From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759326AbZE2Msx (ORCPT ); Fri, 29 May 2009 08:48:53 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1758079AbZE2Msp (ORCPT ); Fri, 29 May 2009 08:48:45 -0400 Received: from atrey.karlin.mff.cuni.cz ([195.113.26.193]:51540 "EHLO atrey.karlin.mff.cuni.cz" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757931AbZE2Mso (ORCPT ); Fri, 29 May 2009 08:48:44 -0400 Date: Fri, 29 May 2009 12:34:32 +0200 From: Pavel Machek To: Andi Kleen Cc: Andrew Morton , paul@mad-scientist.net, linux-kernel@vger.kernel.org Subject: Re: [2.6.27.24] Kernel coredump to a pipe is failing Message-ID: <20090529103432.GA1397@ucw.cz> References: <1243355634.29250.331.camel@psmith-ubeta.netezza.com> <878wkjobbm.fsf@basil.nowhere.org> <20090526160017.98fc62e4.akpm@linux-foundation.org> <20090526231428.GK846@one.firstfloor.org> <20090526162821.02e11d5b.akpm@linux-foundation.org> <20090526234109.GL846@one.firstfloor.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20090526234109.GL846@one.firstfloor.org> User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed 2009-05-27 01:41:09, Andi Kleen wrote: > On Tue, May 26, 2009 at 04:28:21PM -0700, Andrew Morton wrote: > > On Wed, 27 May 2009 01:14:28 +0200 > > Andi Kleen wrote: > > > > > On Tue, May 26, 2009 at 04:00:17PM -0700, Andrew Morton wrote: > > > > dump_write() doesn't seem right, either. If ->write() returns, say, > > > > 100 then the dump should keep on going. At present it treats this > > > > return as an error. > > > > > > I think that's correct actually. Short write typically means serious > > > issue like disk full or broken pipe, so stopping is good. > > > > But we shouldn't assume that. It could be that the ->write > > implementation is perfectly able to absorb the remaining data. > > Maybe in theory, but in practice that's unlikely isn't it? > Disk is full or pipe is blocking etc. > > > We should only error out of the write() returned zero or -EFOO. > > The current code is simply buggy, but got lucky. > > Maybe very pedantically, but I would argue that most programs > don't do what you're saying (retry on any short write) and > it's actually not very nice to always write a loop for each write. > > Also any IO device who relies on that would likely find > that it won't work with a lot of software. > > So I think the current behaviour is ok, just need to get > rid of the signals. Short writes are normal at least for pipes and sockets... better fix the sw. -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html