mirror of
https://github.com/jart/cosmopolitan.git
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74 lines
3.7 KiB
C
74 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/calls/calls.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/futex.internal.h"
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#include "libc/intrin/intrin.h"
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#include "libc/intrin/kprintf.h"
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#include "libc/intrin/pthread.h"
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#include "libc/limits.h"
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/**
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* Waits for all threads to arrive at barrier.
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*
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* When the barrier is broken, the state becomes reset to what it was
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* when pthread_barrier_init() was called, so that the barrior may be
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* used again in the same way. The last thread to arrive shall be the
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* last to leave and it returns a magic value.
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*
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* @return 0 on success, `PTHREAD_BARRIER_SERIAL_THREAD` to one lucky
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* thread which was the last arrival, or an errno on error
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*/
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int pthread_barrier_wait(pthread_barrier_t *barrier) {
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if (atomic_fetch_add(&barrier->waits, 1) + 1 == barrier->count) {
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if (atomic_fetch_add(&barrier->waits, 1) + 1 < barrier->count * 2) {
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atomic_store(&barrier->popped, 1);
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do {
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if (IsLinux() || IsOpenbsd()) {
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if (barrier->attr == PTHREAD_PROCESS_SHARED) {
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_futex_wake_public(&barrier->popped, INT_MAX);
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} else {
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_futex_wake_private(&barrier->popped, INT_MAX);
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}
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} else {
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pthread_yield();
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}
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} while (atomic_load_explicit(&barrier->waits, memory_order_relaxed) <
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barrier->count * 2);
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atomic_store_explicit(&barrier->popped, 0, memory_order_relaxed);
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}
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atomic_store_explicit(&barrier->waits, 0, memory_order_relaxed);
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return PTHREAD_BARRIER_SERIAL_THREAD;
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}
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do {
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if (IsLinux() || IsOpenbsd()) {
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if (barrier->attr == PTHREAD_PROCESS_SHARED) {
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_futex_wait_public(&barrier->popped, 0, 0);
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} else {
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_futex_wait_private(&barrier->popped, 0, 0);
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}
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} else {
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pthread_yield();
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}
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} while (atomic_load_explicit(&barrier->waits, memory_order_relaxed) <
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barrier->count);
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atomic_fetch_add(&barrier->waits, 1);
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return 0;
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}
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