Path: utzoo!utgpu!attcan!uunet!mcvax!kunivv1!jaap
From: jaap@kunivv1.sci.kun.nl (Jaap Bril)
Newsgroups: news.software.b
Subject: locking in inews (2.11)
Keywords: inews locking
Message-ID: <257@kunivv1.sci.kun.nl>
Date: 26 Jul 88 14:42:19 GMT
Organization: University of Nijmegen, The Netherlands.
Lines: 56


Finding a extremely large queue on our news-system I discovered a dead-lock.
As the comment in the code did not mention the other program by name, I did
some trial and error.
The following hack had inews exiting on EWOULDBLOCK about ten times and then
doing its job.
** Code from ifuncs.c (news_2.11)
** /*
**  * Newsystem locking.
**  */
** 
** #if defined(BSD4_2) || defined(LOCKF)
** #ifdef LOCKF
** #include <unistd.h>
** #else /* !LOCKF */
** #include <sys/file.h>
** #endif /* !LOCKF */
** static int LockFd = -1;
** lock()
** {
** 	LockFd = open(SUBFILE, 2);
** 	if (LockFd < 0)
** 		logerr("Can't open(%s,2) to lock", SUBFILE);
** 	/* This will sleep until the other program releases the lock */
** 	/* We may need to alarm out of this, but I don't think so */
** #ifdef LOCKF
** 	if (lockf(LockFd, F_LOCK, 0) < 0)
** #else
** /* added LOCK_NB JBCH */
** 	 if (flock(LockFd, LOCK_EX|LOCK_NB ) < 0)
**	                          ^^^^^^^^
** #endif
** 		xerror("Can't get lock on %s: %s", SUBFILE, errmsg(errno));
** }
** 
** unlock()
** {
** 	(void) close(LockFd);
** }
** #else /* !BSD4_2 */

Inews has been taking care of the backlog now for about a full day
(being restarted when I got tired of the messages) and has not exited again.
Could someone please enlighten me on the following points:

1. which is the other program?
2. why a lock in the first place?
3. can I safely assume inews is now processing correctly?

As I can't determine the importance (stupidity ?) of the question please
email or followup as appropriate.
-- 
*Jaap Bril                                 * mcvax!kunivv1!jaap               * 
*computer&communicatie zaken               *                                  *
*faculteit wiskunde en natuurwetenschappen *                                  *
*KU Nijmegen, The Netherlands              *                                  *