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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
#ifndef threading_Mutex_h
#define threading_Mutex_h
#include "mozilla/Assertions.h"
#include "mozilla/Attributes.h"
#include "mozilla/Move.h"
#include "mozilla/ThreadLocal.h"
#include "mozilla/Vector.h"
#include <new>
#include <string.h>
namespace js {
class ConditionVariable;
namespace detail {
class MutexImpl
{
public:
struct PlatformData;
MutexImpl();
~MutexImpl();
MutexImpl(MutexImpl&& rhs)
: platformData_(rhs.platformData_)
{
MOZ_ASSERT(this != &rhs, "self move disallowed!");
rhs.platformData_ = nullptr;
}
MutexImpl& operator=(MutexImpl&& rhs) {
this->~MutexImpl();
new (this) MutexImpl(mozilla::Move(rhs));
return *this;
}
bool operator==(const MutexImpl& rhs) {
return platformData_ == rhs.platformData_;
}
protected:
void lock();
void unlock();
private:
MutexImpl(const MutexImpl&) = delete;
void operator=(const MutexImpl&) = delete;
friend class js::ConditionVariable;
PlatformData* platformData() {
MOZ_ASSERT(platformData_);
return platformData_;
};
PlatformData* platformData_;
};
} // namespace detail
// A MutexId secifies the name and mutex order for a mutex.
//
// The mutex order defines the allowed order of mutex acqusition on a single
// thread. Mutexes must be acquired in strictly increasing order. Mutexes with
// the same order may not be held at the same time by that thread.
struct MutexId
{
const char* name;
uint32_t order;
};
#ifndef DEBUG
class Mutex : public detail::MutexImpl
{
public:
static bool Init() { return true; }
static void ShutDown() {}
explicit Mutex(const MutexId& id) {}
using MutexImpl::lock;
using MutexImpl::unlock;
};
#else
// In debug builds, js::Mutex is a wrapper over MutexImpl that checks correct
// locking order is observed.
//
// The class maintains a per-thread stack of currently-held mutexes to enable it
// to check this.
class Mutex : public detail::MutexImpl
{
public:
static bool Init();
static void ShutDown();
explicit Mutex(const MutexId& id)
: id_(id)
{
MOZ_ASSERT(id_.order != 0);
}
void lock();
void unlock();
private:
const MutexId id_;
using MutexVector = mozilla::Vector<const Mutex*>;
static MOZ_THREAD_LOCAL(MutexVector*) HeldMutexStack;
static MutexVector& heldMutexStack();
};
#endif
} // namespace js
#endif // threading_Mutex_h
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