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https://github.com/jart/cosmopolitan.git
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7838edae88
The greenbean web server now works nearly perfectly on Windows with over 1000 threads. But some synchronization issues still remain which prevent us from going over nine thousand.
80 lines
3.7 KiB
C
80 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=8 sts=2 sw=2 fenc=utf-8 :vi│
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╞══════════════════════════════════════════════════════════════════════════════╡
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│ Copyright 2020 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/bits.h"
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#include "libc/bits/weaken.h"
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#include "libc/calls/calls.h"
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#include "libc/intrin/spinlock.h"
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#include "libc/nexgen32e/rdtsc.h"
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#include "libc/nt/thread.h"
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#include "libc/rand/rand.h"
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#include "libc/runtime/internal.h"
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#include "libc/runtime/runtime.h"
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#include "libc/sysv/consts/auxv.h"
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#include "libc/thread/create.h"
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static int thepid;
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static uint128_t thepool;
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_Alignas(64) static int rand64_lock;
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/**
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* Returns nondeterministic random data.
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*
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* This function is similar to lemur64() except that it's intended to be
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* unpredictable. This PRNG automatically seeds itself on startup using
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* a much stronger and faster random source than `srand(time(0))`. This
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* function will automatically reseed itself when new processes and
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* threads are spawned. This function is thread safe in the sense that a
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* race condition can't happen where two threads return the same result.
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*
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* @see rdseed(), rdrand(), rand(), random(), rngset()
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* @note this function is not intended for cryptography
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* @note this function passes bigcrush and practrand
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* @note this function takes at minimum 15 cycles
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* @asyncsignalsafe
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* @threadsafe
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* @vforksafe
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*/
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uint64_t rand64(void) {
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void *p;
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uint128_t s;
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_spinlock(&rand64_lock);
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if (__pid == thepid) {
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s = thepool; // normal path
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} else {
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if (!thepid) {
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if (AT_RANDOM && (p = (void *)getauxval(AT_RANDOM))) {
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// linux / freebsd kernel supplied entropy
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memcpy(&s, p, 16);
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} else {
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// otherwise initialize w/ cheap timestamp
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s = kStartTsc;
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}
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} else {
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// blend another timestamp on fork contention
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s = thepool ^ rdtsc();
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}
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// blend the pid on startup and fork contention
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s ^= __pid;
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thepid = __pid;
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}
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thepool = (s *= 15750249268501108917ull); // lemur64
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_spunlock(&rand64_lock);
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return s >> 64;
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}
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