123 lines
2.5 KiB
C
123 lines
2.5 KiB
C
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/*
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* lock.c - lock/unlock the serial device.
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*
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* This code is derived from chat.c.
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*/
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static char rcsid[] = "$Id: lock.c,v 1.1 1994/05/14 18:39:39 cgd Exp $";
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#include <stdio.h>
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#include <string.h>
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#include <stdlib.h>
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#include <fcntl.h>
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#include <errno.h>
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#include <sys/types.h>
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#include <sys/stat.h>
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#include <syslog.h>
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#ifdef sun
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# if defined(SUNOS) && SUNOS >= 41
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# ifndef HDB
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# define HDB
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# endif
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# endif
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#endif
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#ifndef LOCK_DIR
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# ifdef __NetBSD__
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# define PIDSTRING
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# define LOCK_PREFIX "/var/spool/lock/LCK.."
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# else
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# ifdef HDB
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# define PIDSTRING
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# define LOCK_PREFIX "/usr/spool/locks/LCK.."
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# else /* HDB */
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# define LOCK_PREFIX "/usr/spool/uucp/LCK.."
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# endif /* HDB */
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# endif
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#endif /* LOCK_DIR */
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static char *lock_file;
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/*
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* Create a lock file for the named lock device
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*/
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int
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lock(dev)
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char *dev;
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{
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char hdb_lock_buffer[12];
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int fd, pid, n;
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char *p;
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if ((p = strrchr(dev, '/')) != NULL)
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dev = p + 1;
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lock_file = malloc(strlen(LOCK_PREFIX) + strlen(dev) + 1);
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if (lock_file == NULL)
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novm("lock file name");
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strcat(strcpy(lock_file, LOCK_PREFIX), dev);
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while ((fd = open(lock_file, O_EXCL | O_CREAT | O_RDWR, 0644)) < 0) {
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if (errno == EEXIST
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&& (fd = open(lock_file, O_RDONLY, 0)) >= 0) {
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/* Read the lock file to find out who has the device locked */
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#ifdef PIDSTRING
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n = read(fd, hdb_lock_buffer, 11);
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if (n > 0) {
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hdb_lock_buffer[n] = 0;
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pid = atoi(hdb_lock_buffer);
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}
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#else
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n = read(fd, &pid, sizeof(pid));
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#endif
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if (n <= 0) {
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syslog(LOG_ERR, "Can't read pid from lock file %s", lock_file);
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close(fd);
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} else {
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if (kill(pid, 0) == -1 && errno == ESRCH) {
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/* pid no longer exists - remove the lock file */
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if (unlink(lock_file) == 0) {
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close(fd);
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syslog(LOG_NOTICE, "Removed stale lock on %s (pid %d)",
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dev, pid);
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continue;
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} else
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syslog(LOG_WARNING, "Couldn't remove stale lock on %s",
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dev);
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} else
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syslog(LOG_NOTICE, "Device %s is locked by pid %d",
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dev, pid);
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}
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close(fd);
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} else
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syslog(LOG_ERR, "Can't create lock file %s: %m", lock_file);
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free(lock_file);
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lock_file = NULL;
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return -1;
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}
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# ifdef PIDSTRING
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sprintf(hdb_lock_buffer, "%10d\n", getpid());
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write(fd, hdb_lock_buffer, 11);
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# else
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pid = getpid();
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write(fd, &pid, sizeof pid);
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# endif
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close(fd);
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return 0;
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}
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/*
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* Remove our lockfile
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*/
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unlock()
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{
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if (lock_file) {
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unlink(lock_file);
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free(lock_file);
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lock_file = NULL;
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}
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}
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