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From: jss@sjuvax.UUCP (J. Shapiro)
Newsgroups: net.unix
Subject: Re: more on file \"attributes\"
Message-ID: <1238@sjuvax.UUCP>
Date: Mon, 5-Aug-85 00:29:25 EDT
Article-I.D.: sjuvax.1238
Posted: Mon Aug  5 00:29:25 1985
Date-Received: Tue, 6-Aug-85 08:54:08 EDT
References: <3403@decwrl.UUCP>
Organization: Haverford College, Haverford, Pa.
Lines: 37

Mr. Campbell has one point, at least, which should not be ignored. UNIX is
badly in need of some sort of semaphore structure for use between
processes which do not know about each other.  Without this facility,
it would be very difficult to write a library which could provide
reliable record locking, which is one of the facilities he needed
which is sorely lacking in current UNIX.  It seems to me, after admittedly
very little thought, that one of two things is needed:

	1) some sempahore facility which would have a namespace which
		would allow owner/group/world read/write priviledges.
		This would actually be generally useful, and current file
		primatives do not provide this facility in a resource
		efficient or reliable manner.

	2) a block level lock on a file, either physical block or logical
		block, preferably physical.

The first facility, I believe, is to be greatly preferred.  Please,
arguments about using pseudo devices or files in the file system or
pipes/sockets/wombats-carrying-postcards don't wash.  These are
neither resource efficient nor portable.  The semaphore facilities
necessary are not hard to implement (I have done them myself on other
systems), and would help a great deal in solving many problems of
record access, which contrary to popular opinion in UNIX land
constitutes a great deal of what is done out in the real business world.

To my knowledge, all of the database systems providing for reliable
record access do this by circumnavigating UNIX, which seems to me to
be a bit of a waste.

I enjoy using UNIX as a development environment, and I believe that
99% of its ideas are in theory right, but it has a few shortcomings.
Others have noticed the process synchronization shortcomings.  Has
anyone done anything about them?

Jon Shapiro
Haverford College