Path: utzoo!telly!attcan!uunet!tut.cis.ohio-state.edu!THEORY.LCS.MIT.EDU!rivest
From: rivest@THEORY.LCS.MIT.EDU
Newsgroups: gnu.emacs.bug
Subject: Emacs bug?
Message-ID: <8902200431.AA00394@flamingo.LCS.MIT.EDU>
Date: 20 Feb 89 04:31:05 GMT
Sender: daemon@tut.cis.ohio-state.edu
Distribution: gnu
Organization: GNUs Not Usenet
Lines: 44


Hi --

The version of emacs that the LCS Theory group is using,
(18.50.16 of Mon Oct 24 1988 on allspice) seems to be having problems
with properly detecting whether or not the disk version of a file in a
buffer has been changed.  More precisely, it frequently reports the
error message:
	"File on disk has changed, ..."
when in fact the only program manipulating that file is emacs itself.  

This occurs most frequently during the use of rmail, but it can also be
triggered by an auto-save of a file being edited.  (The most common occurence
is when it is writing back the RMAIL file after having retrieved some new
messages.)

I'm not able to force this to occur in any deterministic manner, so I can't
give you a simple sequence of commands to execute to cause it to appear.
Nonetheless, it occurs all too frequently.  

It may be important to note that most users of the theory group use NFS 
as provided by the "allspice system" in such a way that all files accessed
by emacs are stored on a remote file server.  It is conceivable that the bug
is somehow an NFS bug and not an EMACS bug, or that it is due to some 
unfortunate interaction between NFS and EMACS.  Ray and I have experimented
to see if it might be due to clock skew between the client and the server;
our experiments indicate that this is unlikely to be the cause.

The bug appeared recently when Ray Hirschfeld reconciled our server 
(theory) with the allspice system.  This primarily brought in the X11
system to all the theory machines (although some had been running X11
previously).  It is probably not an X problem, since it has appeared
when I was logged from a modem from a dumb terminal.  

I know this is not a crisp bug report, but the bug is not a crisp one
either.  

	-- Is this a known problem?  If so, is there a known fix?

I will attempt to gather more information on this problem, but would
appreciate any information or guidance you may have at this point...

	Thanks!
	Ron Rivest