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// Copyright 2016 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_TASK_SCHEDULER_SCHEDULER_LOCK_H
#define BASE_TASK_SCHEDULER_SCHEDULER_LOCK_H
#include <memory>
#include "base/base_export.h"
#include "base/macros.h"
#include "base/synchronization/condition_variable.h"
#include "base/synchronization/lock.h"
#include "base/task_scheduler/scheduler_lock_impl.h"
namespace base {
namespace internal {
// SchedulerLock should be used anywhere a lock would be used in the scheduler.
// When DCHECK_IS_ON(), lock checking occurs. Otherwise, SchedulerLock is
// equivalent to base::Lock.
//
// The shape of SchedulerLock is as follows:
// SchedulerLock()
// Default constructor, no predecessor lock.
// DCHECKs
// On Acquisition if any scheduler lock is acquired on this thread.
//
// SchedulerLock(const SchedulerLock* predecessor)
// Constructor that specifies an allowed predecessor for that lock.
// DCHECKs
// On Construction if |predecessor| forms a predecessor lock cycle.
// On Acquisition if the previous lock acquired on the thread is not
// |predecessor|. Okay if there was no previous lock acquired.
//
// void Acquire()
// Acquires the lock.
//
// void Release()
// Releases the lock.
//
// void AssertAcquired().
// DCHECKs if the lock is not acquired.
//
// std::unique_ptr<ConditionVariable> CreateConditionVariable()
// Creates a condition variable using this as a lock.
#if DCHECK_IS_ON()
class SchedulerLock : public SchedulerLockImpl {
public:
SchedulerLock() = default;
explicit SchedulerLock(const SchedulerLock* predecessor)
: SchedulerLockImpl(predecessor) {}
};
#else // DCHECK_IS_ON()
class SchedulerLock : public Lock {
public:
SchedulerLock() = default;
explicit SchedulerLock(const SchedulerLock*) {}
std::unique_ptr<ConditionVariable> CreateConditionVariable() {
return std::unique_ptr<ConditionVariable>(new ConditionVariable(this));
}
};
#endif // DCHECK_IS_ON()
// Provides the same functionality as base::AutoLock for SchedulerLock.
class AutoSchedulerLock {
public:
explicit AutoSchedulerLock(SchedulerLock& lock) : lock_(lock) {
lock_.Acquire();
}
~AutoSchedulerLock() {
lock_.AssertAcquired();
lock_.Release();
}
private:
SchedulerLock& lock_;
DISALLOW_COPY_AND_ASSIGN(AutoSchedulerLock);
};
} // namespace internal
} // namespace base
#endif // BASE_TASK_SCHEDULER_SCHEDULER_LOCK_H
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