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// Copyright (c) 2011 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef BASE_SYNCHRONIZATION_LOCK_IMPL_H_
#define BASE_SYNCHRONIZATION_LOCK_IMPL_H_
#pragma once
#include "build/build_config.h"
#if defined(OS_WIN)
#include <windows.h>
#elif defined(OS_POSIX)
#include <pthread.h>
#endif
#include "base/base_export.h"
#include "base/basictypes.h"
#if defined(OS_MACOSX) && !defined(NDEBUG)
// For Mac debug builds, do some extra checks to make sure a LockImpl is not
// used after it has been freed. This instrumentation is to help track down
// spurious locking errors (EINVAL) which are happening on the bots.
// In particular, I want to make sure they aren't a consequence of having
// used a freed lock object (which can happen for instance when trying to
// post tasks to a destroyed MessageLoop).
// See http://crbug.com/102161 for more details. This instrumentation can be
// removed once that bug has been identified.
#define LOCK_IMPL_CHECK_LIVENESS
#endif
namespace base {
namespace internal {
// This class implements the underlying platform-specific spin-lock mechanism
// used for the Lock class. Most users should not use LockImpl directly, but
// should instead use Lock.
class BASE_EXPORT LockImpl {
public:
#if defined(OS_WIN)
typedef CRITICAL_SECTION OSLockType;
#elif defined(OS_POSIX)
typedef pthread_mutex_t OSLockType;
#endif
LockImpl();
~LockImpl();
// If the lock is not held, take it and return true. If the lock is already
// held by something else, immediately return false.
bool Try();
// Take the lock, blocking until it is available if necessary.
void Lock();
// Release the lock. This must only be called by the lock's holder: after
// a successful call to Try, or a call to Lock.
void Unlock();
// Return the native underlying lock. Not supported for Windows builds.
// TODO(awalker): refactor lock and condition variables so that this is
// unnecessary.
#if !defined(OS_WIN)
OSLockType* os_lock() { return &os_lock_; }
#endif
private:
#ifdef LOCK_IMPL_CHECK_LIVENESS
enum LivenessToken {
LT_ALIVE = 0xCa11ab1e, // 3390155550
LT_DELETED = 0xDecea5ed, // 3738084845
};
void CheckIsAlive();
LivenessToken liveness_token_;
#endif // LOCK_IMPL_CHECK_LIVENESS
OSLockType os_lock_;
DISALLOW_COPY_AND_ASSIGN(LockImpl);
};
} // namespace internal
} // namespace base
#endif // BASE_SYNCHRONIZATION_LOCK_IMPL_H_
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