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Date: Tue, 9 Aug 2016 14:37:35 +0200
From: Petr Mladek <pmladek@suse.com>
To: Chris Metcalf <cmetcalf@mellanox.com>
Cc: Peter Zijlstra <peterz@infradead.org>,
        "Rafael J. Wysocki" <rjw@rjwysocki.net>,
        Russell King <linux@arm.linux.org.uk>,
        Thomas Gleixner <tglx@linutronix.de>,
        Aaron Tomlin <atomlin@redhat.com>, Ingo Molnar <mingo@redhat.com>,
        Andrew Morton <akpm@osdl.org>,
        Daniel Thompson <daniel.thompson@linaro.org>,
        linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v7 2/4] nmi_backtrace: do a local dump_stack() instead of
 a self-NMI
Message-ID: <20160809123735.GF13300@pathway.suse.cz>
References: <1470672218-16059-1-git-send-email-cmetcalf@mellanox.com>
 <1470672218-16059-3-git-send-email-cmetcalf@mellanox.com>
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On Mon 2016-08-08 12:03:36, 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@mellanox.com>
> Acked-by: Aaron Tomlin <atomlin@redhat.com>

Sounds and looks fine to me.

Reviewed-by: Petr Mladek <pmladek@suse.com>

Best Regards,
Petr Mladek