From owner-svn-src-head@FreeBSD.ORG Sat Jul 30 22:21:42 2011 Return-Path: Delivered-To: svn-src-head@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id B285A1065673; Sat, 30 Jul 2011 22:21:42 +0000 (UTC) (envelope-from mavbsd@gmail.com) Received: from mail-fx0-f54.google.com (mail-fx0-f54.google.com [209.85.161.54]) by mx1.freebsd.org (Postfix) with ESMTP id A932B8FC16; Sat, 30 Jul 2011 22:21:41 +0000 (UTC) Received: by fxe4 with SMTP id 4so4679438fxe.13 for ; Sat, 30 Jul 2011 15:21:40 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=sender:message-id:date:from:user-agent:mime-version:to:cc:subject :references:in-reply-to:x-enigmail-version:content-type :content-transfer-encoding; bh=svrrbO1T5fwIE/CZKzGJG8K96W1pZ/p0SkvY5YeXvgI=; b=k64bWIkVKpl23ZVpc23xTSUvWcNl6JiVECmeG4END4tpBIgVhXSghAzF2CbzivtW1A 6vMJXow37TRdsLsDc+/EL3jaY7pXyv6be3e33UkCaT5clCWDtE8RQb6BaRpGpInlbb2z JrXFcjp0dU4RiRvP1ILnB9i7d4KgfVUCtDHio= Received: by 10.223.76.17 with SMTP id a17mr3990825fak.32.1312064500404; Sat, 30 Jul 2011 15:21:40 -0700 (PDT) Received: from mavbook2.mavhome.dp.ua (pc.mavhome.dp.ua [212.86.226.226]) by mx.google.com with ESMTPS id g20sm1409032fai.45.2011.07.30.15.21.38 (version=SSLv3 cipher=OTHER); Sat, 30 Jul 2011 15:21:39 -0700 (PDT) Sender: Alexander Motin Message-ID: <4E3483D8.3060507@FreeBSD.org> Date: Sun, 31 Jul 2011 01:21:12 +0300 From: Alexander Motin User-Agent: Thunderbird 2.0.0.23 (X11/20091212) MIME-Version: 1.0 To: Andriy Gapon References: <201107292030.p6TKUSaf064895@svn.freebsd.org> <20110730163723.GZ17489@deviant.kiev.zoral.com.ua> <4E346DD9.5030902@FreeBSD.org> <4E3474CE.5090301@FreeBSD.org> In-Reply-To: <4E3474CE.5090301@FreeBSD.org> X-Enigmail-Version: 0.96.0 Content-Type: text/plain; charset=KOI8-R Content-Transfer-Encoding: 7bit Cc: svn-src-head@FreeBSD.org, svn-src-all@FreeBSD.org, src-committers@FreeBSD.org Subject: Re: svn commit: r224496 - head/sys/cam X-BeenThere: svn-src-head@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: SVN commit messages for the src tree for head/-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sat, 30 Jul 2011 22:21:42 -0000 Andriy Gapon wrote: > on 30/07/2011 23:47 Alexander Motin said the following: >> After many experiments I believe that problem is not related to this >> change. I've managed to reproduce it depending on GEOM modules >> registration order. After I disabled all GEOM modules and only geom_dev >> left, problem became persistent. Specifics of the geom_dev is that it >> opens device and closes it back without doing any I/O. That caused race >> condition between CCB allocation for FLUSHCACHE execution in adaclose() >> and higher-priority commands of device initialization sequence. Any I/O >> scheduled before adaclose() closed that race, making problem rare. The >> problem is specific to the ada, as for no other driver initialization >> and payload requests may intersect in time. > > somewhat contradicting your conclusions... can the following issue be also > caused by similar mechanics? > http://lists.freebsd.org/pipermail/freebsd-current/2010-October/020336.html Not sure, At least not exactly the same. cd driver keeps hold on device until probe completes, effectively blocking cdopen(). Seems there was a window in case of CD changers (closed month ago at r223557), but it should not affect plain CDs. Also, as soon as cd driver sends requests from cdopen(), not cdclose(), there would be much more chances to hit some global problem, as it would not depend on GEOM taste order. -- Alexander Motin