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/*
* Copyright (C) 2013 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#ifndef ART_RUNTIME_GC_REFERENCE_QUEUE_H_
#define ART_RUNTIME_GC_REFERENCE_QUEUE_H_
#include <iosfwd>
#include <string>
#include <vector>
#include "atomic.h"
#include "base/timing_logger.h"
#include "globals.h"
#include "gtest/gtest.h"
#include "jni.h"
#include "locks.h"
#include "offsets.h"
#include "root_visitor.h"
#include "thread_pool.h"
namespace art {
namespace gc {
class Heap;
// Used to temporarily store java.lang.ref.Reference(s) during GC and prior to queueing on the
// appropriate java.lang.ref.ReferenceQueue. The linked list is maintained in the
// java.lang.ref.Reference objects.
class ReferenceQueue {
public:
explicit ReferenceQueue(Heap* heap);
// Enqueue a reference if is not already enqueued. Thread safe to call from multiple threads
// since it uses a lock to avoid a race between checking for the references presence and adding
// it.
void AtomicEnqueueIfNotEnqueued(Thread* self, mirror::Object* ref)
SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) LOCKS_EXCLUDED(lock_);
// Enqueue a reference, unlike EnqueuePendingReference, enqueue reference checks that the
// reference IsEnqueueable. Not thread safe, used when mutators are paused to minimize lock
// overhead.
void EnqueueReference(mirror::Object* ref) SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
void EnqueuePendingReference(mirror::Object* ref) SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
mirror::Object* DequeuePendingReference() SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
// Enqueues finalizer references with white referents. White referents are blackened, moved to the
// zombie field, and the referent field is cleared.
void EnqueueFinalizerReferences(ReferenceQueue& cleared_references,
RootVisitor is_marked_callback,
RootVisitor recursive_mark_callback, void* arg)
SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
// Walks the reference list marking any references subject to the reference clearing policy.
// References with a black referent are removed from the list. References with white referents
// biased toward saving are blackened and also removed from the list.
void PreserveSomeSoftReferences(RootVisitor preserve_callback, void* arg)
SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
// Unlink the reference list clearing references objects with white referents. Cleared references
// registered to a reference queue are scheduled for appending by the heap worker thread.
void ClearWhiteReferences(ReferenceQueue& cleared_references, RootVisitor visitor, void* arg)
SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
void Dump(std::ostream& os) const
SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
bool IsEmpty() const {
return list_ == nullptr;
}
void Clear() {
list_ = nullptr;
}
mirror::Object* GetList() {
return list_;
}
private:
// Lock, used for parallel GC reference enqueuing. It allows for multiple threads simultaneously
// calling AtomicEnqueueIfNotEnqueued.
Mutex lock_ DEFAULT_MUTEX_ACQUIRED_AFTER;
// The heap contains the reference offsets.
Heap* const heap_;
// The actual reference list. Not a root since it will be nullptr when the GC is not running.
mirror::Object* list_;
};
} // namespace gc
} // namespace art
#endif // ART_RUNTIME_GC_REFERENCE_QUEUE_H_
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