From owner-freebsd-fs@FreeBSD.ORG Tue Oct 16 16:29:42 2012 Return-Path: Delivered-To: freebsd-fs@FreeBSD.org Received: from mx1.freebsd.org (mx1.freebsd.org [69.147.83.52]) by hub.freebsd.org (Postfix) with ESMTP id 76C93115; Tue, 16 Oct 2012 16:29:42 +0000 (UTC) (envelope-from avg@FreeBSD.org) Received: from citadel.icyb.net.ua (citadel.icyb.net.ua [212.40.38.140]) by mx1.freebsd.org (Postfix) with ESMTP id 8DC1F8FC14; Tue, 16 Oct 2012 16:29:40 +0000 (UTC) Received: from odyssey.starpoint.kiev.ua (alpha-e.starpoint.kiev.ua [212.40.38.101]) by citadel.icyb.net.ua (8.8.8p3/ICyb-2.3exp) with ESMTP id TAA25582; Tue, 16 Oct 2012 19:29:29 +0300 (EEST) (envelope-from avg@FreeBSD.org) Message-ID: <507D8B69.3090903@FreeBSD.org> Date: Tue, 16 Oct 2012 19:29:29 +0300 From: Andriy Gapon User-Agent: Mozilla/5.0 (X11; FreeBSD amd64; rv:16.0) Gecko/20121012 Thunderbird/16.0.1 MIME-Version: 1.0 To: dg17@penx.com Subject: Re: I have a DDB session open to a crashed ZFS server References: <1350317019.71982.50.camel@btw.pki2.com> <201210160844.41042.jhb@freebsd.org> <1350400597.72003.32.camel@btw.pki2.com> <201210161215.33369.jhb@freebsd.org> In-Reply-To: <201210161215.33369.jhb@freebsd.org> X-Enigmail-Version: 1.4.5 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Cc: freebsd-fs@FreeBSD.org X-BeenThere: freebsd-fs@freebsd.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: Filesystems List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 16 Oct 2012 16:29:42 -0000 on 16/10/2012 19:15 John Baldwin said the following: > On Tuesday, October 16, 2012 11:16:37 am Dennis Glatting wrote: >> On Tue, 2012-10-16 at 08:44 -0400, John Baldwin wrote: >>> On Monday, October 15, 2012 12:03:39 pm Dennis Glatting wrote: >>>> FreeBSD/amd64 (mc) (ttyu0) >>>> >>>> login: NMI ... going to debugger >>>> [ thread pid 11 tid 100003 ] >>> >>> You got an NMI, not a crash. What happens if you just continue ('c' command) >>> from DDB? >>> >> >> I hit the NMI button because of the "crash," which is a misword, to get >> into DDB. > > Ah, I would suggest "hung" or "deadlocked" next time. It certainly seems like > a deadlock since all CPUs are idle. Some helpful commands here might be > 'show sleepchain' and 'show lockchain'. > > Pick a "stuck" process (like find) and run: > > 'show sleepchain ' > > In your case though it seems both 'find' and the various 'pbzip2' threads > are stuck on a condition variable, so there isn't an easy way to identify > an "owner" that is supposed to awaken these threads. It could be a case > of a missed wakeup perhaps, but you'll need to get someone more familiar > with ZFS to identify where these codes should be awakened normally. > I would also re-iterate a suggestion that I made to Nikolay ealrier: http://article.gmane.org/gmane.os.freebsd.devel.file-systems/15981 BTW, in that case it turned out to be a genuine deadlock in ZFS ARC handling of lowmem. procstat -kk -a is a great help for analyzing such situations. -- Andriy Gapon