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https://github.com/jart/cosmopolitan.git
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60cb435cb4
If threads are being used, then fork() will now acquire and release and runtime locks so that fork() may be safely used from threads. This also makes vfork() thread safe, because pthread mutexes will do nothing when the process is a child of vfork(). More torture tests have been written to confirm this all works like a charm. Additionally: - Invent hexpcpy() api - Rename nsync_malloc_() to kmalloc() - Complete posix named semaphore implementation - Make pthread_create() asynchronous signal safe - Add rm, rmdir, and touch to command interpreter builtins - Invent sigisprecious() and modify sigset functions to use it - Add unit tests for posix_spawn() attributes and fix its bugs One unresolved problem is the reclaiming of *NSYNC waiter memory in the forked child processes, within apps which have threads waiting on locks
84 lines
3.7 KiB
C
84 lines
3.7 KiB
C
/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
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│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8 :vi│
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╞══════════════════════════════════════════════════════════════════════════════╡
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│ Copyright 2022 Justine Alexandra Roberts Tunney │
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│ │
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│ Permission to use, copy, modify, and/or distribute this software for │
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│ any purpose with or without fee is hereby granted, provided that the │
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│ above copyright notice and this permission notice appear in all copies. │
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│ │
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│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL │
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│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED │
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│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE │
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│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL │
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│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR │
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│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER │
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│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR │
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│ PERFORMANCE OF THIS SOFTWARE. │
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╚─────────────────────────────────────────────────────────────────────────────*/
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#include "libc/intrin/weaken.h"
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#include "libc/thread/posixthread.internal.h"
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#include "libc/thread/thread.h"
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/**
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* Registers fork() handlers.
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*
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* Parent and child functions are called in the same order they're
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* registered. Prepare functions are called in reverse order.
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*
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* Here's an example of how pthread_atfork() can be used:
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*
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* static struct {
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* pthread_once_t once;
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* pthread_mutex_t lock;
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* // data structures...
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* } g_lib;
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*
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* static void lib_lock(void) {
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* pthread_mutex_lock(&g_lib.lock);
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* }
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*
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* static void lib_unlock(void) {
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* pthread_mutex_unlock(&g_lib.lock);
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* }
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*
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* static void lib_funlock(void) {
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* pthread_mutex_init(&g_lib.lock, 0);
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* }
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*
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* static void lib_setup(void) {
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* lib_funlock();
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* pthread_atfork(lib_lock, lib_unlock, lib_funlock);
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* }
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*
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* static void lib_init(void) {
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* pthread_once(&g_lib.once, lib_setup);
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* }
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*
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* void lib(void) {
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* lib_init();
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* lib_lock();
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* // do stuff...
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* lib_unlock();
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* }
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*
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* This won't actually aspect fork() until pthread_create() is called,
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* since we don't want normal non-threaded programs to have to acquire
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* exclusive locks on every resource in the entire app just to fork().
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*
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* The vfork() function is *never* aspected. What happens instead is a
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* global variable named `__vforked` is set to true in the child which
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* causes lock functions to do nothing. So far, it works like a charm.
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*
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* @param prepare is run by fork() before forking happens
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* @param parent is run by fork() after forking happens in parent process
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* @param child is run by fork() after forking happens in childe process
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* @return 0 on success, or errno on error
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*/
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int pthread_atfork(atfork_f prepare, atfork_f parent, atfork_f child) {
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if (_weaken(_pthread_atfork)) {
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return _weaken(_pthread_atfork)(prepare, parent, child);
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} else {
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return 0;
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}
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}
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