Mercurial > trustbridge
view common/linuxlockfile.c @ 1332:8362e30f7b55
(issue139) Check that pid is not running if the lock can be aquired
If the lock on the lockfile can be aquired it might still be
possible that another process is running. So we read the
pid from the lockfile and check if another process with the
same installation prefix as us is running.
author | Andre Heinecke <andre.heinecke@intevation.de> |
---|---|
date | Wed, 15 Oct 2014 14:19:46 +0200 |
parents | 7ea3a4c0e2ae |
children | 5d7b1650de1f |
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/* Copyright (C) 2014 by Bundesamt für Sicherheit in der Informationstechnik * Software engineering by Intevation GmbH * * This file is Free Software under the GNU GPL (v>=2) * and comes with ABSOLUTELY NO WARRANTY! * See LICENSE.txt for details. */ #ifndef WIN32 #include <fcntl.h> #include <stdio.h> #include <sys/types.h> #include <unistd.h> #include <string.h> #include "logging.h" #include "util.h" #include "strhelp.h" int open_lockfile(char *path) { int fd; char pidstr[20]; size_t pidstrlen; struct flock lk; fd = open(path, O_RDWR | O_CREAT, 0600); if (fd != -1) { /* Get an exclusive lock on the whole file. */ lk.l_type = F_WRLCK; lk.l_whence = SEEK_SET; lk.l_start = 0; lk.l_len = 0; fcntl(fd, F_SETLK, &lk); if (fcntl(fd, F_SETLK, &lk) != -1) { char oldpid[20]; FILE *f = fopen(path, "r"); size_t bytes_read; if (f) { bytes_read = fread(oldpid, 1, sizeof(oldpid), f); if (bytes_read) { char *oldPath, *newPath; if (bytes_read == sizeof(oldpid)) { ERRORPRINTF ("Bad information in pidfile\n"); } else { oldpid[bytes_read] = '\0'; oldPath = get_proc_install_dir(oldpid); newPath = get_install_dir(); if (oldPath && newPath && strcmp(oldPath, newPath) == 0) { DEBUGPRINTF("Got lock but process from %s is still" "running.\n", oldPath); xfree(oldPath); xfree(newPath); return -1; } xfree(oldPath); xfree(newPath); } } fclose(f); } ftruncate(fd, 0); pidstrlen = (size_t)snprintf(pidstr, sizeof(pidstr), "%d", getpid()); write(fd, pidstr, pidstrlen); } else { /* Lock can not be acquired. Bail out... */ close(fd); DEBUGPRINTF("Could not get an exclusive lock on %s.\n", path); return -1; } } else { DEBUGPRINTF("Failed to open lock file: %s.\n", path); } return fd; } void close_lockfile(int fd) { struct flock lk; /* Delete the PID from file. */ /* We do this instead of trying to unlink the file. */ ftruncate(fd, 0); /* Remove lock from the file. */ lk.l_type = F_UNLCK; lk.l_whence = SEEK_SET; lk.l_start = 0; lk.l_len = 0; if (fcntl(fd, F_SETLK, &lk) == -1) { /* Lock can not be removed */ DEBUGPRINTF("Could not remove lock from pid file.\n"); } close(fd); } #endif /* Not WIN32 */