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/*
* lock.c - lock/unlock the serial device.
*
* This code is derived from chat.c.
*/
static char rcsid[] = "$Id$";
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <fcntl.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <syslog.h>
#ifdef sun
# if defined(SUNOS) && SUNOS >= 41
# ifndef HDB
# define HDB
# endif
# endif
#endif
#ifndef LOCK_DIR
# if defined(__NetBSD__) || defined(__FreeBSD__)
# define PIDSTRING
# define LOCK_PREFIX "/var/spool/lock/LCK.."
# else
# ifdef HDB
# define PIDSTRING
# define LOCK_PREFIX "/usr/spool/locks/LCK.."
# else /* HDB */
# define LOCK_PREFIX "/usr/spool/uucp/LCK.."
# endif /* HDB */
# endif
#endif /* LOCK_DIR */
static char *lock_file;
/*
* Create a lock file for the named lock 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;
}
}
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