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From: Robert Watson <rwatson@FreeBSD.org>
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Cc: FreeBSD Current <freebsd-current@freebsd.org>
Subject: Re: ipi_nmi_handler
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On Sat, 5 Nov 2005, Randy Bush wrote:

>> It seems that if you put STOP_NMI in your kernel config, you need SMP as
>> well.
>
> <sigh>
>
> is STOP_NMI so wonderful that i should turn on SMP and the apic device?

STOP_NMI makes inter-processor interrupts for the debugger (and a few 
other things) use non-maskable interrupts instead of maskable ones.  So it 
doesn't actually do anything if you don't have an SMP system, as there 
will be no inter-processor interrupts on a single-processor system.

The STOP_NMI option may have been turned on by default without realizing 
that it wasn't quite implemented right -- it should only affect SMP 
systems, not be limited to compiling on them.

Robert N M Watson