From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Fri, 25 May 2001 04:40:39 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Fri, 25 May 2001 04:40:31 -0400 Received: from ns.suse.de ([213.95.15.193]:4100 "HELO Cantor.suse.de") by vger.kernel.org with SMTP id ; Fri, 25 May 2001 04:40:23 -0400 Date: Fri, 25 May 2001 10:39:21 +0200 From: Andi Kleen To: Keith Owens Cc: Andi Kleen , Andreas Dilger , linux-kernel@vger.kernel.org Subject: Re: [CHECKER] large stack variables (>=1K) in 2.4.4 and 2.4.4-ac8 Message-ID: <20010525103921.A26630@gruyere.muc.suse.de> In-Reply-To: <20010525102015.C26038@gruyere.muc.suse.de> <26599.990779480@ocs3.ocs-net> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.2.5i In-Reply-To: <26599.990779480@ocs3.ocs-net>; from kaos@ocs.com.au on Fri, May 25, 2001 at 06:31:20PM +1000 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Fri, May 25, 2001 at 06:31:20PM +1000, Keith Owens wrote: > That is exactly what I said above, a separate fault task with its own > stack for every cpu. But there is no point in doing this to detect a > hardware stack overflow when the overflow has already corrupted the > struct task which is at the bottom of the stack segment. You can at least get a backtrace, which is useful enough. > > To get any benefit from hardware detection of kernel stack overflow you > must also dedicate the stack segment to hold only stack data. That > means moving struct task to yet another page, adding an extra page per > task. It is just too expensive, we write better code than that. Ah this was a misunderstanding. I was just talking about plain recovery from stack faults; not from hardware stack overflow detection. Even without wather tight overflow detection they happen often enough and usually not too long after a stack page overflow. -Andi