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/*
* Ouroboros - Copyright (C) 2016 - 2024
*
* Lockfile for Ouroboros
*
* Dimitri Staessens <dimitri@ouroboros.rocks>
* Sander Vrijders <sander@ouroboros.rocks>
*
* 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))
#define LF_PROT (PROT_READ | PROT_WRITE)
struct lockfile {
pid_t * pid;
};
static struct lockfile * __lockfile_open(int oflag)
{
int fd;
struct lockfile * lf;
lf = malloc(sizeof(*lf));
if (lf == NULL)
goto fail_lockfile;
fd = shm_open(SHM_LOCKFILE_NAME, oflag, 0666);
if (fd == -1)
goto fail_shm_open;
if ((oflag & O_CREAT) && ftruncate(fd, LF_SIZE) < 0)
goto fail_truncate;
lf->pid = mmap(NULL, LF_SIZE, LF_PROT, MAP_SHARED, fd, 0);
if (lf->pid == MAP_FAILED)
goto fail_mmap;
close (fd);
return lf;
fail_mmap:
shm_unlink(SHM_LOCKFILE_NAME);
fail_truncate:
close(fd);
fail_shm_open:
free(lf);
fail_lockfile:
return NULL;
}
struct lockfile * lockfile_create(void)
{
struct lockfile * lf;
mode_t mask;
mask = umask(0);
lf = __lockfile_open(O_CREAT | O_EXCL | O_RDWR);
if (lf == NULL)
return NULL;
umask(mask);
*lf->pid = getpid();
return lf;
}
struct lockfile * lockfile_open(void)
{
return __lockfile_open(O_RDWR);
}
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;
lockfile_close(lf);
shm_unlink(SHM_LOCKFILE_NAME);
}
pid_t lockfile_owner(struct lockfile * lf)
{
assert(lf);
return *lf->pid;
}
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