122 lines
3.1 KiB
C++
122 lines
3.1 KiB
C++
/*
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* DISTRHO Cardinal Plugin
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* Copyright (C) 2021-2022 Filipe Coelho <falktx@falktx.com>
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License as
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* published by the Free Software Foundation; either version 3 of
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* the License, or any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* For a full copy of the GNU General Public License see the LICENSE file.
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*/
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#pragma once
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#include <pthread.h>
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#ifdef __MOD_DEVICES__
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#include <linux/futex.h>
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#include <sys/time.h>
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#include <errno.h>
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#include <syscall.h>
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#include <unistd.h>
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#endif
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/* replace Rack's mutex with our own custom one, which can do priority inversion. */
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namespace rack {
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struct SharedMutex {
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pthread_mutex_t readLock;
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#ifdef __MOD_DEVICES__
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int writeLock;
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#else
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pthread_mutex_t writeLock;
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#endif
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SharedMutex() noexcept {
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pthread_mutexattr_t attr;
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pthread_mutexattr_init(&attr);
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pthread_mutexattr_setprotocol(&attr, PTHREAD_PRIO_INHERIT);
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pthread_mutexattr_settype(&attr, PTHREAD_MUTEX_RECURSIVE);
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pthread_mutex_init(&readLock, &attr);
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pthread_mutexattr_destroy(&attr);
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#ifdef __MOD_DEVICES__
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writeLock = 1;
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#else
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pthread_mutexattr_t attr2;
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pthread_mutexattr_init(&attr2);
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pthread_mutexattr_setprotocol(&attr2, PTHREAD_PRIO_NONE);
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pthread_mutexattr_settype(&attr2, PTHREAD_MUTEX_NORMAL);
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pthread_mutex_init(&writeLock, &attr2);
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pthread_mutexattr_destroy(&attr2);
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#endif
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}
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~SharedMutex() noexcept {
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pthread_mutex_destroy(&readLock);
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#ifndef __MOD_DEVICES__
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pthread_mutex_destroy(&writeLock);
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#endif
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}
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// for std::lock_guard usage, writers lock
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void lock() noexcept {
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#ifdef __MOD_DEVICES__
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for (;;)
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{
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if (__sync_bool_compare_and_swap(&writeLock, 1, 0))
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return;
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if (syscall(__NR_futex, &writeLock, FUTEX_WAIT_PRIVATE, 0, nullptr, nullptr, 0) != 0)
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{
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if (errno != EAGAIN && errno != EINTR)
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return;
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}
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}
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#else
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pthread_mutex_lock(&writeLock);
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#endif
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pthread_mutex_lock(&readLock);
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}
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void unlock() noexcept {
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pthread_mutex_unlock(&readLock);
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#ifdef __MOD_DEVICES__
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if (__sync_bool_compare_and_swap(&writeLock, 0, 1))
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syscall(__NR_futex, &writeLock, FUTEX_WAKE_PRIVATE, 1, nullptr, nullptr, 0);
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#else
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pthread_mutex_unlock(&writeLock);
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#endif
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}
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// for SharedLock usage, readers lock
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void lock_shared() noexcept {
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pthread_mutex_lock(&readLock);
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}
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void unlock_shared() noexcept {
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pthread_mutex_unlock(&readLock);
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}
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};
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template <class Mutex>
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struct SharedLock {
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Mutex& mutex;
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SharedLock(Mutex& m) noexcept : mutex(m) {
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mutex.lock_shared();
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}
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~SharedLock() noexcept {
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mutex.unlock_shared();
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}
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};
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} // namespace rack
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