Re: SUMMARY: NFS mounting /var/spool/mail && file locking

From: Neal Becker (
Date: Fri Oct 02 1992 - 09:13:49 CDT

Just by cooincidence I was discussing this same subject on
smail3-users list. Here is an excerpt of a message
From: (Ronald S. Karr)
To: (Neal Becker)
Subject: Re: Retry local delivery?
Date: Thu, 1 Oct 92 15:31 PDT

>First let me say that I appreciate your advice. But I'm really lost
>on this point. I believe the local convention is to use file-based
>locking for mailboxes, ala /usr/mail/neal.lock. Won't this mechanism
>prevent any conflicts between reading and delivery, or two processes
>both attempting delivery?

The .lock file stuff doesn't work very well between systems. In
particular, it uses local-host pids for stale lock detection, and NFS
does not provide atomic operations that are necessary for the locking
model to work correctly. The problems relate to NFS's non-unix
semantics when operating between hosts. The situation isn't too bad if
only one user is getting a lock through NFS, at any one time. However,
locking from 50 hosts at the same time is really pushing your luck.

I guess this is enough to convince me.

This archive was generated by hypermail 2.1.2 : Fri Sep 28 2001 - 23:06:50 CDT