From mboxrd@z Thu Jan 1 00:00:00 1970 From: Alex Elder Subject: Re: rbd map command hangs for 15 minutes during system start up Date: Wed, 19 Dec 2012 15:25:56 -0600 Message-ID: <50D230E4.6060805@inktank.com> References: <50B7C788.6040404@inktank.com> <50B93FCA.2060801@inktank.com> <50BC2DE6.6050307@inktank.com> <50C65AE5.2050704@inktank.com> <50C774FD.9030107@inktank.com> <50C78D09.5050403@inktank.com> <50CB57E2.10703@inktank.com> <50CB69E5.7080001@ink tank.com> <50D0951F.6050106@inktank.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: Received: from mail-ie0-f177.google.com ([209.85.223.177]:62681 "EHLO mail-ie0-f177.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751009Ab2LSVZ7 (ORCPT ); Wed, 19 Dec 2012 16:25:59 -0500 Received: by mail-ie0-f177.google.com with SMTP id k13so3503123iea.8 for ; Wed, 19 Dec 2012 13:25:58 -0800 (PST) In-Reply-To: Sender: ceph-devel-owner@vger.kernel.org List-ID: To: Nick Bartos Cc: Sage Weil , Gregory Farnum , Josh Durgin , Mandell Degerness , "ceph-devel@vger.kernel.org" On 12/18/2012 12:05 PM, Nick Bartos wrote: > I've added the output of "ps -ef" in addition to triggering a trace > when a hang is detected. Not much is generally running at that point, > but you can have a look: > > https://gist.github.com/raw/4330223/2f131ee312ee43cb3d8c307a9bf2f454a7edfe57/rbd-hang-1355851498.txt This helped a lot. I updated the bug with a little more info. http://tracker.newdream.net/issues/3519 I also think I have now found something that could explain what you are seeing, and am developing a fix. I'll provide you an update as soon as I have tested what I come up with, almost certainly this afternoon. -Alex > Is it possible that there is some sort of deadlock going on? We are > doing the rbd maps (and subsequent filesystem mounts) on the same > systems which are running the ceph-osd and ceph-mon processes. To get > around the 'sync' deadlock problem, we are using a patch from Sage > which ignores system wide sync's on filesystems mounted with the > 'mand' option (and we mount the underlying osd filesystems with > 'mand'). However I am wondering if there is potential for other types > of deadlocks in this environment. > > Also, we recently saw an rbd hang in a much older version, running > kernel 3.5.3 with only the sync hack patch, along side ceph 0.48.1. > It's possible that this issue was around for some time, just the > recent patches made it happen more often (and thus more reproducible) > for us. > > > On Tue, Dec 18, 2012 at 8:09 AM, Alex Elder wrote: >> On 12/17/2012 11:12 AM, Nick Bartos wrote: >>> Here's a log with the rbd debugging enabled: >>> >>> https://gist.github.com/raw/4319962/d9690fd92c169198efc5eecabf275ef1808929d2/rbd-hang-test-1355763470.log >>> >>> On Fri, Dec 14, 2012 at 10:03 AM, Alex Elder wrote: >>>> On 12/14/2012 10:53 AM, Nick Bartos wrote: >>>>> Yes I was only enabling debugging for libceph. I'm adding debugging >>>>> for rbd as well. I'll do a repro later today when a test cluster >>>>> opens up. >>>> >>>> Excellent, thank you. -Alex >> >> I looked through these debugging messages. Looking only at the >> rbd debugging, what I see seems to indicate that rbd is idle at >> the point the "hang" seems to start. This suggests that the hang >> is not due to rbd itself, but rather whatever it is that might >> be responsible for using the rbd image once it has been mapped. >> >> Is that possible? I don't know what process you have that is >> mapping the rbd image, and what is supposed to be the next thing >> it does. (I realize this may not make a lot of sense, given >> a patch in rdb seems to have caused the hang to begin occurring.) >> >> Also note that the debugging information available (i.e., the >> lines in the code that can output debugging information) may >> well be incomplete. So if you don't find anything it may be >> necessary to provide you with another update which might include >> more debugging. >> >> Anyway, could you provide a little more context about what >> is going on sort of *around* rbd when activity seems to stop? >> >> Thanks a lot. >> >> -Alex