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/*
* Ouroboros - Copyright (C) 2016 - 2021
*
* Lockfile for Ouroboros
*
* Dimitri Staessens <dimitri.staessens@ugent.be>
* Sander Vrijders <sander.vrijders@ugent.be>
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public License
* version 2.1 as published by the Free Software Foundation.
*
* This library 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
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., http://www.fsf.org/about/contact/.
*/
#define _POSIX_C_SOURCE 200112L
#include "config.h"
#include <ouroboros/lockfile.h>
#include <stdlib.h>
#include <unistd.h>
#include <fcntl.h>
#include <string.h>
#include <signal.h>
#include <assert.h>
#include <sys/mman.h>
#include <sys/stat.h>
#define LF_SIZE (sizeof(pid_t))
struct lockfile {
pid_t * pid;
};
struct lockfile * lockfile_create() {
int fd;
mode_t mask;
struct lockfile * lf = malloc(sizeof(*lf));
if (lf == NULL)
return NULL;
mask = umask(0);
fd = shm_open(SHM_LOCKFILE_NAME, O_CREAT | O_EXCL | O_RDWR, 0666);
if (fd == -1) {
free(lf);
return NULL;
}
umask(mask);
if (ftruncate(fd, LF_SIZE - 1) < 0) {
free(lf);
return NULL;
}
lf->pid = mmap(NULL,
LF_SIZE, PROT_READ | PROT_WRITE,
MAP_SHARED,
fd,
0);
close (fd);
if (lf->pid == MAP_FAILED) {
shm_unlink(SHM_LOCKFILE_NAME);
free(lf);
return NULL;
}
*lf->pid = getpid();
return lf;
}
struct lockfile * lockfile_open() {
int fd;
struct lockfile * lf = malloc(sizeof(*lf));
if (lf == NULL)
return NULL;
fd = shm_open(SHM_LOCKFILE_NAME, O_RDWR, 0666);
if (fd < 0) {
free(lf);
return NULL;
}
lf->pid = mmap(NULL,
LF_SIZE, PROT_READ | PROT_WRITE,
MAP_SHARED,
fd,
0);
close(fd);
if (lf->pid == MAP_FAILED) {
shm_unlink(SHM_LOCKFILE_NAME);
free(lf);
return NULL;
}
return lf;
}
void lockfile_close(struct lockfile * lf)
{
assert(lf);
munmap(lf->pid, LF_SIZE);
free(lf);
}
void lockfile_destroy(struct lockfile * lf)
{
assert(lf);
if (getpid() != *lf->pid && kill(*lf->pid, 0) == 0)
return;
munmap(lf->pid, LF_SIZE);
shm_unlink(SHM_LOCKFILE_NAME);
free(lf);
}
pid_t lockfile_owner(struct lockfile * lf)
{
assert(lf);
return *lf->pid;
}
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