Date: Sun, 13 Jul 1997 12:49:09 -0400 (EDT) From: Chuck Robey <chuckr@glue.umd.edu> To: Simon Shapiro <Shimon@i-Connect.Net> Cc: freebsd-SCSI@FreeBSD.ORG, filo@yahoo.com, dg@root.com Subject: Re: problems with reboot Message-ID: <Pine.BSF.3.96.970713124429.256B-100000@Journey2.mat.net> In-Reply-To: <XFMail.970712182103.Shimon@i-Connect.Net>
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On Sat, 12 Jul 1997, Simon Shapiro wrote: > > Hi Chuck Robey; On 12-Jul-97 you wrote: > > ... > > > 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). I *think* the nfs failure was when I was learning how to correctly set up a 3C503 for NFS. Before I got that right, while experimenting, the second action on an mount going thru the 3C503 would hang, and a forcible umount would hang too. That was OK, I could just shut down the machine. I'm not sure here ... if your proposed fix would work on shutdown only, but allow a halt or reboot under emergency conditions, then I'm in agreement, and adding hooks to shutdown is a great path to take; if not, then you can see my objection here, right? ----------------------------+----------------------------------------------- Chuck Robey | Interests include any kind of voice or data chuckr@eng.umd.edu | communications topic, C programming, and Unix. 213 Lakeside Drive Apt T-1 | Greenbelt, MD 20770 | I run Journey2 and picnic, both FreeBSD (301) 220-2114 | version 3.0 current -- and great FUN! ----------------------------+-----------------------------------------------
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