From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965107Ab2CFTC3 (ORCPT ); Tue, 6 Mar 2012 14:02:29 -0500 Received: from mx1.redhat.com ([209.132.183.28]:2011 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756346Ab2CFTC2 (ORCPT ); Tue, 6 Mar 2012 14:02:28 -0500 Date: Tue, 6 Mar 2012 14:02:11 -0500 From: Vivek Goyal To: Tejun Heo Cc: axboe@kernel.dk, ctalbott@google.com, rni@google.com, linux-kernel@vger.kernel.org, dm-devel@redhat.com Subject: Re: [PATCHSET] blkcg: accumulated blkcg updates Message-ID: <20120306190211.GD32148@redhat.com> References: <1329875223-5102-1-git-send-email-tj@kernel.org> <20120305210726.GC1263@google.com> <20120305210836.GD1263@google.com> <20120306150709.GA32148@redhat.com> <20120306162455.GB32148@redhat.com> <20120306183942.GC32148@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20120306183942.GC32148@redhat.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Mar 06, 2012 at 01:39:42PM -0500, Vivek Goyal wrote: > On Tue, Mar 06, 2012 at 11:24:55AM -0500, Vivek Goyal wrote: > > On Tue, Mar 06, 2012 at 10:07:09AM -0500, Vivek Goyal wrote: > > > > [..] > > > > > > My system is hanging during reboot. Last message I see is "Detaching DM > > > devices" and nothing happens after that. I shall have to do some more > > > testing to figure out when did that start happening. > > > > Ok, git bisect shows that very first patch to drain the queue is culprit. > > > > 9e5b9f8 block: blk-throttle should be drained regardless of q->elevator > > > > Will do some more debugging. > > Hmm..., haven't reached to the bottom of the issue yet, but there is more > data. Ok, found it. Basically we have not initialized the q->queue_head during queue creation. Hence we end up thinking that q->queue_head is not empty. So following fixed the issue for me. I still don't understand the special cased code (q->queue_head is not empty but don't kick queue). block/blk-core.c | 1 + 1 file changed, 1 insertion(+) Index: tejun-misc/block/blk-core.c =================================================================== --- tejun-misc.orig/block/blk-core.c 2012-03-07 00:47:14.325852192 -0500 +++ tejun-misc/block/blk-core.c 2012-03-07 00:47:15.998853132 -0500 @@ -558,6 +558,7 @@ struct request_queue *blk_alloc_queue_no setup_timer(&q->timeout, blk_rq_timed_out_timer, (unsigned long) q); INIT_LIST_HEAD(&q->timeout_list); INIT_LIST_HEAD(&q->icq_list); + INIT_LIST_HEAD(&q->queue_head); #ifdef CONFIG_BLK_CGROUP INIT_LIST_HEAD(&q->blkg_list); #endif Thanks Vivek