mirror of
https://github.com/jart/cosmopolitan.git
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464858dbb4
This fixes a regression in mmap(MAP_FIXED) on Windows caused by a recent revision. This change also fixes ZipOS so it no longer needs a MAP_FIXED mapping to open files from the PKZIP store. The memory mapping mutex was implemented incorrectly earlier which meant that ftrace and strace could cause cause crashes. This lock and other recursive mutexes are rewritten so that it should be provable that recursive mutexes in cosmopolitan are asynchronous signal safe.
87 lines
3.9 KiB
C
87 lines
3.9 KiB
C
/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
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│ vi: set et 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/calls.h"
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#include "libc/errno.h"
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#include "libc/intrin/atomic.h"
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#include "libc/intrin/strace.internal.h"
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#include "libc/intrin/weaken.h"
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#include "libc/runtime/internal.h"
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#include "libc/thread/lock.h"
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#include "libc/thread/thread.h"
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#include "third_party/nsync/mu.h"
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/**
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* Releases mutex.
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*
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* This function does nothing in vfork() children.
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*
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* @return 0 on success or error number on failure
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* @raises EPERM if in error check mode and not owned by caller
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* @vforksafe
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*/
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errno_t pthread_mutex_unlock(pthread_mutex_t *mutex) {
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int me;
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uint64_t word, lock;
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LOCKTRACE("pthread_mutex_unlock(%t)", mutex);
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// get current state of lock
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word = atomic_load_explicit(&mutex->_word, memory_order_relaxed);
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// use fancy nsync mutex if possible
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if (MUTEX_TYPE(word) == PTHREAD_MUTEX_NORMAL && //
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MUTEX_PSHARED(word) == PTHREAD_PROCESS_PRIVATE && //
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_weaken(nsync_mu_unlock)) {
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_weaken(nsync_mu_unlock)((nsync_mu *)mutex);
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return 0;
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}
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// implement barebones normal mutexes
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if (MUTEX_TYPE(word) == PTHREAD_MUTEX_NORMAL) {
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lock = MUTEX_UNLOCK(word);
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atomic_store_explicit(&mutex->_word, lock, memory_order_release);
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return 0;
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}
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// implement recursive mutex unlocking
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me = gettid();
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for (;;) {
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// we allow unlocking an initialized lock that wasn't locked, but we
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// don't allow unlocking a lock held by another thread, or unlocking
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// recursive locks from a forked child, since it should be re-init'd
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if (MUTEX_OWNER(word) && (MUTEX_OWNER(word) != me || mutex->_pid != __pid))
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return EPERM;
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// check if this is a nested lock with signal safety
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if (MUTEX_DEPTH(word)) {
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if (atomic_compare_exchange_weak_explicit(
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&mutex->_word, &word, MUTEX_DEC_DEPTH(word), memory_order_relaxed,
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memory_order_relaxed))
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return 0;
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continue;
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}
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// actually unlock the mutex
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if (atomic_compare_exchange_weak_explicit(
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&mutex->_word, &word, MUTEX_UNLOCK(word), memory_order_release,
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memory_order_relaxed))
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return 0;
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}
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}
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