Re: [PATCH 4/9] ftrace: Add enable/disable ftrace_ops controlinterface

From: Peter Zijlstra
Date: Mon Nov 28 2011 - 15:15:23 EST


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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