From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754573AbYH0HoZ (ORCPT ); Wed, 27 Aug 2008 03:44:25 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752762AbYH0HoR (ORCPT ); Wed, 27 Aug 2008 03:44:17 -0400 Received: from pasmtpb.tele.dk ([80.160.77.98]:37782 "EHLO pasmtpB.tele.dk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752414AbYH0HoQ (ORCPT ); Wed, 27 Aug 2008 03:44:16 -0400 X-Greylist: delayed 1491 seconds by postgrey-1.27 at vger.kernel.org; Wed, 27 Aug 2008 03:44:16 EDT Date: Wed, 27 Aug 2008 09:19:22 +0200 From: Jens Axboe To: Jeremy Fitzhardinge Cc: Linus Torvalds , linux-kernel@vger.kernel.org Subject: Re: [GIT PULL] block bits Message-ID: <20080827071921.GY20055@kernel.dk> References: <20080826070640.GR20055@kernel.dk> <20080826185636.GP20055@kernel.dk> <20080826191031.GQ20055@kernel.dk> <48B471B4.9030202@goop.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <48B471B4.9030202@goop.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Aug 26 2008, Jeremy Fitzhardinge wrote: > Jens Axboe wrote: > > On Tue, Aug 26 2008, Linus Torvalds wrote: > > > >> On Tue, 26 Aug 2008, Jens Axboe wrote: > >> > >>> I'll move those 1-2 patches to the 2.6.28 branch and resubmit the rest > >>> for you. > >>> > >> You will *delete* the absolute crap locking patch, that has no way of > >> being even 2.6.28 material. > >> > > > > Yeah, I thought that was obvious, I'll bounce it back to the Xen folks. > > > > Which, what? Was there an objection to one of the blkfront patches? (I > don't remember anything locking related in there anyway.) I see Linus' initial reply didn't make it to the list, not sure why. This is what he said: "it's so _incredibly_ broken that I refuse to pull any of the rest either, because the queue is obviously utter crap. In fact, even the "explanation" for that one is shit: "It shouldn't matter if an interrupt comes in whilst blkif_io_lock is held, as it will block on the lock [...]" where "as it will block" is apparently shorthand for "as it will deadlock and kill the machine"." This is the patch in question: http://git.kernel.dk/?p=linux-2.6-block.git;a=commitdiff;h=b58e9034c5e2424723948a63712eaf1332a76ab8;hp=5814f8d589a1daef3b1a6f3731fd65a858dc8466 and it doesn indeed look like crap. It DOES matter if an interrupt comes in on the local CPU while you are holding the blkif_io_lock, you'd be dead on the spot spinning forever in the irq handler. -- Jens Axboe