linux-kernel - Re: [PATCH], issue EOI to APIC prior to calling crash_kexec in die

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Date:	Wed, 6 Feb 2008 14:40:40 -0500
From:	Vivek Goyal <vgoyal@...hat.com>
To:	Neil Horman <nhorman@...driver.com>
Cc:	linux-kernel@...r.kernel.org, tglx@...utronix.de, mingo@...hat.com,
	hpa@...or.com, kexec@...ts.infradead.org
Subject: Re: [PATCH], issue EOI to APIC prior to calling crash_kexec in
	die_nmi path

On Wed, Feb 06, 2008 at 02:25:55PM -0500, Neil Horman wrote:
> Hey all-
> 	A hang on kdump was reported to me awhile back, only when systems died
> via nmi watchdog panic.  The hang wouldn't always be in the same place, but it
> would usually be somewhere down in purgatory.  In looking at the code, it
> occured to me that since, during an nmi interrupt, we won't be able to handle
> additional interrupts, that we won't be able to halt the other processors on a
> system like we try to do in machine_crash_shutdown.  As such, it appears that
> leaving the other cpus running exposes us to the risk that another processor
> will encounter an error and halt the system while we are trying to boot the
> kdump kernel, and that can result in a hang.  I wrote the attached patch to end
> the nmi interrupt prior to calling crash_kexec from within die_nmi, and testing
> here has proven successfull.
> 

Hi Neil,

Why wouldn't I be able to stop other cpus if I am inside an NMI handler? I
just need to send an NMI IPI to other cpus and they should be able to
receive and handle it?

Thanks
Vivek
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