254 lines
7.4 KiB
C
254 lines
7.4 KiB
C
/* SPDX-License-Identifier: MIT OR X11
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*
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* Copyright © 2024 Enrico Weigelt, metux IT consult <info@metux.net>
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*/
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/*
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Copyright 1987, 1998 The Open Group
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Permission to use, copy, modify, distribute, and sell this software and its
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documentation for any purpose is hereby granted without fee, provided that
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the above copyright notice appear in all copies and that both that
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copyright notice and this permission notice appear in supporting
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documentation.
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The above copyright notice and this permission notice shall be included
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in all copies or substantial portions of the Software.
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THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
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OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
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MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
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IN NO EVENT SHALL THE OPEN GROUP BE LIABLE FOR ANY CLAIM, DAMAGES OR
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OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
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ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
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OTHER DEALINGS IN THE SOFTWARE.
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Except as contained in this notice, the name of The Open Group shall
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not be used in advertising or otherwise to promote the sale, use or
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other dealings in this Software without prior written authorization
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from The Open Group.
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Copyright 1987 by Digital Equipment Corporation, Maynard, Massachusetts,
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Copyright 1994 Quarterdeck Office Systems.
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All Rights Reserved
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Permission to use, copy, modify, and distribute this software and its
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documentation for any purpose and without fee is hereby granted,
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provided that the above copyright notice appear in all copies and that
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both that copyright notice and this permission notice appear in
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supporting documentation, and that the names of Digital and
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Quarterdeck not be used in advertising or publicity pertaining to
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distribution of the software without specific, written prior
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permission.
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DIGITAL AND QUARTERDECK DISCLAIM ALL WARRANTIES WITH REGARD TO THIS
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SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND
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FITNESS, IN NO EVENT SHALL DIGITAL BE LIABLE FOR ANY SPECIAL, INDIRECT
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OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS
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OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
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OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE
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OR PERFORMANCE OF THIS SOFTWARE.
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*/
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#include <dix-config.h>
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#include <errno.h>
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#include <fcntl.h>
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#include <stdbool.h>
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#include <string.h>
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#include <sys/stat.h>
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#include <unistd.h>
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#include "dix/dix_priv.h"
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#include "os/serverlock.h"
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#include "os/osdep.h"
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#include "os.h"
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#include "opaque.h"
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/*
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* Explicit support for a server lock file like the ones used for UUCP.
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* For architectures with virtual terminals that can run more than one
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* server at a time. This keeps the servers from stomping on each other
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* if the user forgets to give them different display numbers.
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*/
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#define LOCK_DIR "/tmp"
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#define LOCK_TMP_PREFIX "/.tX"
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#define LOCK_PREFIX "/.X"
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#define LOCK_SUFFIX "-lock"
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#ifdef LOCK_SERVER
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static Bool StillLocking = FALSE;
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static char LockFile[PATH_MAX];
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static Bool nolock = FALSE;
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/*
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* LockServer --
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* Check if the server lock file exists. If so, check if the PID
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* contained inside is valid. If so, then die. Otherwise, create
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* the lock file containing the PID.
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*/
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void
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LockServer(void)
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{
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char tmp[PATH_MAX], pid_str[12];
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int lfd, i, haslock, l_pid, t;
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const char *tmppath = LOCK_DIR;
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int len;
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char port[20];
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if (nolock || NoListenAll)
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return;
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/*
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* Path names
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*/
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snprintf(port, sizeof(port), "%d", atoi(display));
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len = strlen(LOCK_PREFIX) > strlen(LOCK_TMP_PREFIX) ? strlen(LOCK_PREFIX) :
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strlen(LOCK_TMP_PREFIX);
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len += strlen(tmppath) + strlen(port) + strlen(LOCK_SUFFIX) + 1;
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if (len > sizeof(LockFile))
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FatalError("Display name `%s' is too long\n", port);
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(void) sprintf(tmp, "%s" LOCK_TMP_PREFIX "%s" LOCK_SUFFIX, tmppath, port);
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(void) sprintf(LockFile, "%s" LOCK_PREFIX "%s" LOCK_SUFFIX, tmppath, port);
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/*
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* Create a temporary file containing our PID. Attempt three times
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* to create the file.
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*/
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StillLocking = TRUE;
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i = 0;
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do {
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i++;
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lfd = open(tmp, O_CREAT | O_EXCL | O_WRONLY, 0644);
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if (lfd < 0)
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sleep(2);
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else
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break;
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} while (i < 3);
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if (lfd < 0) {
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unlink(tmp);
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i = 0;
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do {
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i++;
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lfd = open(tmp, O_CREAT | O_EXCL | O_WRONLY, 0644);
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if (lfd < 0)
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sleep(2);
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else
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break;
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} while (i < 3);
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}
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if (lfd < 0)
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FatalError("Could not create lock file in %s\n", tmp);
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snprintf(pid_str, sizeof(pid_str), "%10lu\n", (unsigned long) getpid());
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if (write(lfd, pid_str, 11) != 11)
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FatalError("Could not write pid to lock file in %s\n", tmp);
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(void) fchmod(lfd, 0444);
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(void) close(lfd);
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/*
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* OK. Now the tmp file exists. Try three times to move it in place
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* for the lock.
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*/
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i = 0;
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haslock = 0;
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while ((!haslock) && (i++ < 3)) {
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haslock = (link(tmp, LockFile) == 0);
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if (haslock) {
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/*
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* We're done.
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*/
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break;
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}
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else if (errno == EEXIST) {
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/*
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* Read the pid from the existing file
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*/
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lfd = open(LockFile, O_RDONLY | O_NOFOLLOW);
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if (lfd < 0) {
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unlink(tmp);
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FatalError("Can't read lock file %s\n", LockFile);
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}
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pid_str[0] = '\0';
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if (read(lfd, pid_str, 11) != 11) {
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/*
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* Bogus lock file.
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*/
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unlink(LockFile);
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close(lfd);
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continue;
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}
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pid_str[11] = '\0';
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sscanf(pid_str, "%d", &l_pid);
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close(lfd);
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/*
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* Now try to kill the PID to see if it exists.
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*/
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errno = 0;
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t = kill(l_pid, 0);
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if ((t < 0) && (errno == ESRCH)) {
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/*
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* Stale lock file.
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*/
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unlink(LockFile);
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continue;
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}
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else if (((t < 0) && (errno == EPERM)) || (t == 0)) {
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/*
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* Process is still active.
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*/
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unlink(tmp);
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FatalError
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("Server is already active for display %s\n%s %s\n%s\n",
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port, "\tIf this server is no longer running, remove",
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LockFile, "\tand start again.");
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}
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}
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else {
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unlink(tmp);
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FatalError
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("Linking lock file (%s) in place failed: %s\n",
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LockFile, strerror(errno));
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}
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}
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unlink(tmp);
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if (!haslock)
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FatalError("Could not create server lock file: %s\n", LockFile);
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StillLocking = FALSE;
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}
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/*
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* UnlockServer --
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* Remove the server lock file.
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*/
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void
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UnlockServer(void)
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{
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if (nolock || NoListenAll)
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return;
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if (!StillLocking) {
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(void) unlink(LockFile);
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}
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}
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void DisableServerLock(void) {
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nolock = TRUE;
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}
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void LockServerUseMsg(void) {
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ErrorF("-nolock disable the locking mechanism\n");
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}
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#else /* LOCK_SERVER */
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void LockServer(void) {}
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void UnlockServer(void) {}
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void DisableServerLock(void) {}
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void LockServerUseMsg(void) {}
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#endif /* LOCK_SERVER */
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