From owner-freebsd-stable@FreeBSD.ORG Wed Nov 16 15:04:10 2011 Return-Path: Delivered-To: freebsd-stable@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 6CBD2106564A; Wed, 16 Nov 2011 15:04:10 +0000 (UTC) (envelope-from joel@vnode.se) Received: from mail.vnode.se (mail.vnode.se [62.119.52.80]) by mx1.freebsd.org (Postfix) with ESMTP id 1F7348FC14; Wed, 16 Nov 2011 15:04:09 +0000 (UTC) Received: from mail.vnode.se (localhost [127.0.0.1]) by mail.vnode.se (Postfix) with ESMTP id 03B8BE3F07A; Wed, 16 Nov 2011 15:45:34 +0100 (CET) X-Virus-Scanned: amavisd-new at vnode.se Received: from mail.vnode.se ([127.0.0.1]) by mail.vnode.se (mail.vnode.se [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id kblE1TAV6jf2; Wed, 16 Nov 2011 15:45:28 +0100 (CET) Received: from goofy01.vnodelab.local (unknown [212.247.52.12]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by mail.vnode.se (Postfix) with ESMTPSA id 8C92DE3F079; Wed, 16 Nov 2011 15:45:28 +0100 (CET) Date: Wed, 16 Nov 2011 15:45:26 +0100 From: Joel Dahl To: Alexander Motin Message-ID: <20111116144526.GV83971@goofy01.vnodelab.local> References: <4EC392DA.2030302@FreeBSD.org> <4EC3C99C.8020203@FreeBSD.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4EC3C99C.8020203@FreeBSD.org> User-Agent: Mutt/1.5.21 (2010-09-15) Cc: "Bjoern A. Zeeb" , freebsd-stable@freebsd.org Subject: Re: ATA/Cdrom(?) panic X-BeenThere: freebsd-stable@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Production branch of FreeBSD source code List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 16 Nov 2011 15:04:10 -0000 On 16-11-2011 16:33, Alexander Motin wrote: > On 11/16/11 16:14, Bjoern A. Zeeb wrote: > > On Wed, 16 Nov 2011, Alexander Motin wrote: > > > >> Hi. > >> > >> On 11/16/11 08:43, Bjoern A. Zeeb wrote: > >>> we have seen this or a very similar panic for about 1 year now once in > >>> a while and I think I reported it before; this is FreeBSD as guest on > >>> vmware. Seems it was a double panic this time. Could someone please > >>> see what's going on there? It was on 8.x-STABLE in the past and this > >>> is 8.2-RELEASE-p4. > >> > >> The part of code reporting "completing request directly" is IMHO broken > >> by design. It returns request completion before request will actually be > >> completed by lower levels without any knowledge of what's going on > >> there. There is kind of protection against double request completion, > >> but it looks like not always working. May be because that part of code > >> is not locked and nothing prevents that semaphore timeout and normal > >> request timeout/completion to happen simultaneously. It is surprising to > >> see even two traps same time, not sure what synchronized them so > >> precisely. > >> > >> Simple removing that semaphore timeout is not an option, because it will > >> cause deadlock when this wait happen within taskqueue thread that is > >> used to handle requests completion and abort that wait. Avoid waiting > >> inside taskqueue is also impossible without major rewrite. That's why > >> ATA_CAM drops that code completely. > > > > So the bottom line of what you are saying is: > > 1) it's hard to fix right in 8 > > 2) it's not an issue in 9 anymore at all? > > Right. Hmm. We're running many FreeBSD 8.2 machines as guests in VMware but have never encountered the panic described above. Should I be worried? :-) -- Joel