To: Ingo Molnar <mingo@elte.hu>
Cc: linux-kernel@vger.kernel.org, Matt Mackall <mpm@selenic.com>,
       Andrew Morton <akpm@osdl.org>
Subject: Re: [PATCH 7/15] misc: Make x86 doublefault handling optional
References: <8.282480653@selenic.com> <200511160713.07632.rob@landley.net>
	<20051116182145.GP31287@waste.org>
	<f1079b100511161121g1997cfb4jc8e8aec5072c1d92@mail.gmail.com>
	<20051212103611.GA6416@elte.hu>
From: Andi Kleen <ak@suse.de>
Date: 12 Dec 2005 09:22:42 -0700
In-Reply-To: <20051212103611.GA6416@elte.hu>
Message-ID: <p73u0denv3h.fsf@verdi.suse.de>
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Ingo Molnar <mingo@elte.hu> writes:
> 
> in the past couple of years i saw double-faults at a rate of perhaps 
> once a year - and i frequently hack lowlevel glue code! So the 
> usefulness of this code in the field, and especially on an embedded 
> platforms, is extremely limited.

If it only saves an hour or developer time on some bug report
it has already justified its value.

Also to really save memory there are much better areas
of attack than this relatively slim code.

> in fact, i've experienced triple-faults (== spontaneous reboots) to be 
> at least 10 times more frequent than double-faults! I.e. _if_ your 
> kernel (or hardware) is screwed up to the degree that it would 
> double-fault, it will much more likely also triple-fault.

A common case where this doesn't hold is breaking the [er]sp 
in kernel code.

-Andi (who sees double faults more often) 
-
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