/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│ │ vi: set et ft=c ts=2 sts=2 sw=2 fenc=utf-8 :vi │ ╞══════════════════════════════════════════════════════════════════════════════╡ │ Copyright 2020 Justine Alexandra Roberts Tunney │ │ │ │ Permission to use, copy, modify, and/or distribute this software for │ │ any purpose with or without fee is hereby granted, provided that the │ │ above copyright notice and this permission notice appear in all copies. │ │ │ │ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL │ │ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED │ │ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE │ │ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL │ │ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR │ │ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER │ │ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR │ │ PERFORMANCE OF THIS SOFTWARE. │ ╚─────────────────────────────────────────────────────────────────────────────*/ #include "libc/assert.h" #include "libc/atomic.h" #include "libc/calls/calls.h" #include "libc/calls/state.internal.h" #include "libc/calls/struct/sigset.h" #include "libc/calls/struct/sigset.internal.h" #include "libc/calls/struct/timespec.h" #include "libc/calls/syscall-nt.internal.h" #include "libc/calls/syscall-sysv.internal.h" #include "libc/dce.h" #include "libc/intrin/atomic.h" #include "libc/intrin/dll.h" #include "libc/intrin/kprintf.h" #include "libc/intrin/maps.h" #include "libc/intrin/strace.h" #include "libc/intrin/weaken.h" #include "libc/nt/files.h" #include "libc/nt/process.h" #include "libc/nt/runtime.h" #include "libc/nt/synchronization.h" #include "libc/nt/thread.h" #include "libc/proc/proc.internal.h" #include "libc/runtime/internal.h" #include "libc/runtime/memtrack.internal.h" #include "libc/runtime/runtime.h" #include "libc/runtime/syslib.internal.h" #include "libc/sysv/consts/sig.h" #include "libc/thread/posixthread.internal.h" #include "libc/thread/tls.h" __static_yoink("_pthread_atfork"); extern pthread_mutex_t _rand64_lock_obj; extern pthread_mutex_t _pthread_lock_obj; // fork needs to lock every lock, which makes it very single-threaded in // nature. the outermost lock matters the most because it serializes all // threads attempting to spawn processes. the outer lock can't be a spin // lock that a pthread_atfork() caller slipped in. to ensure it's a fair // lock, we add an additional one of our own, which protects other locks static pthread_mutex_t _fork_gil = PTHREAD_MUTEX_INITIALIZER; static void _onfork_prepare(void) { if (_weaken(_pthread_onfork_prepare)) _weaken(_pthread_onfork_prepare)(); if (IsWindows()) __proc_lock(); _pthread_lock(); __maps_lock(); __fds_lock(); pthread_mutex_lock(&_rand64_lock_obj); LOCKTRACE("READY TO ROCK AND ROLL"); } static void _onfork_parent(void) { pthread_mutex_unlock(&_rand64_lock_obj); __fds_unlock(); __maps_unlock(); _pthread_unlock(); if (IsWindows()) __proc_unlock(); if (_weaken(_pthread_onfork_parent)) _weaken(_pthread_onfork_parent)(); } static void _onfork_child(void) { if (IsWindows()) __proc_wipe(); __fds_lock_obj = (pthread_mutex_t)PTHREAD_RECURSIVE_MUTEX_INITIALIZER_NP; _rand64_lock_obj = (pthread_mutex_t)PTHREAD_RECURSIVE_MUTEX_INITIALIZER_NP; _pthread_lock_obj = (pthread_mutex_t)PTHREAD_RECURSIVE_MUTEX_INITIALIZER_NP; atomic_store_explicit(&__maps.lock, 0, memory_order_relaxed); if (_weaken(_pthread_onfork_child)) _weaken(_pthread_onfork_child)(); } static int _forker(uint32_t dwCreationFlags) { long micros; struct Dll *e; struct timespec started; int ax, dx, tid, parent; parent = __pid; started = timespec_real(); _onfork_prepare(); if (!IsWindows()) { ax = sys_fork(); } else { ax = sys_fork_nt(dwCreationFlags); } micros = timespec_tomicros(timespec_sub(timespec_real(), started)); if (!ax) { // get new process id if (!IsWindows()) { dx = sys_getpid().ax; } else { dx = GetCurrentProcessId(); } __pid = dx; // turn other threads into zombies // we can't free() them since we're monopolizing all locks // we assume the operating system already reclaimed system handles struct CosmoTib *tib = __get_tls(); struct PosixThread *pt = (struct PosixThread *)tib->tib_pthread; dll_remove(&_pthread_list, &pt->list); for (e = dll_first(_pthread_list); e; e = dll_next(_pthread_list, e)) { atomic_store_explicit(&POSIXTHREAD_CONTAINER(e)->pt_status, kPosixThreadZombie, memory_order_relaxed); atomic_store_explicit(&POSIXTHREAD_CONTAINER(e)->tib->tib_syshand, 0, memory_order_relaxed); } dll_make_first(&_pthread_list, &pt->list); // get new main thread id tid = IsLinux() || IsXnuSilicon() ? dx : sys_gettid(); atomic_store_explicit(&tib->tib_tid, tid, memory_order_relaxed); atomic_store_explicit(&pt->ptid, tid, memory_order_relaxed); // get new system thread handle intptr_t syshand = 0; if (IsXnuSilicon()) { syshand = __syslib->__pthread_self(); } else if (IsWindows()) { DuplicateHandle(GetCurrentProcess(), GetCurrentThread(), GetCurrentProcess(), &syshand, 0, false, kNtDuplicateSameAccess); } atomic_store_explicit(&tib->tib_syshand, syshand, memory_order_relaxed); // we can't be canceled if the canceler no longer exists atomic_store_explicit(&pt->pt_canceled, false, memory_order_relaxed); // run user fork callbacks _onfork_child(); STRACE("fork() → 0 (child of %d; took %ld us)", parent, micros); } else { // this is the parent process _onfork_parent(); STRACE("fork() → %d% m (took %ld us)", ax, micros); } return ax; } int _fork(uint32_t dwCreationFlags) { int rc; BLOCK_SIGNALS; pthread_mutex_lock(&_fork_gil); rc = _forker(dwCreationFlags); if (!rc) { pthread_mutex_init(&_fork_gil, 0); } else { pthread_mutex_unlock(&_fork_gil); } ALLOW_SIGNALS; return rc; } /** * Creates new process. * * @return 0 to child, child pid to parent, or -1 w/ errno * @raise EAGAIN if `RLIMIT_NPROC` was exceeded or system lacked resources * @raise ENOMEM if we require more vespene gas * @asyncsignalsafe */ int fork(void) { return _fork(0); }