linux-kernel - Re: [PATCH][RFC] 4K stacks default, not a debug thing any more...?

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Message-ID: <20070719013725.GP11115@waste.org>
Date:	Wed, 18 Jul 2007 20:37:25 -0500
From:	Matt Mackall <mpm@...enic.com>
To:	Andrea Arcangeli <andrea@...e.de>
Cc:	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Rene Herman <rene.herman@...il.com>,
	Ray Lee <ray-lk@...rabbit.org>, Bodo Eggert <7eggert@....de>,
	Jeremy Fitzhardinge <jeremy@...p.org>,
	Jesper Juhl <jesper.juhl@...il.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	William Lee Irwin III <wli@...omorphy.com>,
	David Chinner <dgc@....com>,
	Arjan van de Ven <arjan@...radead.org>
Subject: Re: [PATCH][RFC] 4K stacks default, not a debug thing any more...?

On Thu, Jul 19, 2007 at 03:33:58AM +0200, Andrea Arcangeli wrote:
> On Thu, Jul 19, 2007 at 01:39:55AM +0100, Alan Cox wrote:
> > > About 4k stacks I was generally against them, much better to fail in
> > > fork than to risk corruption. The per-irq stack part is great feature
> > > instead (too bad it wasn't enabled for the safer 8k stacks).
> > 
> > 8K stacks without IRQ stacks are not "safer" so I don't understand your
> > comment ?
> 
> Ouch, see the reports about 4k stack crashes. I agree they're not
> safe w/o irq stacks (like on x86-64), but they're generally safer.

Here's a way to make forward progress on this whole thing:

Turn on irqstacks when using 8k stacks
Detect when usage with 8k stacks would overrun a 4k stack when doing
 our stack switch and do a WARN_ONCE
Fix up the damn bugs

-- 
Mathematics is the supreme nostalgia of our time.
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