Path: utzoo!utgpu!cunews!bnrgate!brchh104!brchs1!bnr.ca!rice.edu!sun-spots-request
From: david@bdt.com (David Beckemeyer)
Newsgroups: comp.sys.sun
Subject: Sun NFS file locking
Keywords: No Digest Subjects during Flush
Message-ID: <4113@brchh104.bnr.ca>
Date: 27 Jun 91 20:22:00 GMT
Sender: news@brchh104.bnr.ca
Organization: Sunspots, Flush Mode
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Approved: sun-spots@rice.edu
X-Original-Date:    Tue, 18 Jun 1991 23:12:50 GMT

I have a network application which must be able to obtain exclusive
access to a file.   Following the Sun manuals, I'm using hte fcntl()
system call, as follows:

        /* Use fcntl to lock the master control file */
        sprintf(tmpnam, "%s/LOCKCTL", dir);
        lckfd = open(tmpnam, 2);
        if (lckfd < 0)
                return(seterror("mklock: cannot open LOCKCTL"));
        /* lock the whole file for exclusive use */
        lck.l_type = F_WRLCK;
        lck.l_whence = 0;
        lck.l_start = 0;
        lck.l_len = 0;
        if (fcntl(lckfd, F_SETLK, &lck)) {
                close(lckfd);
                return(seterror("mklock: F_SETLK failed"));
        }

The problems are that sometimes a process will hang in the
fcntl() call; ps reports that the process is in the D state
and the WCHAN is "socket".   What is going on?   It seems
like the rcp.lockd process gets confused under certain
circumstances.   What makes this happen and how does one
avoid it?  Is there a reliable way to lock files over the
network with SunOS?
-- 
David Beckemeyer (david@bdt.COM)	| "Lester Moore - Four slugs from a .44
Beckemeyer Development Tools		|  no Les, no more."
P.O. Box 21575, Oakland, CA 94620	|   - Headstone at Boot Hill
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