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      1 /*
      2  * Copyright (C) 2014 The Android Open Source Project
      3  *
      4  * Licensed under the Apache License, Version 2.0 (the "License");
      5  * you may not use this file except in compliance with the License.
      6  * You may obtain a copy of the License at
      7  *
      8  *      http://www.apache.org/licenses/LICENSE-2.0
      9  *
     10  * Unless required by applicable law or agreed to in writing, software
     11  * distributed under the License is distributed on an "AS IS" BASIS,
     12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     13  * See the License for the specific language governing permissions and
     14  * limitations under the License.
     15  */
     16 
     17 #ifndef ART_RUNTIME_GC_REFERENCE_PROCESSOR_H_
     18 #define ART_RUNTIME_GC_REFERENCE_PROCESSOR_H_
     19 
     20 #include "base/mutex.h"
     21 #include "globals.h"
     22 #include "jni.h"
     23 #include "reference_queue.h"
     24 
     25 namespace art {
     26 
     27 class IsMarkedVisitor;
     28 class TimingLogger;
     29 
     30 namespace mirror {
     31 class Class;
     32 class FinalizerReference;
     33 class Object;
     34 class Reference;
     35 }  // namespace mirror
     36 
     37 namespace gc {
     38 
     39 namespace collector {
     40 class GarbageCollector;
     41 }  // namespace collector
     42 
     43 class Heap;
     44 
     45 // Used to process java.lang.ref.Reference instances concurrently or paused.
     46 class ReferenceProcessor {
     47  public:
     48   explicit ReferenceProcessor();
     49   void ProcessReferences(bool concurrent,
     50                          TimingLogger* timings,
     51                          bool clear_soft_references,
     52                          gc::collector::GarbageCollector* collector)
     53       REQUIRES_SHARED(Locks::mutator_lock_)
     54       REQUIRES(Locks::heap_bitmap_lock_)
     55       REQUIRES(!Locks::reference_processor_lock_);
     56   // The slow path bool is contained in the reference class object, can only be set once
     57   // Only allow setting this with mutators suspended so that we can avoid using a lock in the
     58   // GetReferent fast path as an optimization.
     59   void EnableSlowPath() REQUIRES_SHARED(Locks::mutator_lock_);
     60   void BroadcastForSlowPath(Thread* self);
     61   // Decode the referent, may block if references are being processed.
     62   ObjPtr<mirror::Object> GetReferent(Thread* self, ObjPtr<mirror::Reference> reference)
     63       REQUIRES_SHARED(Locks::mutator_lock_) REQUIRES(!Locks::reference_processor_lock_);
     64   void EnqueueClearedReferences(Thread* self) REQUIRES(!Locks::mutator_lock_);
     65   void DelayReferenceReferent(ObjPtr<mirror::Class> klass,
     66                               ObjPtr<mirror::Reference> ref,
     67                               collector::GarbageCollector* collector)
     68       REQUIRES_SHARED(Locks::mutator_lock_);
     69   void UpdateRoots(IsMarkedVisitor* visitor)
     70       REQUIRES_SHARED(Locks::mutator_lock_, Locks::heap_bitmap_lock_);
     71   // Make a circular list with reference if it is not enqueued. Uses the finalizer queue lock.
     72   bool MakeCircularListIfUnenqueued(ObjPtr<mirror::FinalizerReference> reference)
     73       REQUIRES_SHARED(Locks::mutator_lock_)
     74       REQUIRES(!Locks::reference_processor_lock_,
     75                !Locks::reference_queue_finalizer_references_lock_);
     76   void ClearReferent(ObjPtr<mirror::Reference> ref)
     77       REQUIRES_SHARED(Locks::mutator_lock_)
     78       REQUIRES(!Locks::reference_processor_lock_);
     79 
     80  private:
     81   bool SlowPathEnabled() REQUIRES_SHARED(Locks::mutator_lock_);
     82   // Called by ProcessReferences.
     83   void DisableSlowPath(Thread* self) REQUIRES(Locks::reference_processor_lock_)
     84       REQUIRES_SHARED(Locks::mutator_lock_);
     85   // If we are preserving references it means that some dead objects may become live, we use start
     86   // and stop preserving to block mutators using GetReferrent from getting access to these
     87   // referents.
     88   void StartPreservingReferences(Thread* self) REQUIRES(!Locks::reference_processor_lock_);
     89   void StopPreservingReferences(Thread* self) REQUIRES(!Locks::reference_processor_lock_);
     90   // Wait until reference processing is done.
     91   void WaitUntilDoneProcessingReferences(Thread* self)
     92       REQUIRES_SHARED(Locks::mutator_lock_)
     93       REQUIRES(Locks::reference_processor_lock_);
     94   // Collector which is clearing references, used by the GetReferent to return referents which are
     95   // already marked.
     96   collector::GarbageCollector* collector_ GUARDED_BY(Locks::reference_processor_lock_);
     97   // Boolean for whether or not we are preserving references (either soft references or finalizers).
     98   // If this is true, then we cannot return a referent (see comment in GetReferent).
     99   bool preserving_references_ GUARDED_BY(Locks::reference_processor_lock_);
    100   // Condition that people wait on if they attempt to get the referent of a reference while
    101   // processing is in progress.
    102   ConditionVariable condition_ GUARDED_BY(Locks::reference_processor_lock_);
    103   // Reference queues used by the GC.
    104   ReferenceQueue soft_reference_queue_;
    105   ReferenceQueue weak_reference_queue_;
    106   ReferenceQueue finalizer_reference_queue_;
    107   ReferenceQueue phantom_reference_queue_;
    108   ReferenceQueue cleared_references_;
    109 
    110   DISALLOW_COPY_AND_ASSIGN(ReferenceProcessor);
    111 };
    112 
    113 }  // namespace gc
    114 }  // namespace art
    115 
    116 #endif  // ART_RUNTIME_GC_REFERENCE_PROCESSOR_H_
    117