From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965018AbWDMXM2 (ORCPT ); Thu, 13 Apr 2006 19:12:28 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S965031AbWDMXMS (ORCPT ); Thu, 13 Apr 2006 19:12:18 -0400 Received: from smtp.osdl.org ([65.172.181.4]:49822 "EHLO smtp.osdl.org") by vger.kernel.org with ESMTP id S965018AbWDMXLo (ORCPT ); Thu, 13 Apr 2006 19:11:44 -0400 Date: Thu, 13 Apr 2006 16:11:30 -0700 (PDT) From: Linus Torvalds To: Alan Cox cc: Nick Piggin , Andrew Morton , Dan Bonachea , linux-kernel@vger.kernel.org Subject: Re: PROBLEM: pthread-safety bug in write(2) on Linux 2.6.x In-Reply-To: Message-ID: References: <6.2.5.6.2.20060412173852.033dbb90@cs.berkeley.edu> <20060412214613.404cf49f.akpm@osdl.org> <443DE2BD.1080103@yahoo.com.au> <1144965022.12387.23.camel@localhost.localdomain> <1144969549.12387.33.camel@localhost.localdomain> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 13 Apr 2006, Linus Torvalds wrote: > > > On Fri, 14 Apr 2006, Alan Cox wrote: > > > > Quality for whom ? There is a measurable cost to all that extra locking > > which will hurt everyone. Given existing kernels don't make the > > guarantee and SuS v3 does not make the guarantee the apps that need it > > will continue to do the extra work themselves anyway. > > True. Side note: if you want the strange POSIX guarantees that Dan quoted (atomicity between write and fstat), you'd almost have to do it with user-space crapola magic locks. Doing it in the kernel would just be insane, you'd have to have some per-process "IO semaphore". (Doing it in user space _also_ sounds insane, but then you could have a switch like "POSIX me harder, and do all the really stupid things" at compile time or something) Linus