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/*
* Lock and unlock the database.
* Copyright (C) 1999, 2003 Lysator Academic Computer Association.
*
* This file is part of the LysKOM server.
*
* LysKOM is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 1, or (at your option)
* any later version.
*
* LysKOM is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* for more details.
*
* You should have received a copy of the GNU General Public License
* along with LysKOM; see the file COPYING. If not, write to
* Lysator, c/o ISY, Linkoping University, S-581 83 Linkoping, SWEDEN,
* or the Free Software Foundation, Inc., 675 Mass Ave, Cambridge,
* MA 02139, USA.
*
* Please report bugs at http://bugzilla.lysator.liu.se/.
*/
#include <config.h>
#include <sys/param.h>
#include <sys/types.h>
#include <unistd.h>
#include <errno.h>
#include <stdio.h>
#ifdef HAVE_STRING_H
# include <string.h>
#else
# ifdef HAVE_STRINGS_H
# include <strings.h>
# endif
#endif
#ifndef HAVE_STRCHR
# define strchr index
#endif
#include <stdlib.h>
#include <signal.h>
#include <netdb.h>
#include "timewrap.h"
#include "lockdb.h"
#include "log.h"
#include "kom-types.h"
#include "param.h"
#include "lyskomd.h"
int lock_db(void)
{
char *new_lock;
char *current_lock;
char *end;
int retry;
size_t sz;
size_t ix;
pid_t pid;
size_t lock_sz = 16;
do {
new_lock = malloc(lock_sz + 3 + 3 * sizeof(pid_t));
if (!new_lock) restart_kom("malloc failed (%d)\n", errno);
int ret = gethostname(new_lock, lock_sz);
if (ret == -1) {
if (errno == ENAMETOOLONG) {
free(new_lock);
lock_sz *= 2;
} else {
restart_kom("gethostname failed (%d)\n", errno);
}
} else break;
} while (1);
end = strchr(new_lock, '\0');
sprintf(end, ":%ld", (long)getpid());
for (retry = 0; retry < 2; ++retry)
{
if (symlink(new_lock, param.lockfile_name) == 0)
{
kom_log("Created lock %s\n", param.lockfile_name);
return 0;
}
if (errno != EEXIST)
restart_kom("Failed to create lock symlink %s "
"pointing to %s: %d\n", param.lockfile_name,
new_lock, errno);
if (retry)
{
kom_log("Lock file recreated by some other party\n");
return -1;
}
lock_sz = 16;
do {
current_lock = malloc(lock_sz);
sz = readlink(param.lockfile_name, current_lock, lock_sz);
if (sz >= lock_sz) {
free(current_lock);
lock_sz *= 2;
} else {
break;
}
} while (1);
current_lock[sz] = '\0';
for (ix = 0; ix < lock_sz && current_lock[ix] && new_lock[ix]; ++ix)
{
if (new_lock[ix] != current_lock[ix])
{
kom_log("Database already locked by %s\n", current_lock);
free(new_lock); free(current_lock);
return -1;
}
if (new_lock[ix] == ':')
break;
}
pid = strtol(¤t_lock[ix+1], &end, 10);
if (end == ¤t_lock[ix+1])
restart_kom("Found a broken lock symlink %s: %s\n",
param.lockfile_name, current_lock);
if (kill(pid, 0) == 0 || errno != ESRCH)
{
kom_log("Database already locked by %s\n", current_lock);
free(new_lock); free(current_lock);
return -1;
}
/* The process is dead. Remove the stale lock file. If it
was just removed by a dying process -- fine. */
if (remove(param.lockfile_name) < 0 && errno != ENOENT)
restart_kom("Failed to remove stale lock symlink %s\n",
param.lockfile_name);
else
kom_log("Removed stale lock file left by %s.\n", current_lock);
free(new_lock); free(current_lock);
}
restart_kom("Unreachable code reached in lock_db.\n");
}
void
unlock_db(void)
{
if (remove(param.lockfile_name) < 0)
restart_kom("Failed to remove lock file %s\n", param.lockfile_name);
}
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