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/* SPDX-License-Identifier: LGPL-2.1+ */
/***
This file is part of systemd.
Copyright 2013 Lennart Poettering
systemd is free software; you can redistribute it and/or modify it
under the terms of the GNU Lesser General Public License as published by
the Free Software Foundation; either version 2.1 of the License, or
(at your option) any later version.
systemd 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 systemd; If not, see <http://www.gnu.org/licenses/>.
***/
#include <errno.h>
#include <pthread.h>
#include <stddef.h>
#include <unistd.h>
#include "async.h"
#include "fd-util.h"
#include "log.h"
#include "macro.h"
#include "process-util.h"
#include "signal-util.h"
#include "util.h"
int asynchronous_job(void* (*func)(void *p), void *arg) {
pthread_attr_t a;
pthread_t t;
int r;
/* It kinda sucks that we have to resort to threads to
* implement an asynchronous sync(), but well, such is
* life.
*
* Note that issuing this command right before exiting a
* process will cause the process to wait for the sync() to
* complete. This function hence is nicely asynchronous really
* only in long running processes. */
r = pthread_attr_init(&a);
if (r > 0)
return -r;
r = pthread_attr_setdetachstate(&a, PTHREAD_CREATE_DETACHED);
if (r > 0)
goto finish;
r = pthread_create(&t, &a, func, arg);
finish:
pthread_attr_destroy(&a);
return -r;
}
int asynchronous_sync(void) {
pid_t pid;
/* This forks off an invocation of fork() as a child process, in order to initiate synchronization to
* disk. Note that we implement this as helper process rather than thread as we don't want the sync() to hang our
* original process ever, and a thread would do that as the process can't exit with threads hanging in blocking
* syscalls. */
log_debug("Spawning new process for sync");
pid = fork();
if (pid < 0)
return -errno;
if (pid == 0) {
/* Child process */
(void) rename_process("(sd-sync)");
(void) reset_all_signal_handlers();
(void) reset_signal_mask();
(void) close_all_fds(NULL, 0);
(void) sync();
_exit(EXIT_SUCCESS);
}
/* We don' really care about the PID from here on. It will exit when it's done. */
return 0;
}
static void *close_thread(void *p) {
assert_se(close_nointr(PTR_TO_FD(p)) != -EBADF);
return NULL;
}
int asynchronous_close(int fd) {
int r;
/* This is supposed to behave similar to safe_close(), but
* actually invoke close() asynchronously, so that it will
* never block. Ideally the kernel would have an API for this,
* but it doesn't, so we work around it, and hide this as a
* far away as we can. */
if (fd >= 0) {
PROTECT_ERRNO;
r = asynchronous_job(close_thread, FD_TO_PTR(fd));
if (r < 0)
assert_se(close_nointr(fd) != -EBADF);
}
return -1;
}
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