Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751971Ab1DOEW6 (ORCPT ); Fri, 15 Apr 2011 00:22:58 -0400 Received: from bombadil.infradead.org ([18.85.46.34]:38391 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751347Ab1DOEW5 (ORCPT ); Fri, 15 Apr 2011 00:22:57 -0400 Date: Fri, 15 Apr 2011 00:22:55 -0400 From: Christoph Hellwig To: Linus Torvalds Cc: Michael Guntsche , "linux-kernel@vger.kernel.org" , Jens Axboe Subject: Re: 2.6.39 Block layer regression was [Bug] Boot hangs with 2.6.39-rc[123]] Message-ID: <20110415042255.GC27928@infradead.org> References: <20110415035451@it-loops.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org See http://www.infradead.org/rpr.html Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1268 Lines: 26 On Thu, Apr 14, 2011 at 08:25:33PM -0700, Linus Torvalds wrote: > What's the thinking there? It looks very confused to me. It is. I sent a patch a couple of days ago to fix it. > Now, clearly RAID seems to be involved in the problem? The main thing > with that would be that the execution of the requests would tend to > generate new requests, that go back on the plug queue. Yes? And the > loop in flush_plug_list() means that they all should get flushed out, > I assume. But something clearly isn't working, and it does seem to be > about the RAID kind of setup. So either they didn't get put on the > plug queue, or the task got a new plug (which _wasn't_ flushed). > > Because we're clearly waiting for some request that hasn't completed. > Where in the plug queues would it be hiding? There's a thread where Neil explains what the problem with MD is - it needs a callback on unplug time to generate e.g. the write intent bitmap or as large as possible writes for RAID5. Jens and Neil have been looking into it. -- 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/