On Fri, 26 Jul 2002, at 10:09, Philip Hazel typed:
> The whole area of locking in Unix and Unix-like systems is a mess.
So I've been discovering :-(
> I see on the FreeBSD man page that "flock, lockf, and fcntl locks may safely
> be used concurrently" though it isn't clear what that actually means.
A quick test on 3.4-STABLE indicates that this means they do interoperate
nicely (i.e. they can't both get a write lock on the same file at the same
time).
> However, on Linux, they seem to be different.
The same applies on Compaq Tru64 (or whatever it's called this week) - on
both of these you can get seperate flock() and fcntl() write locks on the
same file at the same time.
> When I started on Exim, I got the impression that flock() was
> obsolescent, but I subsequently learned that some people have strong
> views about all of this, which is, I believe, why flock() is used in
> c-client.
Indeed, Mark Crispin seems to have "strong views" about a lot of things ;-)
(although he is fair - he describes the designers of both fcntl() and
flock() locking as cretins at various points in the c-client source...)
> The big question is: are you using NFS?
A world of no. Exim & imapd are both running on the same machine accessing
local disk.
mrj
--
Mark Rigby-Jones, Head of Systems, ts.com Ltd
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