mirror of
https://github.com/jart/cosmopolitan.git
synced 2025-01-31 11:37:35 +00:00
96 lines
4.1 KiB
C
96 lines
4.1 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/assert.h"
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#include "libc/bits/asmflag.h"
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#include "libc/bits/atomic.h"
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#include "libc/calls/calls.h"
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#include "libc/dce.h"
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#include "libc/errno.h"
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#include "libc/intrin/futex.internal.h"
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#include "libc/intrin/pthread.h"
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#include "libc/intrin/spinlock.h"
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#include "libc/linux/futex.h"
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#include "libc/nexgen32e/threaded.h"
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#include "libc/sysv/consts/futex.h"
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#include "libc/sysv/consts/nr.h"
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static int pthread_mutex_lock_spin(pthread_mutex_t *mutex, int expect,
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int tries) {
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if (tries < 7) {
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volatile int i;
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for (i = 0; i != 1 << tries; i++) {
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}
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tries++;
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} else if (IsLinux() || IsOpenbsd()) {
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atomic_fetch_add(&mutex->waits, 1);
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_futex_wait(&mutex->lock, expect, &(struct timespec){1});
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atomic_fetch_sub(&mutex->waits, 1);
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} else {
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sched_yield();
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}
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return tries;
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}
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/**
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* Locks mutex.
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*
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* _spinlock() 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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* @return 0 on success, or error number on failure
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*/
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int(pthread_mutex_lock)(pthread_mutex_t *mutex) {
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int me, owner, tries;
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switch (mutex->attr) {
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case PTHREAD_MUTEX_NORMAL:
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for (tries = 0;;) {
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if (!atomic_load_explicit(&mutex->lock, memory_order_relaxed) &&
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!atomic_exchange_explicit(&mutex->lock, 1, memory_order_acquire)) {
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break;
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}
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tries = pthread_mutex_lock_spin(mutex, 1, tries);
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}
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return 0;
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case PTHREAD_MUTEX_RECURSIVE:
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case PTHREAD_MUTEX_ERRORCHECK:
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for (tries = 0, me = gettid();;) {
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owner = atomic_load_explicit(&mutex->lock, memory_order_relaxed);
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if (!owner && atomic_compare_exchange_weak_explicit(
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&mutex->lock, &owner, me, memory_order_acquire,
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memory_order_relaxed)) {
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break;
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} else if (owner == me) {
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if (mutex->attr != PTHREAD_MUTEX_ERRORCHECK) {
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break;
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} else {
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assert(!"dead lock");
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return EDEADLK;
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}
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}
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tries = pthread_mutex_lock_spin(mutex, owner, tries);
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}
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++mutex->reent;
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return 0;
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default:
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assert(!"inva lock");
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return EINVAL;
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}
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}
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