From 55944e5e40b1be2afc4855d8d2baf4b73d1876b5 Mon Sep 17 00:00:00 2001 From: Daniel Baumann Date: Wed, 10 Apr 2024 22:49:52 +0200 Subject: Adding upstream version 255.4. Signed-off-by: Daniel Baumann --- src/shared/async.h | 26 ++++++++++++++++++++++++++ 1 file changed, 26 insertions(+) create mode 100644 src/shared/async.h (limited to 'src/shared/async.h') diff --git a/src/shared/async.h b/src/shared/async.h new file mode 100644 index 0000000..96148f9 --- /dev/null +++ b/src/shared/async.h @@ -0,0 +1,26 @@ +/* SPDX-License-Identifier: LGPL-2.1-or-later */ +#pragma once + +#include + +#include "macro.h" +#include "rm-rf.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(pid_t *ret_pid); +int asynchronous_close(int fd); +int asynchronous_rm_rf(const char *p, RemoveFlags flags); + +DEFINE_TRIVIAL_CLEANUP_FUNC(int, asynchronous_close); -- cgit v1.2.3