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/*
* Copyright (C) 2019 Igalia, S.L.
* Copyright (C) 2019 Metrological Group B.V.
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Library General Public
* License as published by the Free Software Foundation; either
* version 2 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Library General Public License for more details.
*
* You should have received a copy of the GNU Library General Public License
* aint with this library; see the file COPYING.LIB. If not, write to
* the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
* Boston, MA 02110-1301, USA.
*/
#pragma once
#include <wtf/Lock.h>
#include <wtf/Threading.h>
namespace WTF {
// By default invalid access checks are only done in Debug builds.
#if !defined(ENABLE_DATA_MUTEX_CHECKS)
#if defined(NDEBUG)
#define ENABLE_DATA_MUTEX_CHECKS 0
#else
#define ENABLE_DATA_MUTEX_CHECKS 1
#endif
#endif
#if ENABLE_DATA_MUTEX_CHECKS
#define DATA_MUTEX_CHECK(expr) RELEASE_ASSERT(expr)
#else
#define DATA_MUTEX_CHECK(expr)
#endif
template <typename T> class DataMutexLocker;
template<typename T>
class DataMutex {
WTF_MAKE_FAST_ALLOCATED;
WTF_MAKE_NONCOPYABLE(DataMutex);
public:
template<typename ...Args>
explicit DataMutex(Args&&... args)
: m_data(std::forward<Args>(args)...)
{ }
private:
friend class DataMutexLocker<T>;
Lock m_mutex;
T m_data WTF_GUARDED_BY_LOCK(m_mutex);
#if ENABLE_DATA_MUTEX_CHECKS
Thread* m_currentMutexHolder { nullptr };
#endif
};
template <typename T>
class WTF_CAPABILITY_SCOPED_LOCK DataMutexLocker {
public:
explicit DataMutexLocker(DataMutex<T>& dataMutex) WTF_ACQUIRES_LOCK(m_dataMutex.m_mutex)
: m_dataMutex(dataMutex)
{
lock();
}
~DataMutexLocker() WTF_RELEASES_LOCK()
{
if (m_isLocked) {
unlock();
}
}
T* operator->()
{
DATA_MUTEX_CHECK(m_isLocked && mutex().isHeld());
assertIsHeld(m_dataMutex.m_mutex);
return &m_dataMutex.m_data;
}
T& operator*()
{
DATA_MUTEX_CHECK(m_isLocked && mutex().isHeld());
assertIsHeld(m_dataMutex.m_mutex);
return m_dataMutex.m_data;
}
Lock& mutex() WTF_RETURNS_LOCK(m_dataMutex.m_mutex)
{
return m_dataMutex.m_mutex;
}
// Note: DataMutexLocker shouldn't be used after this. Due to limitations of clang thread safety analysis this can't
// currently be staticly checked (adding WTF_REQUIRES_LOCK() to operator->() doesn't work.)
// Run-time checks are still performed if enabled.
void unlockEarly() WTF_RELEASES_LOCK(m_dataMutex.m_mutex)
{
assertIsHeld(m_dataMutex.m_mutex);
unlock();
}
// Used to avoid excessive brace scoping when only small parts of the code need to be run unlocked.
// Please be mindful that accessing the wrapped data from the callback is unsafe and will fail on assertions.
// It's helpful to use a minimal lambda capture to be conscious of what data you're having access to in these sections.
void runUnlocked(NOESCAPE const Function<void()>& callback) WTF_IGNORES_THREAD_SAFETY_ANALYSIS
{
unlock();
callback();
lock();
}
private:
DataMutex<T>& m_dataMutex;
bool m_isLocked { false };
void lock() WTF_ACQUIRES_LOCK(m_dataMutex.m_mutex)
{
DATA_MUTEX_CHECK(m_dataMutex.m_currentMutexHolder != &Thread::current()); // Thread attempted recursive lock on non-recursive lock.
mutex().lock();
m_isLocked = true;
#if ENABLE_DATA_MUTEX_CHECKS
m_dataMutex.m_currentMutexHolder = &Thread::current();
#endif
}
void unlock() WTF_RELEASES_LOCK(m_dataMutex.m_mutex)
{
DATA_MUTEX_CHECK(mutex().isHeld());
assertIsHeld(m_dataMutex.m_mutex);
#if ENABLE_DATA_MUTEX_CHECKS
m_dataMutex.m_currentMutexHolder = nullptr;
#endif
m_isLocked = false;
mutex().unlock();
}
};
} // namespace WTF
using WTF::DataMutex;
using WTF::DataMutexLocker;
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