runtime/gc_root.h - platform/art - Git at Google

 /*
  * Copyright (C) 2014 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_ROOT_H_
 #define ART_RUNTIME_GC_ROOT_H_

 #include "base/locks.h"       // For Locks::mutator_lock_.
 #include "base/macros.h"
 #include "mirror/object_reference.h"
 #include "read_barrier_option.h"

 namespace art {
 class ArtField;
 class ArtMethod;
 template<class MirrorType> class ObjPtr;

 namespace mirror {
 class Object;
 }  // namespace mirror

 template <size_t kBufferSize>
 class BufferedRootVisitor;

 // Dependent on pointer size so that we don't have frames that are too big on 64 bit.
 static const size_t kDefaultBufferedRootCount = 1024 / sizeof(void*);

 enum RootType {
   kRootUnknown = 0,
   kRootJNIGlobal,
   kRootJNILocal,
   kRootJavaFrame,
   kRootNativeStack,
   kRootStickyClass,
   kRootThreadBlock,
   kRootMonitorUsed,
   kRootThreadObject,
   kRootInternedString,
   kRootFinalizing,  // used for HPROF's conversion to HprofHeapTag
   kRootDebugger,
   kRootReferenceCleanup,  // used for HPROF's conversion to HprofHeapTag
   kRootVMInternal,
   kRootJNIMonitor,
 };
 std::ostream& operator<<(std::ostream& os, const RootType& root_type);

 // Only used by hprof. thread_id_ and type_ are only used by hprof.
 class RootInfo {
  public:
   // Thread id 0 is for non thread roots.
   explicit RootInfo(RootType type, uint32_t thread_id = 0)
      : type_(type), thread_id_(thread_id) {
   }
   RootInfo(const RootInfo&) = default;
   virtual ~RootInfo() {
   }
   RootType GetType() const {
     return type_;
   }
   uint32_t GetThreadId() const {
     return thread_id_;
   }
   virtual void Describe(std::ostream& os) const {
     os << "Type=" << type_ << " thread_id=" << thread_id_;
   }
   std::string ToString() const;

  private:
   const RootType type_;
   const uint32_t thread_id_;
 };

 inline std::ostream& operator<<(std::ostream& os, const RootInfo& root_info) {
   root_info.Describe(os);
   return os;
 }

 // Not all combinations of flags are valid. You may not visit all roots as well as the new roots
 // (no logical reason to do this). You also may not start logging new roots and stop logging new
 // roots (also no logical reason to do this).
 //
 // The precise flag ensures that more metadata is supplied. An example is vreg data for compiled
 // method frames.
 enum VisitRootFlags : uint8_t {
   kVisitRootFlagAllRoots = 0x1,
   kVisitRootFlagNewRoots = 0x2,
   kVisitRootFlagStartLoggingNewRoots = 0x4,
   kVisitRootFlagStopLoggingNewRoots = 0x8,
   kVisitRootFlagClearRootLog = 0x10,
   kVisitRootFlagClassLoader = 0x20,
   kVisitRootFlagPrecise = 0x80,
 };

 class RootVisitor {
  public:
   virtual ~RootVisitor() { }

   // Single root version, not overridable.
   ALWAYS_INLINE void VisitRoot(mirror::Object** root, const RootInfo& info)
       REQUIRES_SHARED(Locks::mutator_lock_) {
     VisitRoots(&root, 1, info);
   }

   // Single root version, not overridable.
   ALWAYS_INLINE void VisitRootIfNonNull(mirror::Object** root, const RootInfo& info)
       REQUIRES_SHARED(Locks::mutator_lock_) {
     if (*root != nullptr) {
       VisitRoot(root, info);
     }
   }

   virtual void VisitRoots(mirror::Object*** roots, size_t count, const RootInfo& info)
       REQUIRES_SHARED(Locks::mutator_lock_) = 0;

   virtual void VisitRoots(mirror::CompressedReference<mirror::Object>** roots, size_t count,
                           const RootInfo& info)
       REQUIRES_SHARED(Locks::mutator_lock_) = 0;
 };

 // Only visits roots one at a time, doesn't handle updating roots. Used when performance isn't
 // critical.
 class SingleRootVisitor : public RootVisitor {
  private:
   void VisitRoots(mirror::Object*** roots, size_t count, const RootInfo& info) override
       REQUIRES_SHARED(Locks::mutator_lock_) {
     for (size_t i = 0; i < count; ++i) {
       VisitRoot(*roots[i], info);
     }
   }

   void VisitRoots(mirror::CompressedReference<mirror::Object>** roots, size_t count,
                           const RootInfo& info) override
       REQUIRES_SHARED(Locks::mutator_lock_) {
     for (size_t i = 0; i < count; ++i) {
       VisitRoot(roots[i]->AsMirrorPtr(), info);
     }
   }

   virtual void VisitRoot(mirror::Object* root, const RootInfo& info) = 0;
 };

 class GcRootSource {
  public:
   GcRootSource()
       : field_(nullptr), method_(nullptr) {
   }
   explicit GcRootSource(ArtField* field)
       : field_(field), method_(nullptr) {
   }
   explicit GcRootSource(ArtMethod* method)
       : field_(nullptr), method_(method) {
   }
   ArtField* GetArtField() const {
     return field_;
   }
   ArtMethod* GetArtMethod() const {
     return method_;
   }
   bool HasArtField() const {
     return field_ != nullptr;
   }
   bool HasArtMethod() const {
     return method_ != nullptr;
   }

  private:
   ArtField* const field_;
   ArtMethod* const method_;

   DISALLOW_COPY_AND_ASSIGN(GcRootSource);
 };

 template<class MirrorType>
 class GcRoot {
  public:
   template<ReadBarrierOption kReadBarrierOption = kWithReadBarrier>
   ALWAYS_INLINE MirrorType* Read(GcRootSource* gc_root_source = nullptr) const
       REQUIRES_SHARED(Locks::mutator_lock_);

   void VisitRoot(RootVisitor* visitor, const RootInfo& info) const
       REQUIRES_SHARED(Locks::mutator_lock_) {
     DCHECK(!IsNull());
     mirror::CompressedReference<mirror::Object>* roots[1] = { &root_ };
     visitor->VisitRoots(roots, 1u, info);
     DCHECK(!IsNull());
   }

   void VisitRootIfNonNull(RootVisitor* visitor, const RootInfo& info) const
       REQUIRES_SHARED(Locks::mutator_lock_) {
     if (!IsNull()) {
       VisitRoot(visitor, info);
     }
   }

   ALWAYS_INLINE mirror::CompressedReference<mirror::Object>* AddressWithoutBarrier() {
     return &root_;
   }

   ALWAYS_INLINE bool IsNull() const {
     // It's safe to null-check it without a read barrier.
     return root_.IsNull();
   }

   ALWAYS_INLINE GcRoot() {}
   explicit ALWAYS_INLINE GcRoot(MirrorType* ref)
       REQUIRES_SHARED(Locks::mutator_lock_);
   explicit ALWAYS_INLINE GcRoot(ObjPtr<MirrorType> ref)
       REQUIRES_SHARED(Locks::mutator_lock_);

  private:
   // Root visitors take pointers to root_ and place them in CompressedReference** arrays. We use a
   // CompressedReference<mirror::Object> here since it violates strict aliasing requirements to
   // cast CompressedReference<MirrorType>* to CompressedReference<mirror::Object>*.
   mutable mirror::CompressedReference<mirror::Object> root_;

   template <size_t kBufferSize> friend class BufferedRootVisitor;
 };

 // Simple data structure for buffered root visiting to avoid virtual dispatch overhead. Currently
 // only for CompressedReferences since these are more common than the Object** roots which are only
 // for thread local roots.
 template <size_t kBufferSize>
 class BufferedRootVisitor {
  public:
   BufferedRootVisitor(RootVisitor* visitor, const RootInfo& root_info)
       : visitor_(visitor), root_info_(root_info), buffer_pos_(0) {
   }

   ~BufferedRootVisitor() {
     Flush();
   }

   template <class MirrorType>
   ALWAYS_INLINE void VisitRootIfNonNull(GcRoot<MirrorType>& root)
       REQUIRES_SHARED(Locks::mutator_lock_) {
     if (!root.IsNull()) {
       VisitRoot(root);
     }
   }

   template <class MirrorType>
   ALWAYS_INLINE void VisitRootIfNonNull(mirror::CompressedReference<MirrorType>* root)
       REQUIRES_SHARED(Locks::mutator_lock_) {
     if (!root->IsNull()) {
       VisitRoot(root);
     }
   }

   template <class MirrorType>
   void VisitRoot(GcRoot<MirrorType>& root) REQUIRES_SHARED(Locks::mutator_lock_) {
     VisitRoot(root.AddressWithoutBarrier());
   }

   template <class MirrorType>
   void VisitRoot(mirror::CompressedReference<MirrorType>* root)
       REQUIRES_SHARED(Locks::mutator_lock_) {
     if (UNLIKELY(buffer_pos_ >= kBufferSize)) {
       Flush();
     }
     roots_[buffer_pos_++] = root;
   }

   void Flush() REQUIRES_SHARED(Locks::mutator_lock_) {
     visitor_->VisitRoots(roots_, buffer_pos_, root_info_);
     buffer_pos_ = 0;
   }

  private:
   RootVisitor* const visitor_;
   RootInfo root_info_;
   mirror::CompressedReference<mirror::Object>* roots_[kBufferSize];
   size_t buffer_pos_;
 };

 class UnbufferedRootVisitor {
  public:
   UnbufferedRootVisitor(RootVisitor* visitor, const RootInfo& root_info)
       : visitor_(visitor), root_info_(root_info) {}

   template <class MirrorType>
   ALWAYS_INLINE void VisitRootIfNonNull(GcRoot<MirrorType>& root) const
       REQUIRES_SHARED(Locks::mutator_lock_) {
     if (!root.IsNull()) {
       VisitRoot(root);
     }
   }

   template <class MirrorType>
   ALWAYS_INLINE void VisitRootIfNonNull(mirror::CompressedReference<MirrorType>* root) const
       REQUIRES_SHARED(Locks::mutator_lock_) {
     if (!root->IsNull()) {
       VisitRoot(root);
     }
   }

   template <class MirrorType>
   void VisitRoot(GcRoot<MirrorType>& root) const REQUIRES_SHARED(Locks::mutator_lock_) {
     VisitRoot(root.AddressWithoutBarrier());
   }

   template <class MirrorType>
   void VisitRoot(mirror::CompressedReference<MirrorType>* root) const
       REQUIRES_SHARED(Locks::mutator_lock_) {
     visitor_->VisitRoots(&root, 1, root_info_);
   }

  private:
   RootVisitor* const visitor_;
   RootInfo root_info_;
 };

 }  // namespace art

 #endif  // ART_RUNTIME_GC_ROOT_H_
	/*
	* Copyright (C) 2014 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_ROOT_H_
	#define ART_RUNTIME_GC_ROOT_H_

	#include "base/locks.h" // For Locks::mutator_lock_.
	#include "base/macros.h"
	#include "mirror/object_reference.h"
	#include "read_barrier_option.h"

	namespace art {
	class ArtField;
	class ArtMethod;
	template<class MirrorType> class ObjPtr;

	namespace mirror {
	class Object;
	} // namespace mirror

	template <size_t kBufferSize>
	class BufferedRootVisitor;

	// Dependent on pointer size so that we don't have frames that are too big on 64 bit.
	static const size_t kDefaultBufferedRootCount = 1024 / sizeof(void*);

	enum RootType {
	kRootUnknown = 0,
	kRootJNIGlobal,
	kRootJNILocal,
	kRootJavaFrame,
	kRootNativeStack,
	kRootStickyClass,
	kRootThreadBlock,
	kRootMonitorUsed,
	kRootThreadObject,
	kRootInternedString,
	kRootFinalizing, // used for HPROF's conversion to HprofHeapTag
	kRootDebugger,
	kRootReferenceCleanup, // used for HPROF's conversion to HprofHeapTag
	kRootVMInternal,
	kRootJNIMonitor,
	};
	std::ostream& operator<<(std::ostream& os, const RootType& root_type);

	// Only used by hprof. thread_id_ and type_ are only used by hprof.
	class RootInfo {
	public:
	// Thread id 0 is for non thread roots.
	explicit RootInfo(RootType type, uint32_t thread_id = 0)
	: type_(type), thread_id_(thread_id) {
	}
	RootInfo(const RootInfo&) = default;
	virtual ~RootInfo() {
	}
	RootType GetType() const {
	return type_;
	}
	uint32_t GetThreadId() const {
	return thread_id_;
	}
	virtual void Describe(std::ostream& os) const {
	os << "Type=" << type_ << " thread_id=" << thread_id_;
	}
	std::string ToString() const;

	private:
	const RootType type_;
	const uint32_t thread_id_;
	};

	inline std::ostream& operator<<(std::ostream& os, const RootInfo& root_info) {
	root_info.Describe(os);
	return os;
	}

	// Not all combinations of flags are valid. You may not visit all roots as well as the new roots
	// (no logical reason to do this). You also may not start logging new roots and stop logging new
	// roots (also no logical reason to do this).
	//
	// The precise flag ensures that more metadata is supplied. An example is vreg data for compiled
	// method frames.
	enum VisitRootFlags : uint8_t {
	kVisitRootFlagAllRoots = 0x1,
	kVisitRootFlagNewRoots = 0x2,
	kVisitRootFlagStartLoggingNewRoots = 0x4,
	kVisitRootFlagStopLoggingNewRoots = 0x8,
	kVisitRootFlagClearRootLog = 0x10,
	kVisitRootFlagClassLoader = 0x20,
	kVisitRootFlagPrecise = 0x80,
	};

	class RootVisitor {
	public:
	virtual ~RootVisitor() { }

	// Single root version, not overridable.
	ALWAYS_INLINE void VisitRoot(mirror::Object** root, const RootInfo& info)
	REQUIRES_SHARED(Locks::mutator_lock_) {
	VisitRoots(&root, 1, info);
	}

	// Single root version, not overridable.
	ALWAYS_INLINE void VisitRootIfNonNull(mirror::Object** root, const RootInfo& info)
	REQUIRES_SHARED(Locks::mutator_lock_) {
	if (*root != nullptr) {
	VisitRoot(root, info);
	}
	}

	virtual void VisitRoots(mirror::Object*** roots, size_t count, const RootInfo& info)
	REQUIRES_SHARED(Locks::mutator_lock_) = 0;

	virtual void VisitRoots(mirror::CompressedReference<mirror::Object>** roots, size_t count,
	const RootInfo& info)
	REQUIRES_SHARED(Locks::mutator_lock_) = 0;
	};

	// Only visits roots one at a time, doesn't handle updating roots. Used when performance isn't
	// critical.
	class SingleRootVisitor : public RootVisitor {
	private:
	void VisitRoots(mirror::Object*** roots, size_t count, const RootInfo& info) override
	REQUIRES_SHARED(Locks::mutator_lock_) {
	for (size_t i = 0; i < count; ++i) {
	VisitRoot(*roots[i], info);
	}
	}

	void VisitRoots(mirror::CompressedReference<mirror::Object>** roots, size_t count,
	const RootInfo& info) override
	REQUIRES_SHARED(Locks::mutator_lock_) {
	for (size_t i = 0; i < count; ++i) {
	VisitRoot(roots[i]->AsMirrorPtr(), info);
	}
	}

	virtual void VisitRoot(mirror::Object* root, const RootInfo& info) = 0;
	};

	class GcRootSource {
	public:
	GcRootSource()
	: field_(nullptr), method_(nullptr) {
	}
	explicit GcRootSource(ArtField* field)
	: field_(field), method_(nullptr) {
	}
	explicit GcRootSource(ArtMethod* method)
	: field_(nullptr), method_(method) {
	}
	ArtField* GetArtField() const {
	return field_;
	}
	ArtMethod* GetArtMethod() const {
	return method_;
	}
	bool HasArtField() const {
	return field_ != nullptr;
	}
	bool HasArtMethod() const {
	return method_ != nullptr;
	}

	private:
	ArtField* const field_;
	ArtMethod* const method_;

	DISALLOW_COPY_AND_ASSIGN(GcRootSource);
	};

	template<class MirrorType>
	class GcRoot {
	public:
	template<ReadBarrierOption kReadBarrierOption = kWithReadBarrier>
	ALWAYS_INLINE MirrorType* Read(GcRootSource* gc_root_source = nullptr) const
	REQUIRES_SHARED(Locks::mutator_lock_);

	void VisitRoot(RootVisitor* visitor, const RootInfo& info) const
	REQUIRES_SHARED(Locks::mutator_lock_) {
	DCHECK(!IsNull());
	mirror::CompressedReference<mirror::Object>* roots[1] = { &root_ };
	visitor->VisitRoots(roots, 1u, info);
	DCHECK(!IsNull());
	}

	void VisitRootIfNonNull(RootVisitor* visitor, const RootInfo& info) const
	REQUIRES_SHARED(Locks::mutator_lock_) {
	if (!IsNull()) {
	VisitRoot(visitor, info);
	}
	}

	ALWAYS_INLINE mirror::CompressedReference<mirror::Object>* AddressWithoutBarrier() {
	return &root_;
	}

	ALWAYS_INLINE bool IsNull() const {
	// It's safe to null-check it without a read barrier.
	return root_.IsNull();
	}

	ALWAYS_INLINE GcRoot() {}
	explicit ALWAYS_INLINE GcRoot(MirrorType* ref)
	REQUIRES_SHARED(Locks::mutator_lock_);
	explicit ALWAYS_INLINE GcRoot(ObjPtr<MirrorType> ref)
	REQUIRES_SHARED(Locks::mutator_lock_);

	private:
	// Root visitors take pointers to root_ and place them in CompressedReference** arrays. We use a
	// CompressedReference<mirror::Object> here since it violates strict aliasing requirements to
	// cast CompressedReference<MirrorType>* to CompressedReference<mirror::Object>*.
	mutable mirror::CompressedReference<mirror::Object> root_;

	template <size_t kBufferSize> friend class BufferedRootVisitor;
	};

	// Simple data structure for buffered root visiting to avoid virtual dispatch overhead. Currently
	// only for CompressedReferences since these are more common than the Object** roots which are only
	// for thread local roots.
	template <size_t kBufferSize>
	class BufferedRootVisitor {
	public:
	BufferedRootVisitor(RootVisitor* visitor, const RootInfo& root_info)
	: visitor_(visitor), root_info_(root_info), buffer_pos_(0) {
	}

	~BufferedRootVisitor() {
	Flush();
	}

	template <class MirrorType>
	ALWAYS_INLINE void VisitRootIfNonNull(GcRoot<MirrorType>& root)
	REQUIRES_SHARED(Locks::mutator_lock_) {
	if (!root.IsNull()) {
	VisitRoot(root);
	}
	}

	template <class MirrorType>
	ALWAYS_INLINE void VisitRootIfNonNull(mirror::CompressedReference<MirrorType>* root)
	REQUIRES_SHARED(Locks::mutator_lock_) {
	if (!root->IsNull()) {
	VisitRoot(root);
	}
	}

	template <class MirrorType>
	void VisitRoot(GcRoot<MirrorType>& root) REQUIRES_SHARED(Locks::mutator_lock_) {
	VisitRoot(root.AddressWithoutBarrier());
	}

	template <class MirrorType>
	void VisitRoot(mirror::CompressedReference<MirrorType>* root)
	REQUIRES_SHARED(Locks::mutator_lock_) {
	if (UNLIKELY(buffer_pos_ >= kBufferSize)) {
	Flush();
	}
	roots_[buffer_pos_++] = root;
	}

	void Flush() REQUIRES_SHARED(Locks::mutator_lock_) {
	visitor_->VisitRoots(roots_, buffer_pos_, root_info_);
	buffer_pos_ = 0;
	}

	private:
	RootVisitor* const visitor_;
	RootInfo root_info_;
	mirror::CompressedReference<mirror::Object>* roots_[kBufferSize];
	size_t buffer_pos_;
	};

	class UnbufferedRootVisitor {
	public:
	UnbufferedRootVisitor(RootVisitor* visitor, const RootInfo& root_info)
	: visitor_(visitor), root_info_(root_info) {}

	template <class MirrorType>
	ALWAYS_INLINE void VisitRootIfNonNull(GcRoot<MirrorType>& root) const
	REQUIRES_SHARED(Locks::mutator_lock_) {
	if (!root.IsNull()) {
	VisitRoot(root);
	}
	}

	template <class MirrorType>
	ALWAYS_INLINE void VisitRootIfNonNull(mirror::CompressedReference<MirrorType>* root) const
	REQUIRES_SHARED(Locks::mutator_lock_) {
	if (!root->IsNull()) {
	VisitRoot(root);
	}
	}

	template <class MirrorType>
	void VisitRoot(GcRoot<MirrorType>& root) const REQUIRES_SHARED(Locks::mutator_lock_) {
	VisitRoot(root.AddressWithoutBarrier());
	}

	template <class MirrorType>
	void VisitRoot(mirror::CompressedReference<MirrorType>* root) const
	REQUIRES_SHARED(Locks::mutator_lock_) {
	visitor_->VisitRoots(&root, 1, root_info_);
	}

	private:
	RootVisitor* const visitor_;
	RootInfo root_info_;
	};

	} // namespace art

	#endif // ART_RUNTIME_GC_ROOT_H_