linux-kernel - Re: RCU lockup in the SMP idle thread, help...

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Message-ID: <CACRpkdaOG59CNvqUGFer+1TcVM8ovJwxmc3ZryJKw--PJ=bzsQ@mail.gmail.com>
Date:	Thu, 20 Sep 2012 10:46:34 +0200
From:	Linus Walleij <linus.walleij@...aro.org>
To:	paulmck@...ux.vnet.ibm.com, Nicolas Pitre <nico@...aro.org>
Cc:	John Stultz <john.stultz@...aro.org>,
	Daniel Lezcano <daniel.lezcano@...aro.org>,
	linux-kernel@...r.kernel.org
Subject: Re: RCU lockup in the SMP idle thread, help...

On Thu, Sep 20, 2012 at 2:03 AM, Paul E. McKenney
<paulmck@...ux.vnet.ibm.com> wrote:

> Any thoughts on the feasibility of implementing NMI-based stack backtraces
> for ARM?

Nico's department, so let's page him.

In IIRC ux500 all NMIs are reserved for the secure world, so it's
basically a no can do. :-(

And I'm told this is the case in some other ARMv7 arches too.

> In the meantime, a crude fallback is for the CPU that detected the stall
> to trace the stack of the task running on the other CPU.  See below for
> a crude (and untested) patch.

I'll test!

Thanks,
Linus Walleij
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