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48 lines
2.4 KiB
C
48 lines
2.4 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/atomic.h"
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#include "libc/calls/calls.h"
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#include "libc/intrin/pthread.h"
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int pthread_once(pthread_once_t *once, void init(void)) {
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int x;
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unsigned tries;
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switch ((x = atomic_load(once))) {
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case 0:
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if (atomic_compare_exchange_strong(once, &x, 1)) {
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init();
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atomic_store(once, 2);
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break;
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}
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// fallthrough
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case 1:
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tries = 0;
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do {
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if (++tries & 7) {
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__builtin_ia32_pause();
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} else {
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sched_yield();
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}
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} while (atomic_load(once) == 1);
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break;
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default:
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break;
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}
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return 0;
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}
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