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/*
* 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/macros.h"
#include "base/mutex.h" // For Locks::mutator_lock_.
#include "mirror/object_reference.h"
namespace art {
class ArtField;
class ArtMethod;
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;
}
class RootVisitor {
public:
virtual ~RootVisitor() { }
// Single root version, not overridable.
ALWAYS_INLINE void VisitRoot(mirror::Object** root, const RootInfo& info)
SHARED_REQUIRES(Locks::mutator_lock_) {
VisitRoots(&root, 1, info);
}
// Single root version, not overridable.
ALWAYS_INLINE void VisitRootIfNonNull(mirror::Object** root, const RootInfo& info)
SHARED_REQUIRES(Locks::mutator_lock_) {
if (*root != nullptr) {
VisitRoot(root, info);
}
}
virtual void VisitRoots(mirror::Object*** roots, size_t count, const RootInfo& info)
SHARED_REQUIRES(Locks::mutator_lock_) = 0;
virtual void VisitRoots(mirror::CompressedReference<mirror::Object>** roots, size_t count,
const RootInfo& info)
SHARED_REQUIRES(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
SHARED_REQUIRES(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
SHARED_REQUIRES(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
SHARED_REQUIRES(Locks::mutator_lock_);
void VisitRoot(RootVisitor* visitor, const RootInfo& info) const
SHARED_REQUIRES(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
SHARED_REQUIRES(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(MirrorType* ref = nullptr) SHARED_REQUIRES(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)
SHARED_REQUIRES(Locks::mutator_lock_) {
if (!root.IsNull()) {
VisitRoot(root);
}
}
template <class MirrorType>
ALWAYS_INLINE void VisitRootIfNonNull(mirror::CompressedReference<MirrorType>* root)
SHARED_REQUIRES(Locks::mutator_lock_) {
if (!root->IsNull()) {
VisitRoot(root);
}
}
template <class MirrorType>
void VisitRoot(GcRoot<MirrorType>& root) SHARED_REQUIRES(Locks::mutator_lock_) {
VisitRoot(root.AddressWithoutBarrier());
}
template <class MirrorType>
void VisitRoot(mirror::CompressedReference<MirrorType>* root)
SHARED_REQUIRES(Locks::mutator_lock_) {
if (UNLIKELY(buffer_pos_ >= kBufferSize)) {
Flush();
}
roots_[buffer_pos_++] = root;
}
void Flush() SHARED_REQUIRES(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_;
};
} // namespace art
#endif // ART_RUNTIME_GC_ROOT_H_