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 "object_callbacks.h"
24 #include "reference_queue.h"
25 
26 namespace art {
27 
28 class TimingLogger;
29 
30 namespace mirror {
31 class FinalizerReference;
32 class Object;
33 class Reference;
34 }  // namespace mirror
35 
36 namespace gc {
37 
38 class Heap;
39 
40 // Used to process java.lang.References concurrently or paused.
41 class ReferenceProcessor {
42  public:
43   explicit ReferenceProcessor();
44   static bool PreserveSoftReferenceCallback(mirror::HeapReference<mirror::Object>* obj, void* arg)
45       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
46   void ProcessReferences(bool concurrent, TimingLogger* timings, bool clear_soft_references,
47                          IsHeapReferenceMarkedCallback* is_marked_callback,
48                          MarkObjectCallback* mark_object_callback,
49                          ProcessMarkStackCallback* process_mark_stack_callback, void* arg)
50       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_)
51       EXCLUSIVE_LOCKS_REQUIRED(Locks::heap_bitmap_lock_)
52       LOCKS_EXCLUDED(Locks::reference_processor_lock_);
53   // The slow path bool is contained in the reference class object, can only be set once
54   // Only allow setting this with mutators suspended so that we can avoid using a lock in the
55   // GetReferent fast path as an optimization.
56   void EnableSlowPath() EXCLUSIVE_LOCKS_REQUIRED(Locks::mutator_lock_);
57   // Decode the referent, may block if references are being processed.
58   mirror::Object* GetReferent(Thread* self, mirror::Reference* reference)
59       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) LOCKS_EXCLUDED(Locks::reference_processor_lock_);
60   void EnqueueClearedReferences(Thread* self) LOCKS_EXCLUDED(Locks::mutator_lock_);
61   void DelayReferenceReferent(mirror::Class* klass, mirror::Reference* ref,
62                               IsHeapReferenceMarkedCallback* is_marked_callback, void* arg)
63       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
64   void UpdateRoots(IsMarkedCallback* callback, void* arg)
65       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_, Locks::heap_bitmap_lock_);
66   // Make a circular list with reference if it is not enqueued. Uses the finalizer queue lock.
67   bool MakeCircularListIfUnenqueued(mirror::FinalizerReference* reference)
68       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_)
69       LOCKS_EXCLUDED(Locks::reference_processor_lock_,
70                      Locks::reference_queue_finalizer_references_lock_);
71 
72  private:
73   class ProcessReferencesArgs {
74    public:
ProcessReferencesArgs(IsHeapReferenceMarkedCallback * is_marked_callback,MarkObjectCallback * mark_callback,void * arg)75     ProcessReferencesArgs(IsHeapReferenceMarkedCallback* is_marked_callback,
76                           MarkObjectCallback* mark_callback, void* arg)
77         : is_marked_callback_(is_marked_callback), mark_callback_(mark_callback), arg_(arg) {
78     }
79 
80     // The is marked callback is null when the args aren't set up.
81     IsHeapReferenceMarkedCallback* is_marked_callback_;
82     MarkObjectCallback* mark_callback_;
83     void* arg_;
84   };
85   bool SlowPathEnabled() SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
86   // Called by ProcessReferences.
87   void DisableSlowPath(Thread* self) EXCLUSIVE_LOCKS_REQUIRED(Locks::reference_processor_lock_)
88       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
89   // If we are preserving references it means that some dead objects may become live, we use start
90   // and stop preserving to block mutators using GetReferrent from getting access to these
91   // referents.
92   void StartPreservingReferences(Thread* self) LOCKS_EXCLUDED(Locks::reference_processor_lock_);
93   void StopPreservingReferences(Thread* self) LOCKS_EXCLUDED(Locks::reference_processor_lock_);
94   // Process args, used by the GetReferent to return referents which are already marked.
95   ProcessReferencesArgs process_references_args_ GUARDED_BY(Locks::reference_processor_lock_);
96   // Boolean for whether or not we are preserving references (either soft references or finalizers).
97   // If this is true, then we cannot return a referent (see comment in GetReferent).
98   bool preserving_references_ GUARDED_BY(Locks::reference_processor_lock_);
99   // Condition that people wait on if they attempt to get the referent of a reference while
100   // processing is in progress.
101   ConditionVariable condition_ GUARDED_BY(Locks::reference_processor_lock_);
102   // Reference queues used by the GC.
103   ReferenceQueue soft_reference_queue_;
104   ReferenceQueue weak_reference_queue_;
105   ReferenceQueue finalizer_reference_queue_;
106   ReferenceQueue phantom_reference_queue_;
107   ReferenceQueue cleared_references_;
108 };
109 
110 }  // namespace gc
111 }  // namespace art
112 
113 #endif  // ART_RUNTIME_GC_REFERENCE_PROCESSOR_H_
114