Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S964848AbVLRMJ2 (ORCPT ); Sun, 18 Dec 2005 07:09:28 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932700AbVLRMJ1 (ORCPT ); Sun, 18 Dec 2005 07:09:27 -0500 Received: from pentafluge.infradead.org ([213.146.154.40]:12944 "EHLO pentafluge.infradead.org") by vger.kernel.org with ESMTP id S932697AbVLRMJ0 (ORCPT ); Sun, 18 Dec 2005 07:09:26 -0500 Subject: Re: [2.6 patch] i386: always use 4k/4k stacks From: Arjan van de Ven To: Stefan Rompf Cc: linux-kernel@vger.kernel.org In-Reply-To: <200512181304.38054.stefan@loplof.de> References: <200512181149.02009.stefan@loplof.de> <1134904884.9626.7.camel@laptopd505.fenrus.org> <200512181304.38054.stefan@loplof.de> Content-Type: text/plain Date: Sun, 18 Dec 2005 13:09:22 +0100 Message-Id: <1134907763.9626.11.camel@laptopd505.fenrus.org> Mime-Version: 1.0 X-Mailer: Evolution 2.2.3 (2.2.3-2.fc4) Content-Transfer-Encoding: 7bit X-Spam-Score: -2.8 (--) X-Spam-Report: SpamAssassin version 3.0.4 on pentafluge.infradead.org summary: Content analysis details: (-2.8 points, 5.0 required) pts rule name description ---- ---------------------- -------------------------------------------------- -2.8 ALL_TRUSTED Did not pass through any untrusted hosts X-SRS-Rewrite: SMTP reverse-path rewritten from by pentafluge.infradead.org See http://www.infradead.org/rpr.html Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1556 Lines: 39 On Sun, 2005-12-18 at 13:04 +0100, Stefan Rompf wrote: > Am Sonntag 18 Dezember 2005 12:21 schrieb Arjan van de Ven: > > > the kernel has a stack overflow detector, which checks at irq entry time > > if the stack is "rather high" (7kb into the stack on a 8kb stack, 3.5kb > > on a 4k stack). When this warning hits there's still runway left (like > > 12.5 percent), but lets say the end becomes in sight. If the stack usage > > would be really tight, this "early warning" detector would be hitting a > > lot of people, right? > > Wrong. The probability that an interrupt happens just during the codepath with > highest stack usage is very small so it samples over 1000 times per second, more when busy. Multiplied over a very large number of users, and 2 years of time. "very small"... I don't quite agree there. > Anyway CONFIG_DEBUG_STACKOVERFLOW is not > enabled in 2.6.14.4 i386 defconfig. Don't know about vendor kernel kernels > though. the RH/Fedora ones have this enabled > > (and the "safety net" is a bit of misnomer, since it's not really safe, > > just "statistically different" if the shit hits the fan) > > If you can't even guarantee that 8k (or 6k) is enough, how can you vote for 4k > then ;-) it's not 4k it is 4k+4k btw. And my argument is that it's not less safe.. nor unsafe - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/