cefpython/src/include/base/cef_lock.h at cefpython56 · lineCode/cefpython

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// Redistribution and use in source and binary forms, with or without

// modification, are permitted provided that the following conditions are

// met:

// * Redistributions of source code must retain the above copyright

// notice, this list of conditions and the following disclaimer.

// * Redistributions in binary form must reproduce the above

// copyright notice, this list of conditions and the following disclaimer

// in the documentation and/or other materials provided with the

// distribution.

// * Neither the name of Google Inc. nor the name Chromium Embedded

// Framework nor the names of its contributors may be used to endorse

// or promote products derived from this software without specific prior

// written permission.

// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS

// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT

// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR

// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT

// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,

// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT

// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,

// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY

// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT

// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE

// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

#ifndef CEF_INCLUDE_BASE_CEF_LOCK_H_

#define CEF_INCLUDE_BASE_CEF_LOCK_H_

#pragma once

#if defined(BASE_SYNCHRONIZATION_LOCK_H_)

// Do nothing if the Chromium header has already been included.

// This can happen in cases where Chromium code is used directly by the

// client application. When using Chromium code directly always include

// the Chromium header first to avoid type conflicts.

#elif defined(USING_CHROMIUM_INCLUDES)

// When building CEF include the Chromium header directly.

#include "base/synchronization/lock.h"

#else // !USING_CHROMIUM_INCLUDES

// The following is substantially similar to the Chromium implementation.

// If the Chromium implementation diverges the below implementation should be

// updated to match.

#include "include/base/cef_logging.h"

#include "include/base/cef_macros.h"

#include "include/base/cef_platform_thread.h"

#include "include/base/internal/cef_lock_impl.h"

namespace base {

namespace cef_internal {

// A convenient wrapper for an OS specific critical section. The only real

// intelligence in this class is in debug mode for the support for the

// AssertAcquired() method.

class Lock {

public:

#if !DCHECK_IS_ON() // Optimized wrapper implementation

Lock() : lock_() {}

~Lock() {}

void Acquire() { lock_.Lock(); }

void Release() { lock_.Unlock(); }

// If the lock is not held, take it and return true. If the lock is already

// held by another thread, immediately return false. This must not be called

// by a thread already holding the lock (what happens is undefined and an

// assertion may fail).

bool Try() { return lock_.Try(); }

// Null implementation if not debug.

void AssertAcquired() const {}

#else

Lock();

~Lock();

// NOTE: Although windows critical sections support recursive locks, we do not

// allow this, and we will commonly fire a DCHECK() if a thread attempts to

// acquire the lock a second time (while already holding it).

void Acquire() {

lock_.Lock();

CheckUnheldAndMark();

}

void Release() {

CheckHeldAndUnmark();

lock_.Unlock();

}

bool Try() {

bool rv = lock_.Try();

if (rv) {

CheckUnheldAndMark();

}

return rv;

}

void AssertAcquired() const;

#endif // !DCHECK_IS_ON()

private:

#if DCHECK_IS_ON()

// Members and routines taking care of locks assertions.

// Note that this checks for recursive locks and allows them

// if the variable is set. This is allowed by the underlying implementation

// on windows but not on Posix, so we're doing unneeded checks on Posix.

// It's worth it to share the code.

void CheckHeldAndUnmark();

void CheckUnheldAndMark();

// All private data is implicitly protected by lock_.

// Be VERY careful to only access members under that lock.

base::PlatformThreadRef owning_thread_ref_;

#endif // DCHECK_IS_ON()

// Platform specific underlying lock implementation.

LockImpl lock_;

DISALLOW_COPY_AND_ASSIGN(Lock);

};

// A helper class that acquires the given Lock while the AutoLock is in scope.

class AutoLock {

public:

struct AlreadyAcquired {};

explicit AutoLock(Lock& lock) : lock_(lock) {

lock_.Acquire();

}

AutoLock(Lock& lock, const AlreadyAcquired&) : lock_(lock) {

lock_.AssertAcquired();

}

~AutoLock() {

lock_.AssertAcquired();

lock_.Release();

}

private:

Lock& lock_;

DISALLOW_COPY_AND_ASSIGN(AutoLock);

};

// AutoUnlock is a helper that will Release() the |lock| argument in the

// constructor, and re-Acquire() it in the destructor.

class AutoUnlock {

public:

explicit AutoUnlock(Lock& lock) : lock_(lock) {

// We require our caller to have the lock.

lock_.AssertAcquired();

lock_.Release();

}

~AutoUnlock() {

lock_.Acquire();

}

private:

Lock& lock_;

DISALLOW_COPY_AND_ASSIGN(AutoUnlock);

};

} // namespace cef_internal

// Implement classes in the cef_internal namespace and then expose them to the

// base namespace. This avoids conflicts with the base.lib implementation when

// linking sandbox support on Windows.

using cef_internal::Lock;

using cef_internal::AutoLock;

using cef_internal::AutoUnlock;

} // namespace base

#endif // !USING_CHROMIUM_INCLUDES

#endif // CEF_INCLUDE_BASE_CEF_LOCK_H_

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