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130 lines
4.7 KiB
130 lines
4.7 KiB
/*
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* Copyright (C) 2013 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#ifndef ART_RUNTIME_GC_REFERENCE_QUEUE_H_
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#define ART_RUNTIME_GC_REFERENCE_QUEUE_H_
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#include <iosfwd>
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#include <string>
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#include <vector>
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#include "base/atomic.h"
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#include "base/locks.h"
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#include "base/timing_logger.h"
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#include "jni.h"
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#include "obj_ptr.h"
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#include "offsets.h"
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#include "runtime_globals.h"
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#include "thread_pool.h"
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namespace art {
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class Mutex;
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namespace mirror {
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class Reference;
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} // namespace mirror
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class IsMarkedVisitor;
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class MarkObjectVisitor;
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namespace gc {
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namespace collector {
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class GarbageCollector;
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} // namespace collector
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class Heap;
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// Used to temporarily store java.lang.ref.Reference(s) during GC and prior to queueing on the
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// appropriate java.lang.ref.ReferenceQueue. The linked list is maintained as an unordered,
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// circular, and singly-linked list using the pendingNext fields of the java.lang.ref.Reference
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// objects.
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class ReferenceQueue {
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public:
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explicit ReferenceQueue(Mutex* lock);
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// Enqueue a reference if it is unprocessed. Thread safe to call from multiple
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// threads since it uses a lock to avoid a race between checking for the references presence and
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// adding it.
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void AtomicEnqueueIfNotEnqueued(Thread* self, ObjPtr<mirror::Reference> ref)
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REQUIRES_SHARED(Locks::mutator_lock_) REQUIRES(!*lock_);
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// Enqueue a reference. The reference must be unprocessed.
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// Not thread safe, used when mutators are paused to minimize lock overhead.
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void EnqueueReference(ObjPtr<mirror::Reference> ref) REQUIRES_SHARED(Locks::mutator_lock_);
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// Dequeue a reference from the queue and return that dequeued reference.
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// Call DisableReadBarrierForReference for the reference that's returned from this function.
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ObjPtr<mirror::Reference> DequeuePendingReference() REQUIRES_SHARED(Locks::mutator_lock_);
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// If applicable, disable the read barrier for the reference after its referent is handled (see
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// ConcurrentCopying::ProcessMarkStackRef.) This must be called for a reference that's dequeued
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// from pending queue (DequeuePendingReference).
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void DisableReadBarrierForReference(ObjPtr<mirror::Reference> ref)
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REQUIRES_SHARED(Locks::mutator_lock_);
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// Enqueues finalizer references with white referents. White referents are blackened, moved to
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// the zombie field, and the referent field is cleared.
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void EnqueueFinalizerReferences(ReferenceQueue* cleared_references,
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collector::GarbageCollector* collector)
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REQUIRES_SHARED(Locks::mutator_lock_);
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// Walks the reference list marking any references subject to the reference clearing policy.
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// References with a black referent are removed from the list. References with white referents
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// biased toward saving are blackened and also removed from the list.
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void ForwardSoftReferences(MarkObjectVisitor* visitor)
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REQUIRES_SHARED(Locks::mutator_lock_);
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// Unlink the reference list clearing references objects with white referents. Cleared references
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// registered to a reference queue are scheduled for appending by the heap worker thread.
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void ClearWhiteReferences(ReferenceQueue* cleared_references,
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collector::GarbageCollector* collector)
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REQUIRES_SHARED(Locks::mutator_lock_);
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void Dump(std::ostream& os) const REQUIRES_SHARED(Locks::mutator_lock_);
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size_t GetLength() const REQUIRES_SHARED(Locks::mutator_lock_);
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bool IsEmpty() const {
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return list_ == nullptr;
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}
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void Clear() {
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list_ = nullptr;
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}
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mirror::Reference* GetList() REQUIRES_SHARED(Locks::mutator_lock_) {
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return list_;
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}
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// Visits list_, currently only used for the mark compact GC.
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void UpdateRoots(IsMarkedVisitor* visitor)
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REQUIRES_SHARED(Locks::mutator_lock_);
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private:
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// Lock, used for parallel GC reference enqueuing. It allows for multiple threads simultaneously
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// calling AtomicEnqueueIfNotEnqueued.
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Mutex* const lock_;
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// The actual reference list. Only a root for the mark compact GC since it will be null for other
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// GC types. Not an ObjPtr since it is accessed from multiple threads.
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mirror::Reference* list_;
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DISALLOW_IMPLICIT_CONSTRUCTORS(ReferenceQueue);
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};
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} // namespace gc
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} // namespace art
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#endif // ART_RUNTIME_GC_REFERENCE_QUEUE_H_
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