Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.2 9/17/84; site opus.UUCP Path: utzoo!watmath!clyde!burl!ulysses!allegra!mit-eddie!godot!harvard!seismo!hao!cires!nbires!opus!rcd From: rcd@opus.UUCP (Dick Dunn) Newsgroups: net.unix,net.unix-wizards Subject: Re: Results of Locking Poll Message-ID: <911@opus.UUCP> Date: Fri, 19-Oct-84 02:06:22 EDT Article-I.D.: opus.911 Posted: Fri Oct 19 02:06:22 1984 Date-Received: Sun, 21-Oct-84 14:44:19 EDT References: <499@plus5.UUCP> Distribution: net Organization: NBI,Inc, Boulder CO Lines: 28 Xref: godot net.unix:1786 net.unix-wizards:3282 (Original only appeared in net.unix.) > Early in June I sent out a poll on the net to ask people what they wanted > in the way of file and/or record locking for Unix. >... > John Bass tells me that shared reads are hard to do under the currently > proposed lockf mechanism (1 process per "area" in the file. This "area" > can extend to EOF.). I don't yet see how this is difficult, but John > hasn't told me what the problem is. Note that this mechanism provides > only all-or-nothing locks, as opposed to shared/exclusive access, The one-process-per-area restriction seems almost by definition to preclude shared reading. Without shared read, it's not clear how useful the locking could be for databases--which are the most likely major candidate. As to the all-or-nothing aspect, I don't quite see how that can work out. It would seem that there would be a restriction on permissions before you can lock a file. But with an all/nothing lock, you either - require write permission and deny processes which only have/need read permission the right to read-lock a file to prevent modification while they're reading it. - require only read permission and allow processes to gain exclusive access to files which they don't "own" (in a colloquial sense). Doesn't sound very good. Clarification, please? -- Dick Dunn {hao,ucbvax,allegra}!nbires!rcd (303)444-5710 x3086 ...Lately it occurs to me what a long, strange trip it's been.