mirror of
https://github.com/jart/cosmopolitan.git
synced 2025-04-14 19:58:46 +00:00
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.
99 lines
4.3 KiB
C
99 lines
4.3 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 2023 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/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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* Attempts acquiring lock.
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*
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* Unlike pthread_mutex_lock() this function won't block and instead
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* returns an error immediately if the lock couldn't be acquired.
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*
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* @return 0 if lock was acquired, otherwise an errno
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* @raise EAGAIN if maximum number of recursive locks is held
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* @raise EBUSY if lock is currently held in read or write mode
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* @raise EINVAL if `mutex` doesn't refer to an initialized lock
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* @raise EDEADLK if `mutex` is `PTHREAD_MUTEX_ERRORCHECK` and the
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* current thread already holds this mutex
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*/
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errno_t pthread_mutex_trylock(pthread_mutex_t *mutex) {
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int me;
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uint64_t word, lock;
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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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// delegate to *NSYNC 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_trylock)) {
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if (_weaken(nsync_mu_trylock)((nsync_mu *)mutex)) {
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return 0;
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} else {
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return EBUSY;
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}
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}
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// handle normal mutexes
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if (MUTEX_TYPE(word) == PTHREAD_MUTEX_NORMAL) {
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word = MUTEX_UNLOCK(word);
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lock = MUTEX_LOCK(word);
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if (atomic_compare_exchange_weak_explicit(&mutex->_word, &word, lock,
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memory_order_acquire,
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memory_order_relaxed))
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return 0;
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return EBUSY;
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}
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// handle recursive and error check mutexes
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me = gettid();
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for (;;) {
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if (MUTEX_OWNER(word) == me) {
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if (MUTEX_TYPE(word) != PTHREAD_MUTEX_ERRORCHECK) {
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if (MUTEX_DEPTH(word) < MUTEX_DEPTH_MAX) {
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if (atomic_compare_exchange_weak_explicit(
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&mutex->_word, &word, MUTEX_INC_DEPTH(word),
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memory_order_relaxed, memory_order_relaxed))
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return 0;
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continue;
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} else {
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return EAGAIN;
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}
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} else {
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return EDEADLK;
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}
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}
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word = MUTEX_UNLOCK(word);
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lock = MUTEX_LOCK(word);
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lock = MUTEX_SET_OWNER(lock, me);
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if (atomic_compare_exchange_weak_explicit(&mutex->_word, &word, lock,
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memory_order_acquire,
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memory_order_relaxed)) {
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mutex->_pid = __pid;
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return 0;
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}
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return EBUSY;
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}
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}
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