NetBSD/lib/libutil/pidlock.c

243 lines
5.8 KiB
C

/* $NetBSD: pidlock.c,v 1.10 2002/11/16 23:30:32 itojun Exp $ */
/*
* Copyright 1996, 1997 by Curt Sampson <cjs@netbsd.org>.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
#include <sys/cdefs.h>
#if defined(LIBC_SCCS) && !defined(lint)
__RCSID("$NetBSD: pidlock.c,v 1.10 2002/11/16 23:30:32 itojun Exp $");
#endif /* LIBC_SCCS and not lint */
#include <sys/param.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <assert.h>
#include <errno.h>
#include <fcntl.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <util.h>
/*
* Create a lockfile. Return 0 when locked, -1 on error.
*/
int
pidlock(const char *lockfile, int flags, pid_t *locker, const char *info)
{
char tempfile[MAXPATHLEN];
char hostname[MAXHOSTNAMELEN + 1];
pid_t pid2 = -1;
struct stat st;
int err;
int f;
char s[256];
char *p;
_DIAGASSERT(lockfile != NULL);
/* locker may be NULL */
/* info may be NULL */
if (gethostname(hostname, sizeof(hostname)))
return -1;
hostname[sizeof(hostname) - 1] = '\0';
/*
* Build a path to the temporary file.
* We use the path with the PID and hostname appended.
* XXX This is not thread safe.
*/
if (snprintf(tempfile, sizeof(tempfile), "%s.%d.%s", lockfile,
(int) getpid(), hostname) >= sizeof(tempfile)) {
errno = ENAMETOOLONG;
return -1;
}
/* Open it, write pid, hostname, info. */
if ( (f = open(tempfile, O_WRONLY|O_CREAT|O_TRUNC, 0600)) == -1 ) {
err = errno;
unlink(tempfile);
errno = err;
return -1;
}
snprintf(s, sizeof(s), "%10d\n", getpid()); /* pid */
if (write(f, s, 11) != 11) {
err = errno;
close(f);
unlink(tempfile);
errno = err;
return -1;
}
if ((flags & PIDLOCK_USEHOSTNAME)) { /* hostname */
if ((write(f, hostname, strlen(hostname)) != strlen(hostname))
|| (write(f, "\n", 1) != 1)) {
err = errno;
close(f);
unlink(tempfile);
errno = err;
return -1;
}
}
if (info) { /* info */
if (!(flags & PIDLOCK_USEHOSTNAME)) {
/* write blank line because there's no hostname */
if (write(f, "\n", 1) != 1) {
err = errno;
close(f);
unlink(tempfile);
errno = err;
return -1;
}
}
if (write(f, info, strlen(info)) != strlen(info) ||
(write(f, "\n", 1) != 1)) {
err = errno;
close(f);
unlink(tempfile);
errno = err;
return -1;
}
}
close(f);
/* Hard link the temporary file to the real lock file. */
/* This is an atomic operation. */
lockfailed:
while (link(tempfile, lockfile) != 0) {
if (errno != EEXIST) {
err = errno;
unlink(tempfile);
errno = err;
return -1;
}
/* Find out who has this lockfile. */
if ((f = open(lockfile, O_RDONLY, 0)) != 0) {
read(f, s, 11);
pid2 = atoi(s);
read(f, s, sizeof(s)-2);
s[sizeof(s)-1] = '\0';
if ((p=strchr(s, '\n')) != NULL)
*p = '\0';
close(f);
if (!((flags & PIDLOCK_USEHOSTNAME) &&
strcmp(s, hostname))) {
if ((kill(pid2, 0) != 0) && (errno == ESRCH)) {
/* process doesn't exist */
unlink(lockfile);
continue;
}
}
}
if (flags & PIDLOCK_NONBLOCK) {
if (locker)
*locker = pid2;
unlink(tempfile);
errno = EWOULDBLOCK;
return -1;
} else
sleep(5);
}
/*
* Check to see that we really were successful (in case we're
* using NFS) by making sure that something really is linked
* to our tempfile (reference count is two).
*/
if (stat(tempfile, &st) != 0) {
err = errno;
/*
* We don't know if lockfile was really created by us,
* so we can't remove it.
*/
unlink(tempfile);
errno = err;
return -1;
}
if (st.st_nlink != 2)
goto lockfailed;
unlink(tempfile);
if (locker)
*locker = getpid(); /* return this process's PID on lock */
errno = 0;
return 0;
}
#define LOCKPATH "/var/spool/lock/LCK.."
#define DEVPATH "/dev/"
/*ARGSUSED*/
int
ttylock(const char *tty, int flags, pid_t *locker)
{
char lockfile[MAXPATHLEN];
char ttyfile[MAXPATHLEN];
struct stat sb;
_DIAGASSERT(tty != NULL);
/* locker is not used */
/* make sure the tty exists */
strlcpy(ttyfile, DEVPATH, sizeof(ttyfile));
strlcat(ttyfile, tty, sizeof(ttyfile));
if (stat(ttyfile, &sb)) {
errno = ENOENT; return -1;
}
if (!S_ISCHR(sb.st_mode)) {
errno = ENOENT; return -1;
}
/* do the lock */
strlcpy(lockfile, LOCKPATH, sizeof(lockfile));
strlcat(lockfile, tty, sizeof(lockfile));
return pidlock(lockfile, 0, 0, 0);
}
int
ttyunlock(const char *tty)
{
char lockfile[MAXPATHLEN];
char ttyfile[MAXPATHLEN];
struct stat sb;
_DIAGASSERT(tty != NULL);
/* make sure the tty exists */
strlcpy(ttyfile, DEVPATH, sizeof(ttyfile));
strlcat(ttyfile, tty, sizeof(ttyfile));
if (stat(ttyfile, &sb)) {
errno = ENOENT; return -1;
}
if (!S_ISCHR(sb.st_mode)) {
errno = ENOENT; return -1;
}
/* undo the lock */
strlcpy(lockfile, LOCKPATH, sizeof(lockfile));
strlcat(lockfile, tty, sizeof(lockfile));
return unlink(lockfile);
}