From owner-freebsd-hackers@FreeBSD.ORG Mon Feb 9 14:23:26 2015 Return-Path: Delivered-To: freebsd-hackers@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by hub.freebsd.org (Postfix) with ESMTPS id D550728E for ; Mon, 9 Feb 2015 14:23:26 +0000 (UTC) Received: from mail.myota.org (mail.myota.org [85.10.206.105]) by mx1.freebsd.org (Postfix) with ESMTP id 65602930 for ; Mon, 9 Feb 2015 14:23:25 +0000 (UTC) Received: from mobile.client (187stb36.codetel.net.do [64.32.117.187]) (authenticated bits=128) by mail.myota.org (8.14.9/8.14.9) with ESMTP id t19EN0hv009227; Mon, 9 Feb 2015 15:23:08 +0100 (CET) (envelope-from andre@fbsd.ata.myota.org) Received: from submit.client ([127.0.0.1]) by schlappy.local (8.14.9/8.14.9) with ESMTP id t19EMgWC008768; Mon, 9 Feb 2015 15:22:43 +0100 (CET) (envelope-from andre@fbsd.ata.myota.org) Received: (from user@localhost) by schlappy.local (8.14.9/8.14.9/Submit) id t19EMgPR008767; Mon, 9 Feb 2015 15:22:42 +0100 (CET) (envelope-from andre@fbsd.ata.myota.org) Date: Mon, 9 Feb 2015 15:22:42 +0100 From: Andre Albsmeier To: freebsd-hackers@freebsd.org Subject: [unionfs] deadlocking a 9-STABLE machine with two unionfs mounts onto the same mountpoint Message-ID: <20150209142242.GA8734@schlappy> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline X-Echelon: V, RSA, Telex, Sears, SWAT X-Advice: Drop that crappy M$-Outlook, I'm tired of your viruses! User-Agent: Mutt/1.5.21 (2010-09-15) X-Greylist: Not delayed on 85.10.206.105, ACL: AUTH(59), Origin: DO, OS: FreeBSD 9.x or newer X-Virus-Scanned: clamav-milter 0.98.6 at colo X-Virus-Status: Clean Cc: andre@fbsd.ata.myota.org X-BeenThere: freebsd-hackers@freebsd.org X-Mailman-Version: 2.1.18-1 Precedence: list List-Id: Technical Discussions relating to FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 09 Feb 2015 14:23:26 -0000 Retrying here as -fs didn't show up any results... ----- Forwarded message ----- I can reliably deadlock a 9.3-STABLE by the following procedure: Let's assume that /tmp is a standard swap-backed file system already. First let's set up what we need: mkdir /tmp/1 /tmp/2 mount -v -t unionfs /tmp/1 /usr/local mount -v -t unionfs /tmp/2 /usr/local No let's lock the system: mkdir /tmp/2/bla while :; do echo go tar -cC /usr/src/etc -f - . | tar -xpC /tmp/2/bla -f - done It survives about 3 or 4 rounds, sometimes more, sometimes only 2. It is important to use tar to copy the stuff. If we replace the tar line by e.g. cp -pR /usr/src/etc/* /tmp/2/bla things are all well. The system doesn't lock up entirely, you can move the mouse and ping it but no fs access is possible anymore. One can switch to the console and enter the debugger but a reboot with ctrl-alt-del doesn't work... The interesting part is that all this worked pretty well on 9-STABLE until approx. 2 months ago. But nothing had been committed to unionfs for a long time so I really have no idea what's going on. It also reminds us of https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=161511 but this stuff had been merged to 9-STABLE already... Anything I can do to get this fixed? ----- End forwarded message -----