mirror of
https://github.com/jart/cosmopolitan.git
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64 lines
3.2 KiB
C
64 lines
3.2 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/calls/strace.internal.h"
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#include "libc/calls/struct/timespec.h"
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#include "libc/dce.h"
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#include "libc/errno.h"
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#include "libc/intrin/atomic.h"
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#include "libc/intrin/describeflags.internal.h"
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#include "libc/sysv/consts/futex.h"
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#include "libc/thread/thread.h"
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#include "libc/thread/wait0.internal.h"
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int _futex(int *, int, int, const struct timespec *);
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/**
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* Blocks until memory location becomes zero.
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*
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* This is intended to be used on the child thread id, which is updated
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* by the _spawn() system call when a thread terminates. The purpose of
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* this operation is to know when it's safe to munmap() a threads stack
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*/
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void _wait0(const int *ctid) {
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int x, rc;
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char buf[12];
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for (;;) {
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if (!(x = atomic_load_explicit(ctid, memory_order_relaxed))) {
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break;
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} else if (IsLinux() || IsOpenbsd()) {
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rc = _futex(ctid, FUTEX_WAIT, x, &(struct timespec){2});
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STRACE("futex(%t, FUTEX_WAIT, %d, {2, 0}) → %s", ctid, x,
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(DescribeFutexResult)(buf, rc));
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if (IsOpenbsd() && rc > 0) rc = -rc;
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if (!(rc == 0 || //
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rc == -EINTR || //
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rc == -ETIMEDOUT || //
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rc == -EWOULDBLOCK)) {
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notpossible;
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}
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} else {
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pthread_yield();
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}
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}
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if (IsOpenbsd()) {
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// TODO(jart): Why do we need it? It's not even perfect.
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// What's up with all these OpenBSD flakes??
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pthread_yield();
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}
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}
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