mirror of
https://github.com/jart/cosmopolitan.git
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187 lines
7 KiB
C
187 lines
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 et ft=c ts=2 sts=2 sw=2 fenc=utf-8 :vi │
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╞══════════════════════════════════════════════════════════════════════════════╡
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│ Copyright 2020 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/assert.h"
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#include "libc/atomic.h"
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#include "libc/calls/calls.h"
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#include "libc/calls/state.internal.h"
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#include "libc/calls/struct/sigset.h"
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#include "libc/calls/struct/sigset.internal.h"
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#include "libc/calls/struct/timespec.h"
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#include "libc/calls/syscall-nt.internal.h"
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#include "libc/calls/syscall-sysv.internal.h"
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#include "libc/dce.h"
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#include "libc/intrin/atomic.h"
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#include "libc/intrin/dll.h"
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#include "libc/intrin/kprintf.h"
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#include "libc/intrin/maps.h"
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#include "libc/intrin/strace.h"
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#include "libc/intrin/weaken.h"
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#include "libc/nt/files.h"
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#include "libc/nt/process.h"
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#include "libc/nt/runtime.h"
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#include "libc/nt/synchronization.h"
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#include "libc/nt/thread.h"
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#include "libc/proc/proc.internal.h"
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#include "libc/runtime/internal.h"
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#include "libc/runtime/memtrack.internal.h"
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#include "libc/runtime/runtime.h"
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#include "libc/runtime/syslib.internal.h"
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#include "libc/sysv/consts/sig.h"
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#include "libc/thread/posixthread.internal.h"
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#include "libc/thread/tls.h"
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__static_yoink("_pthread_atfork");
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extern pthread_mutex_t _rand64_lock_obj;
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extern pthread_mutex_t _pthread_lock_obj;
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// fork needs to lock every lock, which makes it very single-threaded in
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// nature. the outermost lock matters the most because it serializes all
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// threads attempting to spawn processes. the outer lock can't be a spin
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// lock that a pthread_atfork() caller slipped in. to ensure it's a fair
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// lock, we add an additional one of our own, which protects other locks
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static pthread_mutex_t _fork_gil = PTHREAD_MUTEX_INITIALIZER;
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static void _onfork_prepare(void) {
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if (_weaken(_pthread_onfork_prepare))
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_weaken(_pthread_onfork_prepare)();
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if (IsWindows())
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__proc_lock();
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_pthread_lock();
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__maps_lock();
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__fds_lock();
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pthread_mutex_lock(&_rand64_lock_obj);
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LOCKTRACE("READY TO ROCK AND ROLL");
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}
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static void _onfork_parent(void) {
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pthread_mutex_unlock(&_rand64_lock_obj);
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__fds_unlock();
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__maps_unlock();
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_pthread_unlock();
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if (IsWindows())
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__proc_unlock();
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if (_weaken(_pthread_onfork_parent))
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_weaken(_pthread_onfork_parent)();
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}
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static void _onfork_child(void) {
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if (IsWindows())
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__proc_wipe();
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__fds_lock_obj = (pthread_mutex_t)PTHREAD_RECURSIVE_MUTEX_INITIALIZER_NP;
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_rand64_lock_obj = (pthread_mutex_t)PTHREAD_RECURSIVE_MUTEX_INITIALIZER_NP;
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_pthread_lock_obj = (pthread_mutex_t)PTHREAD_MUTEX_INITIALIZER;
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atomic_store_explicit(&__maps.lock, 0, memory_order_relaxed);
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if (_weaken(_pthread_onfork_child))
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_weaken(_pthread_onfork_child)();
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}
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static int _forker(uint32_t dwCreationFlags) {
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long micros;
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struct Dll *e;
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struct timespec started;
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int ax, dx, tid, parent;
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parent = __pid;
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started = timespec_real();
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_onfork_prepare();
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if (!IsWindows()) {
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ax = sys_fork();
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} else {
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ax = sys_fork_nt(dwCreationFlags);
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}
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micros = timespec_tomicros(timespec_sub(timespec_real(), started));
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if (!ax) {
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// get new process id
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if (!IsWindows()) {
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dx = sys_getpid().ax;
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} else {
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dx = GetCurrentProcessId();
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}
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__pid = dx;
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// turn other threads into zombies
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// we can't free() them since we're monopolizing all locks
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// we assume the operating system already reclaimed system handles
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struct CosmoTib *tib = __get_tls();
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struct PosixThread *pt = (struct PosixThread *)tib->tib_pthread;
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dll_remove(&_pthread_list, &pt->list);
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for (e = dll_first(_pthread_list); e; e = dll_next(_pthread_list, e)) {
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atomic_store_explicit(&POSIXTHREAD_CONTAINER(e)->pt_status,
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kPosixThreadZombie, memory_order_relaxed);
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atomic_store_explicit(&POSIXTHREAD_CONTAINER(e)->tib->tib_syshand, 0,
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memory_order_relaxed);
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}
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dll_make_first(&_pthread_list, &pt->list);
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// get new main thread id
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tid = IsLinux() || IsXnuSilicon() ? dx : sys_gettid();
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atomic_store_explicit(&tib->tib_tid, tid, memory_order_relaxed);
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atomic_store_explicit(&pt->ptid, tid, memory_order_relaxed);
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// get new system thread handle
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intptr_t syshand = 0;
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if (IsXnuSilicon()) {
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syshand = __syslib->__pthread_self();
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} else if (IsWindows()) {
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DuplicateHandle(GetCurrentProcess(), GetCurrentThread(),
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GetCurrentProcess(), &syshand, 0, false,
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kNtDuplicateSameAccess);
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}
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atomic_store_explicit(&tib->tib_syshand, syshand, memory_order_relaxed);
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// we can't be canceled if the canceler no longer exists
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atomic_store_explicit(&pt->pt_canceled, false, memory_order_relaxed);
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// run user fork callbacks
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_onfork_child();
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STRACE("fork() → 0 (child of %d; took %ld us)", parent, micros);
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} else {
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// this is the parent process
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_onfork_parent();
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STRACE("fork() → %d% m (took %ld us)", ax, micros);
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}
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return ax;
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}
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int _fork(uint32_t dwCreationFlags) {
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int rc;
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BLOCK_SIGNALS;
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pthread_mutex_lock(&_fork_gil);
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rc = _forker(dwCreationFlags);
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if (!rc) {
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pthread_mutex_init(&_fork_gil, 0);
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} else {
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pthread_mutex_unlock(&_fork_gil);
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}
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ALLOW_SIGNALS;
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return rc;
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}
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/**
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* Creates new process.
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*
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* @return 0 to child, child pid to parent, or -1 w/ errno
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* @raise EAGAIN if `RLIMIT_NPROC` was exceeded or system lacked resources
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* @raise ENOMEM if we require more vespene gas
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* @asyncsignalsafe
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*/
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int fork(void) {
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return _fork(0);
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}
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