source: branches/samba-3.2.x/source/lib/pidfile.c

/* this code is broken - there is a race condition with the unlink (tridge) */

/* 
   Unix SMB/CIFS implementation.
   pidfile handling
   Copyright (C) Andrew Tridgell 1998
   
   This program 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 3 of the License, or
   (at your option) any later version.
   
   This program 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 this program.  If not, see <http://www.gnu.org/licenses/>.
*/

#include "includes.h"

#ifndef O_NONBLOCK
#define O_NONBLOCK
#endif

/* return the pid in a pidfile. return 0 if the process (or pidfile)
   does not exist */
pid_t pidfile_pid(const char *name)
{
        int fd;
        char pidstr[20];
        pid_t pid;
        unsigned int ret;
        char * pidFile;

        if (asprintf(&pidFile, "%s/%s.pid", lp_piddir(), name) == -1) {
                return 0;
        }

        fd = sys_open(pidFile, O_NONBLOCK | O_RDONLY, 0644);
        if (fd == -1) {
                SAFE_FREE(pidFile);
                return 0;
        }

        ZERO_ARRAY(pidstr);

        if (read(fd, pidstr, sizeof(pidstr)-1) <= 0) {
                goto noproc;
        }

        ret = atoi(pidstr);

        if (ret == 0) {
                /* Obviously we had some garbage in the pidfile... */
                DEBUG(1, ("Could not parse contents of pidfile %s\n",
                          pidFile));
                goto noproc;
        }
        
        pid = (pid_t)ret;
        if (!process_exists_by_pid(pid)) {
                goto noproc;
        }

#ifndef __OS2__ /* if we lock the file, we won't be able to read it later on OS/2 */
        if (fcntl_lock(fd,SMB_F_SETLK,0,1,F_RDLCK)) {
                /* we could get the lock - it can't be a Samba process */
                goto noproc;
        }
#endif
        SAFE_FREE(pidFile);
        close(fd);
        return (pid_t)ret;

 noproc:
        close(fd);
        unlink(pidFile);
        SAFE_FREE(pidFile);
        return 0;
}

/* create a pid file in the pid directory. open it and leave it locked */
void pidfile_create(const char *program_name)
{
        int     fd;
        char    buf[20];
        const char    *short_configfile;
        char *name;
        char *pidFile;
        pid_t pid;

#ifndef __OS2__
        /* Add a suffix to the program name if this is a process with a
         * none default configuration file name. */
        if (strcmp( CONFIGFILE, get_dyn_CONFIGFILE()) == 0) {
                name = SMB_STRDUP(program_name);
        } else {
                short_configfile = strrchr( get_dyn_CONFIGFILE(), '/');
                if (short_configfile == NULL) {
                        /* conf file in current directory */
                        short_configfile = get_dyn_CONFIGFILE();
                } else {
                        /* full/relative path provided */
                        short_configfile++;
                }
                if (asprintf(&name, "%s-%s", program_name,
                             short_configfile) == -1) {
                        smb_panic("asprintf failed");
                }
        }
#else
        /* On OS/2, CONFIGFILE will always be different to dyn_CONFIGFILE as dyn_CONFIGFILE dynamically looks up the system ETC directory */
        name = SMB_STRDUP(program_name);
#endif
        if (asprintf(&pidFile, "%s/%s.pid", lp_piddir(), name) == -1) {
                smb_panic("asprintf failed");
        }

        pid = pidfile_pid(name);
        if (pid != 0) {
                DEBUG(0,("ERROR: %s is already running. File %s exists and process id %d is running.\n", 
                         name, pidFile, (int)pid));
                exit(1);
        }

        fd = sys_open(pidFile, O_NONBLOCK | O_CREAT | O_WRONLY | O_EXCL, 0644);
        if (fd == -1) {
                DEBUG(0,("ERROR: can't open %s: Error was %s\n", pidFile, 
                         strerror(errno)));
                exit(1);
        }

        if (fcntl_lock(fd,SMB_F_SETLK,0,1,F_WRLCK)==False) {
                DEBUG(0,("ERROR: %s : fcntl lock of file %s failed. Error was %s\n",  
              name, pidFile, strerror(errno)));
                exit(1);
        }

        memset(buf, 0, sizeof(buf));
        slprintf(buf, sizeof(buf) - 1, "%u\n", (unsigned int) sys_getpid());
        if (write(fd, buf, strlen(buf)) != (ssize_t)strlen(buf)) {
                DEBUG(0,("ERROR: can't write to file %s: %s\n", 
                         pidFile, strerror(errno)));
                exit(1);
        }
        /* Leave pid file open & locked for the duration... */
        SAFE_FREE(name);
        SAFE_FREE(pidFile);
#ifdef __OS2__
        /* If we leave the file open & locked on OS/2 - we can't read it, so close the fd */
        close(fd);
#endif

}