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Use *NSYNC for POSIX threads locking APIs

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Condition variables, barriers, and r/w locks now work very well.
This commit is contained in:
Justine Tunney 2022-09-11 11:02:07 -07:00
parent 3de35e196c
commit b5cb71ab84
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GPG key ID: BE714B4575D6E328
197 changed files with 3734 additions and 3817 deletions
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64
libc/thread/wait0.c Normal file
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/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8 :vi│
╞══════════════════════════════════════════════════════════════════════════════╡
│ Copyright 2022 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/calls/strace.internal.h"
#include "libc/calls/struct/timespec.h"
#include "libc/dce.h"
#include "libc/errno.h"
#include "libc/intrin/atomic.h"
#include "libc/intrin/describeflags.internal.h"
#include "libc/sysv/consts/futex.h"
#include "libc/thread/thread.h"
#include "libc/thread/wait0.internal.h"
int _futex(int *, int, int, const struct timespec *);
/**
* Blocks until memory location becomes zero.
*
* This is intended to be used on the child thread id, which is updated
* by the _spawn() system call when a thread terminates. The purpose of
* this operation is to know when it's safe to munmap() a threads stack
*/
void _wait0(const int *ctid) {
int x, rc;
char buf[12];
for (;;) {
if (!(x = atomic_load_explicit(ctid, memory_order_relaxed))) {
break;
} else if (IsLinux() || IsOpenbsd()) {
rc = _futex(ctid, FUTEX_WAIT, x, &(struct timespec){2});
STRACE("futex(%t, FUTEX_WAIT, %d, {2, 0}) → %s", ctid, x,
(DescribeFutexResult)(buf, rc));
if (IsOpenbsd() && rc > 0) rc = -rc;
if (!(rc == 0 || //
rc == -EINTR || //
rc == -ETIMEDOUT || //
rc == -EWOULDBLOCK)) {
notpossible;
}
} else {
pthread_yield();
}
}
if (IsOpenbsd()) {
// TODO(jart): Why do we need it? It's not even perfect.
// What's up with all these OpenBSD flakes??
pthread_yield();
}
}