mirror of
https://github.com/jart/cosmopolitan.git
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60 lines
3.2 KiB
C
60 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/intrin/pthread.h"
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/**
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* Acquires spin lock.
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*
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* spin l: 181,570c 58,646ns
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* mutex normal l: 297,965c 96,241ns
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* mutex recursive l: 1,112,166c 359,223ns
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* mutex errorcheck l: 1,449,723c 468,252ns
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*
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* If the lock is already held, this function will wait for it to become
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* available. No genuine error conditions are currently defined. This is
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* similar to pthread_mutex_lock() except spin locks are much simpler so
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* this API is able to offer a performance advantage in situations where
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* scalable contention handling isn't necessary. Spinlocks are also very
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* small especially in MODE=tiny where a lock needs 16 bytes of code and
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* unlocking needs just 5 bytes. The lock object also only takes 1 byte.
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*
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* The posixly correct way to use this API is as follows:
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*
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* pthread_spinlock_t lock;
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* pthread_spin_init(&lock, PTHREAD_PROCESS_PRIVATE);
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* pthread_spin_lock(&lock);
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* // do work...
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* pthread_spin_unlock(&lock);
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* pthread_spin_destroy(&lock);
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*
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* Cosmopolitan permits succinct notation for spin locks:
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*
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* pthread_spinlock_t lock = 0;
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* pthread_spin_lock(&lock);
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* // do work...
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* pthread_spin_unlock(&lock);
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*
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* @return 0 on success, or errno on error
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* @see pthread_spin_trylock
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* @see pthread_spin_unlock
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* @see pthread_spin_init
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*/
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int(pthread_spin_lock)(pthread_spinlock_t *spin) {
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return pthread_spin_lock(spin);
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}
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