linux-kernel - Re: [PATCH v5 2/4] nmi_backtrace: do a local dump

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Message-ID: <20160414151933.GF20425@atomlin.usersys.redhat.com>
Date:	Thu, 14 Apr 2016 16:19:33 +0100
From:	Aaron Tomlin <atomlin@...hat.com>
To:	Chris Metcalf <cmetcalf@...lanox.com>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Petr Mladek <pmladek@...e.com>,
	Russell King <linux@....linux.org.uk>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>, Andrew Morton <akpm@...l.org>,
	Daniel Thompson <daniel.thompson@...aro.org>,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 2/4] nmi_backtrace: do a local dump_stack() instead of
 a self-NMI

On Tue 2016-04-05 13:26 -0400, Chris Metcalf wrote:
> Currently on arm there is code that checks whether it should call
> dump_stack() explicitly, to avoid trying to raise an NMI when the
> current context is not preemptible by the backtrace IPI.  Similarly,
> the forthcoming arch/tile support uses an IPI mechanism that does
> not support generating an NMI to self.
> 
> Accordingly, move the code that guards this case into the generic
> mechanism, and invoke it unconditionally whenever we want a
> backtrace of the current cpu.  It seems plausible that in all cases,
> dump_stack() will generate better information than generating a
> stack from the NMI handler.  The register state will be missing,
> but that state is likely not particularly helpful in any case.
> 
> Or, if we think it is helpful, we should be capturing and emitting
> the current register state in all cases when regs == NULL is passed
> to nmi_cpu_backtrace().
> 
> Signed-off-by: Chris Metcalf <cmetcalf@...lanox.com>
> ---
>  arch/arm/kernel/smp.c | 9 ---------
>  lib/nmi_backtrace.c   | 9 +++++++++
>  2 files changed, 9 insertions(+), 9 deletions(-)

Thanks Chris.

Acked-by: Aaron Tomlin <atomlin@...hat.com>

-- 
Aaron Tomlin