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From: ricko@sdcsvax.UCSD.EDU (Rick Ord)
Newsgroups: comp.sys.pyramid
Subject: flock on Pyramid OSx 4.0 and MH
Message-ID: <3757@sdcsvax.UCSD.EDU>
Date: Thu, 27-Aug-87 15:10:34 EDT
Article-I.D.: sdcsvax.3757
Posted: Thu Aug 27 15:10:34 1987
Date-Received: Sat, 29-Aug-87 11:53:11 EDT
Organization: University of California, San Diego
Lines: 65
Keywords: MH, flock, Pyramid OSx 4.0


Subject:
  MH and flock in Pyramid OSx 4.0

Disclaimer:
  I usually don't read comp.mail.mh so please disregard if this has been
posted before. I am cross-posting to comp.sys.pyramid even though Pyramid
does not include MH on their distribution tape.

Description:
  I recently put up the new Pyramid OSx 4.0 and had complaints from some users
about MH not working. In particular, simple commands like "inc" returned
errors indicating it could not open and lock their spooled mail file. It
turns out that Pyramid has incorporated the UCB flock and ATT lockf locking
mechanisms into the same vnode (inode) -level record locking routine. 
What this all means is that the functionality of ATT lockf is now imposed on 
UCB flock. 

  Under UCB's flock, you could throw an exclusive advisory lock on a file
openned for RDONLY. Under ATT's lockf, you can only throw an exclusive
advisory lock on a file openned for WRONLY or RDWR. As always, a shared lock
can be thrown on a file openned for RDONLY. 

  So, programs that had used flock to exclusively lock a file RDONLY will not 
work - MH is just such a program.

Fix:
  Below is a diff of /usr/src/new/mh/zotnet/mts/lock.c

Since this is library routine compiled into the utilities, you will have to
recompile and install from the top level after installing this fix.

Good Luck,
  Rick
-----------------------------------------------------------------------------
Rick Ord
UCSD Academic Computing Center
C-010  Rm. 1101-2A (APM)
La Jolla, Ca. 92093			UUCP:  ...sdcsvax!ricko
(619) 534-4067				ARPA:  ricko@sdcsvax.ucsd.edu
-----------------------------------------------------------------------------

RCS file: RCS/lock.c,v
retrieving revision 1.1
diff -c -r1.1 lock.c
*** /tmp/,RCSt1021950	Thu Aug 27 10:51:01 1987
--- lock.c	Thu Aug 27 10:50:37 1987
***************
*** 188,194
      for (i = 0; i < 5; i++) {
  	if ((fd = open (file, access | O_NDELAY)) == NOTOK)
  	    return NOTOK;
! 	if (flock (fd, LOCK_EX | LOCK_NB) != NOTOK)
  	    return fd;
  	j = errno;
  	(void) close (fd);

--- 188,194 -----
      for (i = 0; i < 5; i++) {
  	if ((fd = open (file, access | O_NDELAY)) == NOTOK)
  	    return NOTOK;
! 	if (flock (fd,((access ? LOCK_EX : LOCK_SH) | LOCK_NB)) != NOTOK)
  	    return fd;
  	j = errno;
  	(void) close (fd);