linux-kernel - Re: [PATCH] x86 NMI: Be smarter about invoking panic() inside NMI handler.

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Message-ID: <CANz0V+7J=gN1_cH2jCnCSdQ=TnL9=2+S+6orBPPep=-tFN4p0A@mail.gmail.com>
Date:	Thu, 29 Mar 2012 03:19:56 -0400
From:	"Andrei E. Warkentin" <andrey.warkentin@...il.com>
To:	Don Zickus <dzickus@...hat.com>
Cc:	linux-kernel@...r.kernel.org, kgdb-bugreport@...ts.sourceforge.net,
	jason.wessel@...driver.com
Subject: Re: [PATCH] x86 NMI: Be smarter about invoking panic() inside NMI handler.

Hi Don,

Thank you for your feedback!

2012/3/27 Don Zickus <dzickus@...hat.com>:
>
> Hmm, if try_panic fails, then the cpu continues on executing code.  This
> might further corrupt an already broken system.  So I don't think this
> patch will work as is.
>

I see what you are saying. I could make the argument that this kind
of system corruption could occur anyway even if you did panic inside
an IRQ context instead, but I would tend to agree that your proposed
solution is much better than adding another panic interface.

> Perhaps instead of panic'ing in the NMI context, we use irq_work and panic
> in an interrupt context instead.  We still get the system to stop (though
> it might still execute some interrupts) and it will be out of the NMI
> context.
>
> However, you will still run into a similar problem when in the
> panic/reboot case we shutdown all the remote cpus and have them sitting in
> a similar cpu_relax loop in the NMI context, while the panic'ing cpu
> cleans things up.
>

Sorry, could you clarify what you mean? How does this affect KDB usage?

A
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