Use pidfile(3) in cron(8).

Note, that when cron(8) cannot create pidfile, it'll exit. I didn't
changed this behaviour, but its better to ignore errors other than
EEXIST, so daemon can be started on systems where /var/ file system
doesn't support locking (like NFS without rpc.lockd(8)).

usr.sbin/cron/cron/cron.c

@@ -46,6 +46,7 @@ static	void	usage __P((void)),
 
 static time_t	last_time = 0;
 static int	dst_enabled = 0;
+struct pidfh *pfh;
 
 static void
 usage() {
@@ -63,6 +64,28 @@ usage() {
 	exit(ERROR_EXIT);
 }
 
+static void
+open_pidfile(void)
+{
+	char	pidfile[MAX_FNAME];
+	char	buf[MAX_TEMPSTR];
+	int	otherpid;
+
+	(void) snprintf(pidfile, sizeof(pidfile), PIDFILE, PIDDIR);
+	pfh = pidfile_open(pidfile, 0644, &otherpid);
+	if (pfh == NULL) {
+		if (errno == EEXIST) {
+			snprintf(buf, sizeof(buf),
+			    "cron already running, pid: %d", otherpid);
+		} else {
+			snprintf(buf, sizeof(buf),
+			    "can't open or create %s: %s", pidfile,
+			    strerror(errno));
+		}
+		log_it("CRON", getpid(), "DEATH", buf);
+		errx(ERROR_EXIT, "%s", buf);
+	}
+}
 
 int
 main(argc, argv)
@@ -87,7 +110,7 @@ main(argc, argv)
 #endif
 	(void) signal(SIGHUP, sighup_handler);
 
-	acquire_daemonlock(0);
+	open_pidfile();
 	set_cron_uid();
 	set_cron_cwd();
 
@@ -105,12 +128,13 @@ main(argc, argv)
 		(void) fprintf(stderr, "[%d] cron started\n", getpid());
 	} else {
 		if (daemon(1, 0) == -1) {
+			pidfile_remove(pfh);
 			log_it("CRON",getpid(),"DEATH","can't become daemon");
 			exit(0);
 		}
 	}
 
-	acquire_daemonlock(0);
+	pidfile_write(pfh);
 	database.head = NULL;
 	database.tail = NULL;
 	database.mtime = (time_t) 0;

usr.sbin/cron/cron/cron.h

@@ -34,6 +34,7 @@
 #include <ctype.h>
 #include <err.h>
 #include <errno.h>
+#include <libutil.h>
 #include <pwd.h>
 #include <signal.h>
 #include <stdio.h>
@@ -210,7 +211,6 @@ void		set_cron_uid __P((void)),
 		env_free __P((char **)),
 		unget_char __P((int, FILE *)),
 		free_entry __P((entry *)),
-		acquire_daemonlock __P((int)),
 		skip_comments __P((FILE *)),
 		log_it __P((char *, int, char *, char *)),
 		log_close __P((void));
@@ -289,6 +289,7 @@ extern	int	LineNumber;
 extern unsigned	Jitter,
 		RootJitter;
 extern	time_t	TargetTime;
+extern struct pidfh *pfh;
 # if DEBUGGING
 extern	int	DebugFlags;
 extern	char	*DebugFlagNames[];

usr.sbin/cron/cron/do_command.c

@@ -59,7 +59,7 @@ do_command(e, u)
 		break;
 	case 0:
 		/* child process */
-		acquire_daemonlock(1);
+		pidfile_close(pfh);
 		child_process(e, u);
 		Debug(DPROC, ("[%d] child process done, exiting\n", getpid()))
 		_exit(OK_EXIT);

usr.sbin/cron/lib/misc.c

@@ -222,65 +222,6 @@ set_cron_cwd()
 }
 
 
-/* acquire_daemonlock() - write our PID into /etc/cron.pid, unless
- *	another daemon is already running, which we detect here.
- *
- * note: main() calls us twice; once before forking, once after.
- *	we maintain static storage of the file pointer so that we
- *	can rewrite our PID into the PIDFILE after the fork.
- *
- * it would be great if fflush() disassociated the file buffer.
- */
-void
-acquire_daemonlock(closeflag)
-	int closeflag;
-{
-	static	FILE	*fp = NULL;
-
-	if (closeflag && fp) {
-		fclose(fp);
-		fp = NULL;
-		return;
-	}
-
-	if (!fp) {
-		char	pidfile[MAX_FNAME];
-		char	buf[MAX_TEMPSTR];
-		int	fd, otherpid;
-
-		(void) sprintf(pidfile, PIDFILE, PIDDIR);
-		if ((-1 == (fd = open(pidfile, O_RDWR|O_CREAT, 0644)))
-		    || (NULL == (fp = fdopen(fd, "r+")))
-		    ) {
-			sprintf(buf, "can't open or create %s: %s",
-				pidfile, strerror(errno));
-			log_it("CRON", getpid(), "DEATH", buf);
-			errx(ERROR_EXIT, "%s", buf);
-		}
-
-		if (flock(fd, LOCK_EX|LOCK_NB) < OK) {
-			int save_errno = errno;
-
-			fscanf(fp, "%d", &otherpid);
-			sprintf(buf, "can't lock %s, otherpid may be %d: %s",
-				pidfile, otherpid, strerror(save_errno));
-			log_it("CRON", getpid(), "DEATH", buf);
-			errx(ERROR_EXIT, "%s", buf);
-		}
-
-		(void) fcntl(fd, F_SETFD, 1);
-	}
-
-	rewind(fp);
-	fprintf(fp, "%d\n", getpid());
-	fflush(fp);
-	(void) ftruncate(fileno(fp), ftell(fp));
-
-	/* abandon fd and fp even though the file is open. we need to
-	 * keep it open and locked, but we don't need the handles elsewhere.
-	 */
-}
-
 /* get_char(file) : like getc() but increment LineNumber on newlines
  */
 int