From owner-cvs-src@FreeBSD.ORG Fri Oct 5 01:26:39 2007 Return-Path: Delivered-To: cvs-src@FreeBSD.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 0638316A420; Fri, 5 Oct 2007 01:26:39 +0000 (UTC) (envelope-from jroberson@chesapeake.net) Received: from webaccess-cl.virtdom.com (webaccess-cl.virtdom.com [216.240.101.25]) by mx1.freebsd.org (Postfix) with ESMTP id C514E13C507; Fri, 5 Oct 2007 01:26:38 +0000 (UTC) (envelope-from jroberson@chesapeake.net) Received: from [192.168.1.103] (c-67-160-44-208.hsd1.wa.comcast.net [67.160.44.208]) (authenticated bits=0) by webaccess-cl.virtdom.com (8.13.6/8.13.6) with ESMTP id l951QaQs090135 (version=TLSv1/SSLv3 cipher=DHE-DSS-AES256-SHA bits=256 verify=NO); Thu, 4 Oct 2007 21:26:37 -0400 (EDT) (envelope-from jroberson@chesapeake.net) Date: Thu, 4 Oct 2007 18:29:25 -0700 (PDT) From: Jeff Roberson X-X-Sender: jroberson@10.0.0.1 To: John Baldwin In-Reply-To: <200710041219.13202.jhb@freebsd.org> Message-ID: <20071004182759.U912@10.0.0.1> References: <200710032106.l93L65bv095725@repoman.freebsd.org> <20071003164642.B615@10.0.0.1> <200710041219.13202.jhb@freebsd.org> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed Cc: cvs-src@FreeBSD.org, src-committers@FreeBSD.org, cvs-all@FreeBSD.org Subject: Re: cvs commit: src/sys/fs/devfs devfs_vnops.c src/sys/fs/fifofs fifo_vnops.c src/sys/kern uipc_usrreq.c vfs_vnops.c src/sys/vm vnode_pager.c X-BeenThere: cvs-src@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: CVS commit messages for the src tree List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 05 Oct 2007 01:26:39 -0000 On Thu, 4 Oct 2007, John Baldwin wrote: > On Wednesday 03 October 2007 07:48:00 pm Jeff Roberson wrote: >> On Wed, 3 Oct 2007, John Baldwin wrote: >> >>> jhb 2007-10-03 21:06:05 UTC >>> >>> FreeBSD src repository >>> >>> Modified files: (Branch: RELENG_6) >>> sys/fs/devfs devfs_vnops.c >>> sys/fs/fifofs fifo_vnops.c >>> sys/kern uipc_usrreq.c vfs_vnops.c >>> sys/vm vnode_pager.c >>> Log: >>> MFC: Always use an exclusive lock on the leaf vnode during an open() when >>> shared lookups are enabled. This closes a few races including a race > where >>> concurrent opens of a fifo could result in different v_fifoinfo > structures >>> in different threads. >> >> Long term we should really look for a better solution to this problem. >> There are a number of was to improve snapshots in ffs by fixing shared >> locking. > > I don't disagree. The fifo case can be fixed easily enough in the fifo code > by using fifo_mtx to protect v_fifoinfo perhaps (or doing an upgrade on the > vnode lock?), but for the MFC I didn't want to have to fix each of the races > with open(2). Probably better to fix it more properly in HEAD first. Definitely someting for head. Were there any others that you ran into besides v_fifoinfo? We should audit this more closely anyhow. I have been reluctant to push too much shared locking into VFS because it's not been so carefully studied. Jeff > > -- > John Baldwin >