#pragma once
#include <wtf/Assertions.h>
#include <wtf/Atomics.h>
#include <wtf/Compiler.h>
#include <wtf/ForbidHeapAllocation.h>
#include <wtf/Noncopyable.h>
#include <wtf/ThreadSanitizerSupport.h>
namespace WTF {
enum NoLockingNecessaryTag { NoLockingNecessary };
class AbstractLocker {
WTF_MAKE_NONCOPYABLE(AbstractLocker);
public:
AbstractLocker(NoLockingNecessaryTag)
{
}
protected:
AbstractLocker()
{
}
};
template<typename T> class DropLockForScope;
template<typename T>
class Locker : public AbstractLocker {
public:
explicit Locker(T& lockable) : m_lockable(&lockable) { lock(); }
explicit Locker(T* lockable) : m_lockable(lockable) { lock(); }
Locker(NoLockingNecessaryTag) : m_lockable(nullptr) { }
Locker(std::underlying_type_t<NoLockingNecessaryTag>) = delete;
~Locker()
{
unlock();
}
static Locker tryLock(T& lockable)
{
Locker result(NoLockingNecessary);
if (lockable.tryLock()) {
result.m_lockable = &lockable;
return result;
}
return result;
}
explicit operator bool() const { return !!m_lockable; }
void unlockEarly()
{
unlock();
m_lockable = nullptr;
}
Locker(Locker&& other)
: m_lockable(other.m_lockable)
{
ASSERT(&other != this);
other.m_lockable = nullptr;
}
Locker& operator=(Locker&& other)
{
ASSERT(&other != this);
m_lockable = other.m_lockable;
other.m_lockable = nullptr;
return *this;
}
private:
template<typename>
friend class DropLockForScope;
void unlock()
{
compilerFence();
if (m_lockable) {
TSAN_ANNOTATE_HAPPENS_BEFORE(m_lockable);
m_lockable->unlock();
}
}
void lock()
{
if (m_lockable) {
m_lockable->lock();
TSAN_ANNOTATE_HAPPENS_AFTER(m_lockable);
}
compilerFence();
}
T* m_lockable;
};
template<typename LockType>
Locker<LockType> holdLock(LockType&) WARN_UNUSED_RETURN;
template<typename LockType>
Locker<LockType> holdLock(LockType& lock)
{
return Locker<LockType>(lock);
}
template<typename LockType>
Locker<LockType> holdLockIf(LockType&, bool predicate) WARN_UNUSED_RETURN;
template<typename LockType>
Locker<LockType> holdLockIf(LockType& lock, bool predicate)
{
return Locker<LockType>(predicate ? &lock : nullptr);
}
template<typename LockType>
Locker<LockType> tryHoldLock(LockType&) WARN_UNUSED_RETURN;
template<typename LockType>
Locker<LockType> tryHoldLock(LockType& lock)
{
return Locker<LockType>::tryLock(lock);
}
template<typename LockType>
class DropLockForScope : private AbstractLocker {
WTF_FORBID_HEAP_ALLOCATION(DropLockForScope);
public:
DropLockForScope(Locker<LockType>& lock)
: m_lock(lock)
{
m_lock.unlock();
}
~DropLockForScope()
{
m_lock.lock();
}
private:
Locker<LockType>& m_lock;
};
}
using WTF::AbstractLocker;
using WTF::Locker;
using WTF::NoLockingNecessaryTag;
using WTF::NoLockingNecessary;
using WTF::holdLock;
using WTF::holdLockIf;
using WTF::DropLockForScope;