linux-kernel - Re: [PATCH 4/9] ftrace: Add enable/disable ftrace

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Message-ID: <1322511307.2921.173.camel@twins>
Date:	Mon, 28 Nov 2011 21:15:07 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	Jiri Olsa <jolsa@...hat.com>, fweisbec@...il.com, mingo@...hat.com,
	paulus@...ba.org, acme@...stprotocols.net,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 4/9] ftrace: Add enable/disable ftrace_ops control
 interface

On Mon, 2011-11-28 at 15:12 -0500, Steven Rostedt wrote:
> Actually, from what I've been told, x86 seems to be the only arch that
> does crazy things with NMIs. Most the other archs do NMI when the system
> is dead. That is, there's no return to normal system processing once an
> NMI is hit. 

Sparc64 implements effective NMIs by playing games with their interrupt
priority levels. local_irq_disable() disable the lower 15 (0-14) levels
only, and their PMU interrupts at level 15.

That generates an effective NMI (interrupt not blocked by
local_irq_disable()).
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