mirror of
https://github.com/jart/cosmopolitan.git
synced 2025-01-31 03:27:39 +00:00
0b3c81dd4e
This change makes fork() go nearly as fast as sys_fork() on UNIX. As for Windows this change shaves about 4-5ms off fork() + wait() latency. This is accomplished by using WriteProcessMemory() from the parent process to setup the address space of a suspended process; it is better than a pipe
81 lines
3.5 KiB
C
81 lines
3.5 KiB
C
/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
|
|
│ vi: set et ft=c ts=8 sts=2 sw=2 fenc=utf-8 :vi │
|
|
╞══════════════════════════════════════════════════════════════════════════════╡
|
|
│ Copyright 2020 Justine Alexandra Roberts Tunney │
|
|
│ │
|
|
│ Permission to use, copy, modify, and/or distribute this software for │
|
|
│ any purpose with or without fee is hereby granted, provided that the │
|
|
│ above copyright notice and this permission notice appear in all copies. │
|
|
│ │
|
|
│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL │
|
|
│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED │
|
|
│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE │
|
|
│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL │
|
|
│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR │
|
|
│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER │
|
|
│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR │
|
|
│ PERFORMANCE OF THIS SOFTWARE. │
|
|
╚─────────────────────────────────────────────────────────────────────────────*/
|
|
#include "libc/intrin/getauxval.h"
|
|
#include "libc/nexgen32e/rdtsc.h"
|
|
#include "libc/runtime/internal.h"
|
|
#include "libc/runtime/runtime.h"
|
|
#include "libc/str/str.h"
|
|
#include "libc/sysv/consts/auxv.h"
|
|
#include "libc/thread/posixthread.internal.h"
|
|
#include "libc/thread/thread.h"
|
|
#include "libc/thread/tls.h"
|
|
|
|
static int _rand64_pid;
|
|
static unsigned __int128 _rand64_pool;
|
|
static pthread_mutex_t __rand64_lock_obj = PTHREAD_MUTEX_INITIALIZER;
|
|
|
|
void __rand64_lock(void) {
|
|
_pthread_mutex_lock(&__rand64_lock_obj);
|
|
}
|
|
|
|
void __rand64_unlock(void) {
|
|
_pthread_mutex_unlock(&__rand64_lock_obj);
|
|
}
|
|
|
|
void __rand64_wipe(void) {
|
|
_pthread_mutex_wipe_np(&__rand64_lock_obj);
|
|
}
|
|
|
|
/**
|
|
* Returns nondeterministic random data.
|
|
*
|
|
* This function is similar to lemur64() except that it doesn't produce
|
|
* the same sequences of numbers each time your program is run. This is
|
|
* the case even across forks and threads, whose sequences will differ.
|
|
*
|
|
* @see rdseed(), rdrand(), rand(), random(), rngset()
|
|
* @note this function passes bigcrush and practrand
|
|
*/
|
|
uint64_t _rand64(void) {
|
|
void *p;
|
|
uint128_t s;
|
|
__rand64_lock();
|
|
if (__pid == _rand64_pid) {
|
|
s = _rand64_pool; // normal path
|
|
} else {
|
|
if (!_rand64_pid) {
|
|
if (AT_RANDOM && (p = (void *)__getauxval(AT_RANDOM).value)) {
|
|
// linux / freebsd kernel supplied entropy
|
|
memcpy(&s, p, 16);
|
|
} else {
|
|
// otherwise initialize w/ cheap timestamp
|
|
s = kStartTsc;
|
|
}
|
|
} else {
|
|
// blend another timestamp on fork contention
|
|
s = _rand64_pool ^ rdtsc();
|
|
}
|
|
// blend the pid on startup and fork contention
|
|
s ^= __pid;
|
|
_rand64_pid = __pid;
|
|
}
|
|
_rand64_pool = (s *= 15750249268501108917ull); // lemur64
|
|
__rand64_unlock();
|
|
return s >> 64;
|
|
}
|