From owner-freebsd-scsi Sat Jul 12 18:21:26 1997 Return-Path: Received: (from root@localhost) by hub.freebsd.org (8.8.5/8.8.5) id SAA28249 for freebsd-scsi-outgoing; Sat, 12 Jul 1997 18:21:26 -0700 (PDT) Received: from sendero-ppp.i-connect.net (sendero-ppp.i-Connect.Net [206.190.143.100]) by hub.freebsd.org (8.8.5/8.8.5) with SMTP id SAA28232 for ; Sat, 12 Jul 1997 18:21:07 -0700 (PDT) Received: (qmail 27240 invoked by uid 1000); 13 Jul 1997 01:21:03 -0000 Message-ID: X-Mailer: XFMail 1.2-alpha [p0] on FreeBSD Content-Type: text/plain; charset=iso-8859-8 Content-Transfer-Encoding: 8bit MIME-Version: 1.0 In-Reply-To: Date: Sat, 12 Jul 1997 18:21:03 -0700 (PDT) Organization: Atlas Telecom From: Simon Shapiro To: Chuck Robey Subject: Re: problems with reboot Cc: freebsd-SCSI@FreeBSD.ORG, filo@yahoo.com, dg@root.com Sender: owner-freebsd-scsi@FreeBSD.ORG X-Loop: FreeBSD.org Precedence: bulk Hi Chuck Robey; On 12-Jul-97 you wrote: ... > > Under normal operation, it generates the SCSI ``ALLOW MEDIA REMOVAL'', > > which the DPT blocks until it is done flushing and invalidating. > > I personally never have this problem on any of our machines, but... > > Is this always safe? I've had some instances where a umount call simply > hung, and never returned. I think they were either nfs or msdos mounts > that gave this trouble, but the umount call could not be kill'ed, and > making shutdown wait? Would halt still work, as an emergency measure? > I know the FSs that were hung wouldn't be closed, but at least my ufs FSs > would be clean. Network Failure system is a special case (i AM being nice :-); It is supposedly stateless and the mount is a client and thus not governing physical I/O. a shutdown can (should) probably force a umount. Even on a local system, a forced umount is OK. It is a FS issue. But if the fs layer calls a function that by definition blocks, it is ``none of the caller's business'' how/what the callee does and how long it takes. To assume anything on the nature if a callee's internals is not a good idea. Here we have a live exapmple (why it is a bad idea). Simon