Function posix_lock_file_open

src/daemon/service.c:486–507

}

static int posix_lock_file_open(const posix_log_path_t *path, bool *created_out) {
    int flags = O_RDWR | O_CLOEXEC | O_NOFOLLOW | O_NONBLOCK;
    int fd = openat(path->dir_fd, path->lock, flags | O_CREAT | O_EXCL, 0600);
    bool created = fd >= 0;
    if (fd < 0 && errno == EEXIST) {
        fd = openat(path->dir_fd, path->lock, flags);
    }
    struct stat status;
    struct stat by_path;
    if (fd < 0 || !fd_cloexec(fd) || !fd_regular_current_user(fd, &status) ||
        fchmod(fd, 0600) != 0 ||
        fstatat(path->dir_fd, path->lock, &by_path, AT_SYMLINK_NOFOLLOW) != 0 ||
        !S_ISREG(by_path.st_mode) || by_path.st_uid != geteuid() || by_path.st_nlink != 1 ||
        status.st_dev != by_path.st_dev || status.st_ino != by_path.st_ino) {
        if (fd >= 0) {
            (void)close(fd);
        }
        return -1;
    }
    *created_out = created;
    return fd;
}

static bool posix_lock_exclusive(int fd) {
    while (flock(fd, LOCK_EX) != 0) {