To: Russell Miller <rmiller@duskglow.com>
Cc: Kurt Wall <kwall@kurtwerks.com>, linux-kernel@vger.kernel.org
Subject: Re: is killing zombies possible w/o a reboot?
References: <200411030751.39578.gene.heskett@verizon.net>
	<200411031901.28977.rmiller@duskglow.com>
	<87654m4clz.fsf@asmodeus.mcnaught.org>
	<200411031945.20894.rmiller@duskglow.com>
From: Doug McNaught <doug@mcnaught.org>
Date: Wed, 03 Nov 2004 20:56:28 -0500
In-Reply-To: <200411031945.20894.rmiller@duskglow.com> (Russell Miller's
 message of "Wed, 3 Nov 2004 20:45:20 -0500")
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Russell Miller <rmiller@duskglow.com> writes:

> Wouldn't it help with device driver problems?  Couldn't ring 1 be
> used to make sure an errant driver doesn't drop the kernel, at least
> on x86 machines?

As I understand it:

1) Ring transitions aren't free.
2) The API between drivers and kernel is always in flux; drivers
   expect to be able to access internal kernel data structures.
   Making drivers run in ring 1 on even one of the N architectures
   would be a major refactoring and would constrain API changes.
   Freezing the internal API is something the developers don't want to
   do.
3) There are probably plenty of ways for a buggy driver to crash the
   kernel even if it's running in ring 1 (turn off interrupts and
   leave them off, etc).

So the upshot is that it's probably not worth the work and portability
hassles.

-Doug
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