niceSOFT/systemd: The systemd System and Service Manager

src/shared/async.h

27 строк1 KB

Daan De Meyer

tree-wide: Introduce sd-forward.h and shared-forward.h headers

16 окт 2025, 18:00

16 окт 2025, 18:00f102bc3

/* SPDX-License-Identifier: LGPL-2.1-or-later */
#pragma once

#include "shared-forward.h"

/* These functions implement various potentially slow operations that are executed asynchronously. They are
 * carefully written to not use pthreads, but use fork() or clone() (without CLONE_VM) so that the child does
 * not share any memory with the parent process, and thus cannot possibly interfere with the malloc()
 * synchronization locks.
 *
 * Background: glibc only synchronizes malloc() locks when doing fork(), but not when doing clone()
 * (regardless if through glibc's own wrapper or ours). This means if another thread in the parent has the
 * malloc() lock taken while a thread is cloning, the mutex will remain locked in the child (but the other
 * thread won't exist there), with no chance to ever be unlocked again. This will result in deadlocks. Hence
 * one has to make the choice: either never use threads in the parent, or never do memory allocation in the
 * child, or never use clone()/clone3() and stick to fork() only. Because we need clone()/clone3() we opted
 * for avoiding threads. */

int asynchronous_sync(PidRef *ret_pid);
int asynchronous_fsync(int fd, PidRef *ret_pid);

int asynchronous_close(int fd);
void asynchronous_close_many(const int fds[], size_t n_fds);

DEFINE_TRIVIAL_CLEANUP_FUNC(int, asynchronous_close);

int asynchronous_rm_rf(const char *p, RemoveFlags flags);