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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 mozilla_CrossProcessMutex_h
#define mozilla_CrossProcessMutex_h
#include "base/process.h"
#include "mozilla/Mutex.h"
#if defined(OS_LINUX)
#include <pthread.h>
#include "SharedMemoryBasic.h"
#include "mozilla/Atomics.h"
#endif
namespace IPC {
template<typename T>
struct ParamTraits;
}
//
// Provides:
//
// - CrossProcessMutex, a non-recursive mutex that can be shared across processes
// - CrossProcessMutexAutoLock, an RAII class for ensuring that Mutexes are
// properly locked and unlocked
//
// Using CrossProcessMutexAutoLock/CrossProcessMutexAutoUnlock is MUCH
// preferred to making bare calls to CrossProcessMutex.Lock and Unlock.
//
namespace mozilla {
#ifdef XP_WIN
typedef HANDLE CrossProcessMutexHandle;
#elif defined(OS_LINUX)
typedef mozilla::ipc::SharedMemoryBasic::Handle CrossProcessMutexHandle;
#else
// Stub for other platforms. We can't use uintptr_t here since different
// processes could disagree on its size.
typedef uintptr_t CrossProcessMutexHandle;
#endif
class NS_COM_GLUE CrossProcessMutex
{
public:
/**
* CrossProcessMutex
* @param name A name which can reference this lock (currently unused)
**/
CrossProcessMutex(const char* aName);
/**
* CrossProcessMutex
* @param handle A handle of an existing cross process mutex that can be
* opened.
*/
CrossProcessMutex(CrossProcessMutexHandle aHandle);
/**
* ~CrossProcessMutex
**/
~CrossProcessMutex();
/**
* Lock
* This will lock the mutex. Any other thread in any other process that
* has access to this mutex calling lock will block execution until the
* initial caller of lock has made a call to Unlock.
*
* If the owning process is terminated unexpectedly the mutex will be
* released.
**/
void Lock();
/**
* Unlock
* This will unlock the mutex. A single thread currently waiting on a lock
* call will resume execution and aquire ownership of the lock. No
* guarantees are made as to the order in which waiting threads will resume
* execution.
**/
void Unlock();
/**
* ShareToProcess
* This function is called to generate a serializable structure that can
* be sent to the specified process and opened on the other side.
*
* @returns A handle that can be shared to another process
*/
CrossProcessMutexHandle ShareToProcess(base::ProcessHandle aTarget);
private:
friend struct IPC::ParamTraits<CrossProcessMutex>;
CrossProcessMutex();
CrossProcessMutex(const CrossProcessMutex&);
CrossProcessMutex &operator=(const CrossProcessMutex&);
#ifdef XP_WIN
HANDLE mMutex;
#elif defined(OS_LINUX)
mozilla::ipc::SharedMemoryBasic* mSharedBuffer;
pthread_mutex_t* mMutex;
mozilla::Atomic<int32_t>* mCount;
#endif
};
typedef BaseAutoLock<CrossProcessMutex> CrossProcessMutexAutoLock;
typedef BaseAutoUnlock<CrossProcessMutex> CrossProcessMutexAutoUnlock;
}
#endif
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