+
+/*
+ * Code for locking/unlocking the serial device.
+ * This code is derived from chat.c.
+ */
+
+#ifndef LOCK_DIR
+# ifdef HDB
+# define PIDSTRING
+# define LOCK_PREFIX "/usr/spool/locks/LCK.."
+# else /* HDB */
+# define LOCK_PREFIX "/usr/spool/uucp/LCK.."
+# endif /* HDB */
+#endif /* LOCK_DIR */
+
+/*
+ * lock - create a lock file for the named device.
+ */
+int
+lock(dev)
+ char *dev;
+{
+ char hdb_lock_buffer[12];
+ int fd, pid, n;
+ char *p;
+
+ if ((p = strrchr(dev, '/')) != NULL)
+ dev = p + 1;
+ lock_file = malloc(strlen(LOCK_PREFIX) + strlen(dev) + 1);
+ if (lock_file == NULL)
+ novm("lock file name");
+ strcat(strcpy(lock_file, LOCK_PREFIX), dev);
+
+ while ((fd = open(lock_file, O_EXCL | O_CREAT | O_RDWR, 0644)) < 0) {
+ if (errno == EEXIST
+ && (fd = open(lock_file, O_RDONLY, 0)) >= 0) {
+ /* Read the lock file to find out who has the device locked */
+#ifdef PIDSTRING
+ n = read(fd, hdb_lock_buffer, 11);
+ if (n > 0) {
+ hdb_lock_buffer[n] = 0;
+ pid = atoi(hdb_lock_buffer);
+ }
+#else
+ n = read(fd, &pid, sizeof(pid));
+#endif
+ if (n <= 0) {
+ syslog(LOG_ERR, "Can't read pid from lock file %s", lock_file);
+ close(fd);
+ } else {
+ if (kill(pid, 0) == -1 && errno == ESRCH) {
+ /* pid no longer exists - remove the lock file */
+ if (unlink(lock_file) == 0) {
+ close(fd);
+ syslog(LOG_NOTICE, "Removed stale lock on %s (pid %d)",
+ dev, pid);
+ continue;
+ } else
+ syslog(LOG_WARNING, "Couldn't remove stale lock on %s",
+ dev);
+ } else
+ syslog(LOG_NOTICE, "Device %s is locked by pid %d",
+ dev, pid);
+ }
+ close(fd);
+ } else
+ syslog(LOG_ERR, "Can't create lock file %s: %m", lock_file);
+ free(lock_file);
+ lock_file = NULL;
+ return -1;
+ }
+
+#ifdef PIDSTRING
+ sprintf(hdb_lock_buffer, "%10d\n", getpid());
+ write(fd, hdb_lock_buffer, 11);
+#else
+ pid = getpid();
+ write(fd, &pid, sizeof pid);
+#endif
+
+ close(fd);
+ return 0;
+}
+
+/*
+ * Remove our lockfile
+ */
+unlock()
+{
+ if (lock_file) {
+ unlink(lock_file);
+ free(lock_file);
+ lock_file = NULL;
+ }
+}