Re: non-maskable interrupt?

[John Levon <moz@compsoc.man.ac.uk>]

On Thu, 22 Feb 2001, Michael B. Rash wrote:

> 
> Is it possible for a NIC card to generate a non-maskable interrupt, say if
> it were malfunctioning?

If you mean technically possible, then yes. If you mean actually happens, then I
don't know ...

> On a general note, does the kernel define interrupt handling routines for
> non-maskable interrupts, or is this not possible?  From what I have read,
> it seems that non-maskable interrupts are generated when something
> exceptionally bad happens such as an unrecoverable memory error.  Does
> this imply that the system can only crash when such an interrupt is
> generated or are there circumstances in which a non-maskable interrupt can
> be handled and the system continue to function (even if it is in some
> limited state)?

This is ONE of the uses for NMIs. They are also used for example on a MCA architecture,
and can be of great use when profiling.

There's nothing inherently instable about receiving an NMI, it is just that
some errors are delivered as NMI interrupts.

You can look at the nmi handling code in arch/i386/kernel/, the function do_nmi()

john

-- 
"That government is best which governs least."
	- Henry David Thoreau 

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