149 lines
4.2 KiB
C++
149 lines
4.2 KiB
C++
/*
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* Copyright (C) 2019 Igalia, S.L.
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* Copyright (C) 2019 Metrological Group B.V.
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*
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* This library is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Library General Public
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* License as published by the Free Software Foundation; either
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* version 2 of the License, or (at your option) any later version.
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*
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* This library 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 GNU
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* Library General Public License for more details.
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*
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* You should have received a copy of the GNU Library General Public License
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* aint with this library; see the file COPYING.LIB. If not, write to
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* the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
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* Boston, MA 02110-1301, USA.
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*/
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#pragma once
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#include <wtf/Lock.h>
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#include <wtf/Threading.h>
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namespace WTF {
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// By default invalid access checks are only done in Debug builds.
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#if !defined(ENABLE_DATA_MUTEX_CHECKS)
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#if defined(NDEBUG)
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#define ENABLE_DATA_MUTEX_CHECKS 0
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#else
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#define ENABLE_DATA_MUTEX_CHECKS 1
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#endif
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#endif
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#if ENABLE_DATA_MUTEX_CHECKS
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#define DATA_MUTEX_CHECK(expr) RELEASE_ASSERT(expr)
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#else
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#define DATA_MUTEX_CHECK(expr)
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#endif
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template <typename T> class DataMutexLocker;
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template<typename T>
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class DataMutex {
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WTF_MAKE_FAST_ALLOCATED;
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WTF_MAKE_NONCOPYABLE(DataMutex);
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public:
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template<typename ...Args>
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explicit DataMutex(Args&&... args)
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: m_data(std::forward<Args>(args)...)
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{ }
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private:
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friend class DataMutexLocker<T>;
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Lock m_mutex;
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T m_data WTF_GUARDED_BY_LOCK(m_mutex);
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#if ENABLE_DATA_MUTEX_CHECKS
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Thread* m_currentMutexHolder { nullptr };
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#endif
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};
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template <typename T>
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class WTF_CAPABILITY_SCOPED_LOCK DataMutexLocker {
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public:
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explicit DataMutexLocker(DataMutex<T>& dataMutex) WTF_ACQUIRES_LOCK(m_dataMutex.m_mutex)
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: m_dataMutex(dataMutex)
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{
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lock();
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}
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~DataMutexLocker() WTF_RELEASES_LOCK()
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{
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if (m_isLocked) {
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unlock();
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}
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}
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T* operator->()
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{
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DATA_MUTEX_CHECK(m_isLocked && mutex().isHeld());
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assertIsHeld(m_dataMutex.m_mutex);
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return &m_dataMutex.m_data;
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}
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T& operator*()
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{
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DATA_MUTEX_CHECK(m_isLocked && mutex().isHeld());
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assertIsHeld(m_dataMutex.m_mutex);
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return m_dataMutex.m_data;
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}
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Lock& mutex() WTF_RETURNS_LOCK(m_dataMutex.m_mutex)
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{
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return m_dataMutex.m_mutex;
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}
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// Note: DataMutexLocker shouldn't be used after this. Due to limitations of clang thread safety analysis this can't
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// currently be staticly checked (adding WTF_REQUIRES_LOCK() to operator->() doesn't work.)
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// Run-time checks are still performed if enabled.
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void unlockEarly() WTF_RELEASES_LOCK(m_dataMutex.m_mutex)
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{
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assertIsHeld(m_dataMutex.m_mutex);
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unlock();
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}
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// Used to avoid excessive brace scoping when only small parts of the code need to be run unlocked.
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// Please be mindful that accessing the wrapped data from the callback is unsafe and will fail on assertions.
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// It's helpful to use a minimal lambda capture to be conscious of what data you're having access to in these sections.
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void runUnlocked(const Function<void()>& callback) WTF_IGNORES_THREAD_SAFETY_ANALYSIS
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{
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unlock();
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callback();
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lock();
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}
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private:
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DataMutex<T>& m_dataMutex;
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bool m_isLocked { false };
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void lock() WTF_ACQUIRES_LOCK(m_dataMutex.m_mutex)
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{
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DATA_MUTEX_CHECK(m_dataMutex.m_currentMutexHolder != &Thread::current()); // Thread attempted recursive lock on non-recursive lock.
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mutex().lock();
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m_isLocked = true;
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#if ENABLE_DATA_MUTEX_CHECKS
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m_dataMutex.m_currentMutexHolder = &Thread::current();
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#endif
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}
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void unlock() WTF_RELEASES_LOCK(m_dataMutex.m_mutex)
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{
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DATA_MUTEX_CHECK(mutex().isHeld());
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assertIsHeld(m_dataMutex.m_mutex);
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#if ENABLE_DATA_MUTEX_CHECKS
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m_dataMutex.m_currentMutexHolder = nullptr;
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#endif
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m_isLocked = false;
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mutex().unlock();
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}
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};
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} // namespace WTF
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using WTF::DataMutex;
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using WTF::DataMutexLocker;
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