From owner-freebsd-hackers@FreeBSD.ORG Mon Jun 5 17:31:00 2006 Return-Path: X-Original-To: freebsd-hackers@freebsd.org Delivered-To: freebsd-hackers@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id C66A816B3DA for ; Mon, 5 Jun 2006 17:31:00 +0000 (UTC) (envelope-from kostikbel@gmail.com) Received: from fw.zoral.com.ua (ll-227.216.82.212.sovam.net.ua [212.82.216.227]) by mx1.FreeBSD.org (Postfix) with ESMTP id A9EC043D46 for ; Mon, 5 Jun 2006 17:30:59 +0000 (GMT) (envelope-from kostikbel@gmail.com) Received: from deviant.kiev.zoral.com.ua (root@deviant.kiev.zoral.com.ua [10.1.1.148]) by fw.zoral.com.ua (8.13.4/8.13.4) with ESMTP id k55HUkC3092997 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO); Mon, 5 Jun 2006 20:30:46 +0300 (EEST) (envelope-from kostikbel@gmail.com) Received: from deviant.kiev.zoral.com.ua (kostik@localhost [127.0.0.1]) by deviant.kiev.zoral.com.ua (8.13.6/8.13.6) with ESMTP id k55HUk0P056290; Mon, 5 Jun 2006 20:30:46 +0300 (EEST) (envelope-from kostikbel@gmail.com) Received: (from kostik@localhost) by deviant.kiev.zoral.com.ua (8.13.6/8.13.6/Submit) id k55HUjxU056289; Mon, 5 Jun 2006 20:30:45 +0300 (EEST) (envelope-from kostikbel@gmail.com) X-Authentication-Warning: deviant.kiev.zoral.com.ua: kostik set sender to kostikbel@gmail.com using -f Date: Mon, 5 Jun 2006 20:30:45 +0300 From: Konstantin Belousov To: Andrey Simonenko Message-ID: <20060605173045.GA45380@deviant.kiev.zoral.com.ua> References: <20060605110136.GA1348@pm513-1.comsys.ntu-kpi.kiev.ua> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="sm4nu43k4a2Rpi4c" Content-Disposition: inline In-Reply-To: <20060605110136.GA1348@pm513-1.comsys.ntu-kpi.kiev.ua> User-Agent: Mutt/1.4.2.1i X-Virus-Scanned: ClamAV version 0.88.2, clamav-milter version 0.88.2 on fw.zoral.com.ua X-Virus-Status: Clean X-Spam-Status: No, score=-1.4 required=5.0 tests=ALL_TRUSTED autolearn=failed version=3.1.1 X-Spam-Checker-Version: SpamAssassin 3.1.1 (2006-03-10) on fw.zoral.com.ua Cc: freebsd-hackers@freebsd.org Subject: Re: Question about synchronization (nfssvc, vfs_busy) X-BeenThere: freebsd-hackers@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Technical Discussions relating to FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 05 Jun 2006 17:31:05 -0000 --sm4nu43k4a2Rpi4c Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Mon, Jun 05, 2006 at 02:01:36PM +0300, Andrey Simonenko wrote: > 2. >=20 > If vfs_busy() is called without LK_NOWAIT flag, then it can sleep > if a filesystem is being unmounted. At some point unmount() will If vfs_busy() is called without LK_NOWAIT and fs is being unmounted, then vfs_busy returns with ENOENT error, isn't it ? > reach vfs_mount_destroy() and since there is one ref from vfs_busy() > it will sleep 3 seconds and will notice MNTK_MWAIT flag and wake up > a process, which is sleeping in vfs_busy(). How woken up process > can work with mount structure in vfs_busy() after wakeup(), which > could be already deallocated in vfs_mount_destroy()? vfs_busy() internally increases the ref count for mount point, so, it cannot be taken from under it (look for MNT_REF/MNT_REL). Simultameous entrance into the code in question in vfs_busy/vfs_mount_destroy is protected by mnt_mtx (MNT_ILOCK/MNT_IUNLOCK). --sm4nu43k4a2Rpi4c Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.3 (FreeBSD) iD8DBQFEhGpEC3+MBN1Mb4gRAhKLAKCzcwZcg0H7mlo5gt/FoSya8+HZMgCdGRBM QS+AKE9KhokSOoPDSb7Cxo8= =GDxq -----END PGP SIGNATURE----- --sm4nu43k4a2Rpi4c--