup code from
> startup_32 to right before the jump to start_kernel.  When I panic the system
> via an:
> echo c > /proc/sysrq_trigger
> I see an appropriate sequence of characters on the serial console
>
> When I panic the box by forcing an NMI watchdog timeout however, I see nothing.
>  The machine will either hang, or reset into the bios.  I think this is
> reasonably conclusive in its indication that we're not getting into the second
> kernel when this problem occurs.  Next I'll instrument the purgatory code in a
> simmilar way.

My apologies for the late reply.  You should be able to use the --console-serial
option to kexec to get output from purgatory, which will catch everything
except a little bit of the assembly stub.  purgatory even has a stripped down
version of printf you can call.

Eric

  reply	other threads:[~2008-02-15 14:07 UTC|newest]

Thread overview: 25+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-02-06 19:25 Neil Horman
2008-02-06 19:40 ` Vivek Goyal
2008-02-06 20:12   ` Neil Horman
2008-02-06 20:21     ` H. Peter Anvin
2008-02-06 21:04       ` Neil Horman
2008-02-06 20:35     ` Vivek Goyal
2008-02-06 22:00 ` Ingo Molnar
2008-02-06 22:48   ` Vivek Goyal
2008-02-06 22:53     ` Ingo Molnar
2008-02-06 22:56     ` H. Peter Anvin
2008-02-06 23:36       ` Ingo Molnar
2008-02-06 23:50         ` Vivek Goyal
2008-02-07  0:31         ` Eric W. Biederman
2008-02-07  0:39           ` Ingo Molnar
2008-02-07  1:30             ` Eric W. Biederman
2008-02-07 12:17           ` Neil Horman
2008-02-07 12:24             ` Ingo Molnar
2008-02-07 20:37               ` Neil Horman
2008-02-08 16:14               ` Neil Horman
2008-02-08 16:45                 ` Vivek Goyal
2008-02-08 17:26                   ` Neil Horman
2008-02-12 21:08                   ` Neil Horman
2008-02-15 14:02                     ` Eric W. Biederman [this message]
2008-02-20 14:57                     ` Neil Horman
2008-02-08 16:54               ` Andi Kleen

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