mirror of
https://github.com/jart/cosmopolitan.git
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3f0bcdc3ef
- Exhaustively document cancellation points - Rename SIGCANCEL to SIGTHR just like BSDs - Further improve POSIX thread cancellations - Ensure asynchronous cancellations work correctly - Elevate the quality of getrandom() and getentropy() - Make futexes cancel correctly on OpenBSD 6.x and 7.x - Add reboot.com and shutdown.com to examples directory - Remove underscore prefix from awesome timespec_*() APIs - Create assertions that help verify our cancellation points - Remove bad timespec APIs (cmp generalizes eq/ne/gt/gte/lt/lte)
50 lines
2.8 KiB
C
50 lines
2.8 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/calls/cp.internal.h"
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#include "libc/dce.h"
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#include "libc/errno.h"
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#include "libc/intrin/atomic.h"
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#include "libc/thread/wait0.internal.h"
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#include "third_party/nsync/futex.internal.h"
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/**
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* Blocks until memory location becomes zero.
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*
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* This is intended to be used on the child thread id, which is updated
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* by the clone() system call when a thread terminates. We need this in
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* order to know when it's safe to free a thread's stack. This function
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* uses futexes on Linux, FreeBSD, OpenBSD, and Windows. On other
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* platforms this uses polling with exponential backoff.
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*
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* @return 0 on success, or errno on error
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* @raise ECANCELED if calling thread was cancelled in masked mode
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* @cancellationpoint
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*/
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errno_t _wait0(const atomic_int *ctid) {
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int x, rc = 0;
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BEGIN_CANCELLATION_POINT;
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while ((x = atomic_load_explicit(ctid, memory_order_acquire))) {
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if (nsync_futex_wait_(ctid, x, !IsWindows(), 0) == -ECANCELED) {
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rc = ECANCELED;
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break;
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}
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}
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END_CANCELLATION_POINT;
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return rc;
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}
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