cef/include/base/cef_lock.h

175 lines
5.5 KiB
C++

// Copyright (c) 2014 Marshall A. Greenblatt. Portions copyright (c) 2011
// Google Inc. All rights reserved.
//
// 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(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_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(const Lock&) = delete;
Lock& operator=(const Lock&) = delete;
~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_;
};
// 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(const AutoLock&) = delete;
AutoLock& operator=(const AutoLock&) = delete;
~AutoLock() {
lock_.AssertAcquired();
lock_.Release();
}
private:
Lock& lock_;
};
// 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(const AutoUnlock&) = delete;
AutoUnlock& operator=(const AutoUnlock&) = delete;
~AutoUnlock() { lock_.Acquire(); }
private:
Lock& lock_;
};
} // 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::AutoLock;
using cef_internal::AutoUnlock;
using cef_internal::Lock;
} // namespace base
#endif // !USING_CHROMIUM_INCLUDES
#endif // CEF_INCLUDE_BASE_CEF_LOCK_H_