mirror of
https://github.com/mozilla/gecko-dev.git
synced 2024-11-02 07:05:24 +00:00
97 lines
2.5 KiB
C++
97 lines
2.5 KiB
C++
/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
|
|
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
|
|
/* 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_StaticMutex_h
|
|
#define mozilla_StaticMutex_h
|
|
|
|
#include "mozilla/Atomics.h"
|
|
#include "mozilla/Mutex.h"
|
|
|
|
namespace mozilla {
|
|
|
|
/**
|
|
* StaticMutex is a Mutex that can (and in fact, must) be used as a
|
|
* global/static variable.
|
|
*
|
|
* The main reason to use StaticMutex as opposed to
|
|
* StaticAutoPtr<OffTheBooksMutex> is that we instantiate the StaticMutex in a
|
|
* thread-safe manner the first time it's used.
|
|
*
|
|
* The same caveats that apply to StaticAutoPtr apply to StaticMutex. In
|
|
* particular, do not use StaticMutex as a stack variable or a class instance
|
|
* variable, because this class relies on the fact that global variablies are
|
|
* initialized to 0 in order to initialize mMutex. It is only safe to use
|
|
* StaticMutex as a global or static variable.
|
|
*/
|
|
class MOZ_ONLY_USED_TO_AVOID_STATIC_CONSTRUCTORS StaticMutex
|
|
{
|
|
public:
|
|
// In debug builds, check that mMutex is initialized for us as we expect by
|
|
// the compiler. In non-debug builds, don't declare a constructor so that
|
|
// the compiler can see that the constructor is trivial.
|
|
#ifdef DEBUG
|
|
StaticMutex()
|
|
{
|
|
MOZ_ASSERT(!mMutex);
|
|
}
|
|
#endif
|
|
|
|
void Lock()
|
|
{
|
|
Mutex()->Lock();
|
|
}
|
|
|
|
void Unlock()
|
|
{
|
|
Mutex()->Unlock();
|
|
}
|
|
|
|
void AssertCurrentThreadOwns()
|
|
{
|
|
#ifdef DEBUG
|
|
Mutex()->AssertCurrentThreadOwns();
|
|
#endif
|
|
}
|
|
|
|
private:
|
|
OffTheBooksMutex* Mutex()
|
|
{
|
|
if (mMutex) {
|
|
return mMutex;
|
|
}
|
|
|
|
OffTheBooksMutex* mutex = new OffTheBooksMutex("StaticMutex");
|
|
if (!mMutex.compareExchange(nullptr, mutex)) {
|
|
delete mutex;
|
|
}
|
|
|
|
return mMutex;
|
|
}
|
|
|
|
Atomic<OffTheBooksMutex*> mMutex;
|
|
|
|
|
|
// Disallow copy constructor, but only in debug mode. We only define
|
|
// a default constructor in debug mode (see above); if we declared
|
|
// this constructor always, the compiler wouldn't generate a trivial
|
|
// default constructor for us in non-debug mode.
|
|
#ifdef DEBUG
|
|
StaticMutex(StaticMutex& aOther);
|
|
#endif
|
|
|
|
// Disallow these operators.
|
|
StaticMutex& operator=(StaticMutex* aRhs);
|
|
static void* operator new(size_t) CPP_THROW_NEW;
|
|
static void operator delete(void*);
|
|
};
|
|
|
|
typedef BaseAutoLock<StaticMutex> StaticMutexAutoLock;
|
|
typedef BaseAutoUnlock<StaticMutex> StaticMutexAutoUnlock;
|
|
|
|
} // namespace mozilla
|
|
|
|
#endif
|