runtime/transaction.cc - SHIFTPHONES/android_art - Gitiles

 /*
  * 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.
  */

 #include "transaction.h"

 #include "base/stl_util.h"
 #include "base/logging.h"
 #include "gc/accounting/card_table-inl.h"
 #include "intern_table.h"
 #include "mirror/object-inl.h"
 #include "mirror/object_array-inl.h"

 #include <list>

 namespace art {

 // TODO: remove (only used for debugging purpose).
 static constexpr bool kEnableTransactionStats = false;

 Transaction::Transaction()
   : log_lock_("transaction log lock", kTransactionLogLock), aborted_(false) {
   CHECK(Runtime::Current()->IsCompiler());
 }

 Transaction::~Transaction() {
   if (kEnableTransactionStats) {
     MutexLock mu(Thread::Current(), log_lock_);
     size_t objects_count = object_logs_.size();
     size_t field_values_count = 0;
     for (auto it : object_logs_) {
       field_values_count += it.second.Size();
     }
     size_t array_count = array_logs_.size();
     size_t array_values_count = 0;
     for (auto it : array_logs_) {
       array_values_count += it.second.Size();
     }
     size_t string_count = intern_string_logs_.size();
     LOG(INFO) << "Transaction::~Transaction"
               << ": objects_count=" << objects_count
               << ", field_values_count=" << field_values_count
               << ", array_count=" << array_count
               << ", array_values_count=" << array_values_count
               << ", string_count=" << string_count;
   }
 }

 void Transaction::Abort(const std::string& abort_message) {
   MutexLock mu(Thread::Current(), log_lock_);
   // We may abort more than once if the java.lang.InternalError thrown at the
   // time of the abort has been caught during execution of a class initializer.
   // We just keep the message of the first abort because it will cause the
   // transaction to be rolled back anyway.
   if (!aborted_) {
     aborted_ = true;
     abort_message_ = abort_message;
   }
 }

 void Transaction::ThrowInternalError(Thread* self) {
   DCHECK(IsAborted());
   std::string abort_msg(GetAbortMessage());
   self->ThrowNewException(self->GetCurrentLocationForThrow(), "Ljava/lang/InternalError;",
                           abort_msg.c_str());
 }

 bool Transaction::IsAborted() {
   MutexLock mu(Thread::Current(), log_lock_);
   return aborted_;
 }

 const std::string& Transaction::GetAbortMessage() {
   MutexLock mu(Thread::Current(), log_lock_);
   return abort_message_;
 }

 void Transaction::RecordWriteFieldBoolean(mirror::Object* obj, MemberOffset field_offset,
                                           uint8_t value, bool is_volatile) {
   DCHECK(obj != nullptr);
   MutexLock mu(Thread::Current(), log_lock_);
   ObjectLog& object_log = object_logs_[obj];
   object_log.LogBooleanValue(field_offset, value, is_volatile);
 }

 void Transaction::RecordWriteFieldByte(mirror::Object* obj, MemberOffset field_offset,
                                        int8_t value, bool is_volatile) {
   DCHECK(obj != nullptr);
   MutexLock mu(Thread::Current(), log_lock_);
   ObjectLog& object_log = object_logs_[obj];
   object_log.LogByteValue(field_offset, value, is_volatile);
 }

 void Transaction::RecordWriteFieldChar(mirror::Object* obj, MemberOffset field_offset,
                                        uint16_t value, bool is_volatile) {
   DCHECK(obj != nullptr);
   MutexLock mu(Thread::Current(), log_lock_);
   ObjectLog& object_log = object_logs_[obj];
   object_log.LogCharValue(field_offset, value, is_volatile);
 }


 void Transaction::RecordWriteFieldShort(mirror::Object* obj, MemberOffset field_offset,
                                         int16_t value, bool is_volatile) {
   DCHECK(obj != nullptr);
   MutexLock mu(Thread::Current(), log_lock_);
   ObjectLog& object_log = object_logs_[obj];
   object_log.LogShortValue(field_offset, value, is_volatile);
 }


 void Transaction::RecordWriteField32(mirror::Object* obj, MemberOffset field_offset, uint32_t value,
                                      bool is_volatile) {
   DCHECK(obj != nullptr);
   MutexLock mu(Thread::Current(), log_lock_);
   ObjectLog& object_log = object_logs_[obj];
   object_log.Log32BitsValue(field_offset, value, is_volatile);
 }

 void Transaction::RecordWriteField64(mirror::Object* obj, MemberOffset field_offset, uint64_t value,
                                      bool is_volatile) {
   DCHECK(obj != nullptr);
   MutexLock mu(Thread::Current(), log_lock_);
   ObjectLog& object_log = object_logs_[obj];
   object_log.Log64BitsValue(field_offset, value, is_volatile);
 }

 void Transaction::RecordWriteFieldReference(mirror::Object* obj, MemberOffset field_offset,
                                             mirror::Object* value, bool is_volatile) {
   DCHECK(obj != nullptr);
   MutexLock mu(Thread::Current(), log_lock_);
   ObjectLog& object_log = object_logs_[obj];
   object_log.LogReferenceValue(field_offset, value, is_volatile);
 }

 void Transaction::RecordWriteArray(mirror::Array* array, size_t index, uint64_t value) {
   DCHECK(array != nullptr);
   DCHECK(array->IsArrayInstance());
   DCHECK(!array->IsObjectArray());
   MutexLock mu(Thread::Current(), log_lock_);
   ArrayLog& array_log = array_logs_[array];
   array_log.LogValue(index, value);
 }

 void Transaction::RecordStrongStringInsertion(mirror::String* s) {
   InternStringLog log(s, InternStringLog::kStrongString, InternStringLog::kInsert);
   LogInternedString(log);
 }

 void Transaction::RecordWeakStringInsertion(mirror::String* s) {
   InternStringLog log(s, InternStringLog::kWeakString, InternStringLog::kInsert);
   LogInternedString(log);
 }

 void Transaction::RecordStrongStringRemoval(mirror::String* s) {
   InternStringLog log(s, InternStringLog::kStrongString, InternStringLog::kRemove);
   LogInternedString(log);
 }

 void Transaction::RecordWeakStringRemoval(mirror::String* s) {
   InternStringLog log(s, InternStringLog::kWeakString, InternStringLog::kRemove);
   LogInternedString(log);
 }

 void Transaction::LogInternedString(const InternStringLog& log) {
   Locks::intern_table_lock_->AssertExclusiveHeld(Thread::Current());
   MutexLock mu(Thread::Current(), log_lock_);
   intern_string_logs_.push_front(log);
 }

 void Transaction::Rollback() {
   CHECK(!Runtime::Current()->IsActiveTransaction());
   Thread* self = Thread::Current();
   self->AssertNoPendingException();
   MutexLock mu1(self, *Locks::intern_table_lock_);
   MutexLock mu2(self, log_lock_);
   UndoObjectModifications();
   UndoArrayModifications();
   UndoInternStringTableModifications();
 }

 void Transaction::UndoObjectModifications() {
   // TODO we may not need to restore objects allocated during this transaction. Or we could directly
   // remove them from the heap.
   for (auto it : object_logs_) {
     it.second.Undo(it.first);
   }
   object_logs_.clear();
 }

 void Transaction::UndoArrayModifications() {
   // TODO we may not need to restore array allocated during this transaction. Or we could directly
   // remove them from the heap.
   for (auto it : array_logs_) {
     it.second.Undo(it.first);
   }
   array_logs_.clear();
 }

 void Transaction::UndoInternStringTableModifications() {
   InternTable* const intern_table = Runtime::Current()->GetInternTable();
   // We want to undo each operation from the most recent to the oldest. List has been filled so the
   // most recent operation is at list begin so just have to iterate over it.
   for (InternStringLog& string_log : intern_string_logs_) {
     string_log.Undo(intern_table);
   }
   intern_string_logs_.clear();
 }

 void Transaction::VisitRoots(RootCallback* callback, void* arg) {
   MutexLock mu(Thread::Current(), log_lock_);
   VisitObjectLogs(callback, arg);
   VisitArrayLogs(callback, arg);
   VisitStringLogs(callback, arg);
 }

 void Transaction::VisitObjectLogs(RootCallback* callback, void* arg) {
   // List of moving roots.
   typedef std::pair<mirror::Object*, mirror::Object*> ObjectPair;
   std::list<ObjectPair> moving_roots;

   // Visit roots.
   for (auto it : object_logs_) {
     it.second.VisitRoots(callback, arg);
     mirror::Object* old_root = it.first;
     mirror::Object* new_root = old_root;
     callback(&new_root, arg, RootInfo(kRootUnknown));
     if (new_root != old_root) {
       moving_roots.push_back(std::make_pair(old_root, new_root));
     }
   }

   // Update object logs with moving roots.
   for (const ObjectPair& pair : moving_roots) {
     mirror::Object* old_root = pair.first;
     mirror::Object* new_root = pair.second;
     auto old_root_it = object_logs_.find(old_root);
     CHECK(old_root_it != object_logs_.end());
     CHECK(object_logs_.find(new_root) == object_logs_.end());
     object_logs_.insert(std::make_pair(new_root, old_root_it->second));
     object_logs_.erase(old_root_it);
   }
 }

 void Transaction::VisitArrayLogs(RootCallback* callback, void* arg) {
   // List of moving roots.
   typedef std::pair<mirror::Array*, mirror::Array*> ArrayPair;
   std::list<ArrayPair> moving_roots;

   for (auto it : array_logs_) {
     mirror::Array* old_root = it.first;
     CHECK(!old_root->IsObjectArray());
     mirror::Array* new_root = old_root;
     callback(reinterpret_cast<mirror::Object**>(&new_root), arg, RootInfo(kRootUnknown));
     if (new_root != old_root) {
       moving_roots.push_back(std::make_pair(old_root, new_root));
     }
   }

   // Update array logs with moving roots.
   for (const ArrayPair& pair : moving_roots) {
     mirror::Array* old_root = pair.first;
     mirror::Array* new_root = pair.second;
     auto old_root_it = array_logs_.find(old_root);
     CHECK(old_root_it != array_logs_.end());
     CHECK(array_logs_.find(new_root) == array_logs_.end());
     array_logs_.insert(std::make_pair(new_root, old_root_it->second));
     array_logs_.erase(old_root_it);
   }
 }

 void Transaction::VisitStringLogs(RootCallback* callback, void* arg) {
   for (InternStringLog& log : intern_string_logs_) {
     log.VisitRoots(callback, arg);
   }
 }

 void Transaction::ObjectLog::LogBooleanValue(MemberOffset offset, uint8_t value, bool is_volatile) {
   LogValue(ObjectLog::kBoolean, offset, value, is_volatile);
 }

 void Transaction::ObjectLog::LogByteValue(MemberOffset offset, int8_t value, bool is_volatile) {
   LogValue(ObjectLog::kByte, offset, value, is_volatile);
 }

 void Transaction::ObjectLog::LogCharValue(MemberOffset offset, uint16_t value, bool is_volatile) {
   LogValue(ObjectLog::kChar, offset, value, is_volatile);
 }

 void Transaction::ObjectLog::LogShortValue(MemberOffset offset, int16_t value, bool is_volatile) {
   LogValue(ObjectLog::kShort, offset, value, is_volatile);
 }

 void Transaction::ObjectLog::Log32BitsValue(MemberOffset offset, uint32_t value, bool is_volatile) {
   LogValue(ObjectLog::k32Bits, offset, value, is_volatile);
 }

 void Transaction::ObjectLog::Log64BitsValue(MemberOffset offset, uint64_t value, bool is_volatile) {
   LogValue(ObjectLog::k64Bits, offset, value, is_volatile);
 }

 void Transaction::ObjectLog::LogReferenceValue(MemberOffset offset, mirror::Object* obj, bool is_volatile) {
   LogValue(ObjectLog::kReference, offset, reinterpret_cast<uintptr_t>(obj), is_volatile);
 }

 void Transaction::ObjectLog::LogValue(ObjectLog::FieldValueKind kind,
                                       MemberOffset offset, uint64_t value, bool is_volatile) {
   auto it = field_values_.find(offset.Uint32Value());
   if (it == field_values_.end()) {
     ObjectLog::FieldValue field_value;
     field_value.value = value;
     field_value.is_volatile = is_volatile;
     field_value.kind = kind;
     field_values_.insert(std::make_pair(offset.Uint32Value(), field_value));
   }
 }

 void Transaction::ObjectLog::Undo(mirror::Object* obj) {
   for (auto& it : field_values_) {
     // Garbage collector needs to access object's class and array's length. So we don't rollback
     // these values.
     MemberOffset field_offset(it.first);
     if (field_offset.Uint32Value() == mirror::Class::ClassOffset().Uint32Value()) {
       // Skip Object::class field.
       continue;
     }
     if (obj->IsArrayInstance() &&
         field_offset.Uint32Value() == mirror::Array::LengthOffset().Uint32Value()) {
       // Skip Array::length field.
       continue;
     }
     FieldValue& field_value = it.second;
     UndoFieldWrite(obj, field_offset, field_value);
   }
 }

 void Transaction::ObjectLog::UndoFieldWrite(mirror::Object* obj, MemberOffset field_offset,
                                             const FieldValue& field_value) {
   // TODO We may want to abort a transaction while still being in transaction mode. In this case,
   // we'd need to disable the check.
   constexpr bool kCheckTransaction = true;
   switch (field_value.kind) {
     case kBoolean:
       if (UNLIKELY(field_value.is_volatile)) {
         obj->SetFieldBooleanVolatile<false, kCheckTransaction>(field_offset,
                                                          static_cast<bool>(field_value.value));
       } else {
         obj->SetFieldBoolean<false, kCheckTransaction>(field_offset,
                                                  static_cast<bool>(field_value.value));
       }
       break;
     case kByte:
       if (UNLIKELY(field_value.is_volatile)) {
         obj->SetFieldByteVolatile<false, kCheckTransaction>(field_offset,
                                                          static_cast<int8_t>(field_value.value));
       } else {
         obj->SetFieldByte<false, kCheckTransaction>(field_offset,
                                                  static_cast<int8_t>(field_value.value));
       }
       break;
     case kChar:
       if (UNLIKELY(field_value.is_volatile)) {
         obj->SetFieldCharVolatile<false, kCheckTransaction>(field_offset,
                                                           static_cast<uint16_t>(field_value.value));
       } else {
         obj->SetFieldChar<false, kCheckTransaction>(field_offset,
                                                   static_cast<uint16_t>(field_value.value));
       }
       break;
     case kShort:
       if (UNLIKELY(field_value.is_volatile)) {
         obj->SetFieldShortVolatile<false, kCheckTransaction>(field_offset,
                                                           static_cast<int16_t>(field_value.value));
       } else {
         obj->SetFieldShort<false, kCheckTransaction>(field_offset,
                                                   static_cast<int16_t>(field_value.value));
       }
       break;
     case k32Bits:
       if (UNLIKELY(field_value.is_volatile)) {
         obj->SetField32Volatile<false, kCheckTransaction>(field_offset,
                                                           static_cast<uint32_t>(field_value.value));
       } else {
         obj->SetField32<false, kCheckTransaction>(field_offset,
                                                   static_cast<uint32_t>(field_value.value));
       }
       break;
     case k64Bits:
       if (UNLIKELY(field_value.is_volatile)) {
         obj->SetField64Volatile<false, kCheckTransaction>(field_offset, field_value.value);
       } else {
         obj->SetField64<false, kCheckTransaction>(field_offset, field_value.value);
       }
       break;
     case kReference:
       if (UNLIKELY(field_value.is_volatile)) {
         obj->SetFieldObjectVolatile<false, kCheckTransaction>(field_offset,
                                                               reinterpret_cast<mirror::Object*>(field_value.value));
       } else {
         obj->SetFieldObject<false, kCheckTransaction>(field_offset,
                                                       reinterpret_cast<mirror::Object*>(field_value.value));
       }
       break;
     default:
       LOG(FATAL) << "Unknown value kind " << static_cast<int>(field_value.kind);
       break;
   }
 }

 void Transaction::ObjectLog::VisitRoots(RootCallback* callback, void* arg) {
   for (auto it : field_values_) {
     FieldValue& field_value = it.second;
     if (field_value.kind == ObjectLog::kReference) {
       mirror::Object* obj =
           reinterpret_cast<mirror::Object*>(static_cast<uintptr_t>(field_value.value));
       if (obj != nullptr) {
         callback(&obj, arg, RootInfo(kRootUnknown));
         field_value.value = reinterpret_cast<uintptr_t>(obj);
       }
     }
   }
 }

 void Transaction::InternStringLog::Undo(InternTable* intern_table) {
   DCHECK(intern_table != nullptr);
   switch (string_op_) {
     case InternStringLog::kInsert: {
       switch (string_kind_) {
         case InternStringLog::kStrongString:
           intern_table->RemoveStrongFromTransaction(str_);
           break;
         case InternStringLog::kWeakString:
           intern_table->RemoveWeakFromTransaction(str_);
           break;
         default:
           LOG(FATAL) << "Unknown interned string kind";
           break;
       }
       break;
     }
     case InternStringLog::kRemove: {
       switch (string_kind_) {
         case InternStringLog::kStrongString:
           intern_table->InsertStrongFromTransaction(str_);
           break;
         case InternStringLog::kWeakString:
           intern_table->InsertWeakFromTransaction(str_);
           break;
         default:
           LOG(FATAL) << "Unknown interned string kind";
           break;
       }
       break;
     }
     default:
       LOG(FATAL) << "Unknown interned string op";
       break;
   }
 }

 void Transaction::InternStringLog::VisitRoots(RootCallback* callback, void* arg) {
   callback(reinterpret_cast<mirror::Object**>(&str_), arg, RootInfo(kRootInternedString));
 }

 void Transaction::ArrayLog::LogValue(size_t index, uint64_t value) {
   auto it = array_values_.find(index);
   if (it == array_values_.end()) {
     array_values_.insert(std::make_pair(index, value));
   }
 }

 void Transaction::ArrayLog::Undo(mirror::Array* array) {
   DCHECK(array != nullptr);
   DCHECK(array->IsArrayInstance());
   Primitive::Type type = array->GetClass()->GetComponentType()->GetPrimitiveType();
   for (auto it : array_values_) {
     UndoArrayWrite(array, type, it.first, it.second);
   }
 }

 void Transaction::ArrayLog::UndoArrayWrite(mirror::Array* array, Primitive::Type array_type,
                                            size_t index, uint64_t value) {
   // TODO We may want to abort a transaction while still being in transaction mode. In this case,
   // we'd need to disable the check.
   switch (array_type) {
     case Primitive::kPrimBoolean:
       array->AsBooleanArray()->SetWithoutChecks<false>(index, static_cast<uint8_t>(value));
       break;
     case Primitive::kPrimByte:
       array->AsByteArray()->SetWithoutChecks<false>(index, static_cast<int8_t>(value));
       break;
     case Primitive::kPrimChar:
       array->AsCharArray()->SetWithoutChecks<false>(index, static_cast<uint16_t>(value));
       break;
     case Primitive::kPrimShort:
       array->AsShortArray()->SetWithoutChecks<false>(index, static_cast<int16_t>(value));
       break;
     case Primitive::kPrimInt:
       array->AsIntArray()->SetWithoutChecks<false>(index, static_cast<int32_t>(value));
       break;
     case Primitive::kPrimFloat:
       array->AsFloatArray()->SetWithoutChecks<false>(index, static_cast<float>(value));
       break;
     case Primitive::kPrimLong:
       array->AsLongArray()->SetWithoutChecks<false>(index, static_cast<int64_t>(value));
       break;
     case Primitive::kPrimDouble:
       array->AsDoubleArray()->SetWithoutChecks<false>(index, static_cast<double>(value));
       break;
     case Primitive::kPrimNot:
       LOG(FATAL) << "ObjectArray should be treated as Object";
       break;
     default:
       LOG(FATAL) << "Unsupported type " << array_type;
   }
 }

 }  // namespace art
	/*
	* 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.
	*/

	#include "transaction.h"

	#include "base/stl_util.h"
	#include "base/logging.h"
	#include "gc/accounting/card_table-inl.h"
	#include "intern_table.h"
	#include "mirror/object-inl.h"
	#include "mirror/object_array-inl.h"

	#include <list>

	namespace art {

	// TODO: remove (only used for debugging purpose).
	static constexpr bool kEnableTransactionStats = false;

	Transaction::Transaction()
	: log_lock_("transaction log lock", kTransactionLogLock), aborted_(false) {
	CHECK(Runtime::Current()->IsCompiler());
	}

	Transaction::~Transaction() {
	if (kEnableTransactionStats) {
	MutexLock mu(Thread::Current(), log_lock_);
	size_t objects_count = object_logs_.size();
	size_t field_values_count = 0;
	for (auto it : object_logs_) {
	field_values_count += it.second.Size();
	}
	size_t array_count = array_logs_.size();
	size_t array_values_count = 0;
	for (auto it : array_logs_) {
	array_values_count += it.second.Size();
	}
	size_t string_count = intern_string_logs_.size();
	LOG(INFO) << "Transaction::~Transaction"
	<< ": objects_count=" << objects_count
	<< ", field_values_count=" << field_values_count
	<< ", array_count=" << array_count
	<< ", array_values_count=" << array_values_count
	<< ", string_count=" << string_count;
	}
	}

	void Transaction::Abort(const std::string& abort_message) {
	MutexLock mu(Thread::Current(), log_lock_);
	// We may abort more than once if the java.lang.InternalError thrown at the
	// time of the abort has been caught during execution of a class initializer.
	// We just keep the message of the first abort because it will cause the
	// transaction to be rolled back anyway.
	if (!aborted_) {
	aborted_ = true;
	abort_message_ = abort_message;
	}
	}

	void Transaction::ThrowInternalError(Thread* self) {
	DCHECK(IsAborted());
	std::string abort_msg(GetAbortMessage());
	self->ThrowNewException(self->GetCurrentLocationForThrow(), "Ljava/lang/InternalError;",
	abort_msg.c_str());
	}

	bool Transaction::IsAborted() {
	MutexLock mu(Thread::Current(), log_lock_);
	return aborted_;
	}

	const std::string& Transaction::GetAbortMessage() {
	MutexLock mu(Thread::Current(), log_lock_);
	return abort_message_;
	}

	void Transaction::RecordWriteFieldBoolean(mirror::Object* obj, MemberOffset field_offset,
	uint8_t value, bool is_volatile) {
	DCHECK(obj != nullptr);
	MutexLock mu(Thread::Current(), log_lock_);
	ObjectLog& object_log = object_logs_[obj];
	object_log.LogBooleanValue(field_offset, value, is_volatile);
	}

	void Transaction::RecordWriteFieldByte(mirror::Object* obj, MemberOffset field_offset,
	int8_t value, bool is_volatile) {
	DCHECK(obj != nullptr);
	MutexLock mu(Thread::Current(), log_lock_);
	ObjectLog& object_log = object_logs_[obj];
	object_log.LogByteValue(field_offset, value, is_volatile);
	}

	void Transaction::RecordWriteFieldChar(mirror::Object* obj, MemberOffset field_offset,
	uint16_t value, bool is_volatile) {
	DCHECK(obj != nullptr);
	MutexLock mu(Thread::Current(), log_lock_);
	ObjectLog& object_log = object_logs_[obj];
	object_log.LogCharValue(field_offset, value, is_volatile);
	}


	void Transaction::RecordWriteFieldShort(mirror::Object* obj, MemberOffset field_offset,
	int16_t value, bool is_volatile) {
	DCHECK(obj != nullptr);
	MutexLock mu(Thread::Current(), log_lock_);
	ObjectLog& object_log = object_logs_[obj];
	object_log.LogShortValue(field_offset, value, is_volatile);
	}


	void Transaction::RecordWriteField32(mirror::Object* obj, MemberOffset field_offset, uint32_t value,
	bool is_volatile) {
	DCHECK(obj != nullptr);
	MutexLock mu(Thread::Current(), log_lock_);
	ObjectLog& object_log = object_logs_[obj];
	object_log.Log32BitsValue(field_offset, value, is_volatile);
	}

	void Transaction::RecordWriteField64(mirror::Object* obj, MemberOffset field_offset, uint64_t value,
	bool is_volatile) {
	DCHECK(obj != nullptr);
	MutexLock mu(Thread::Current(), log_lock_);
	ObjectLog& object_log = object_logs_[obj];
	object_log.Log64BitsValue(field_offset, value, is_volatile);
	}

	void Transaction::RecordWriteFieldReference(mirror::Object* obj, MemberOffset field_offset,
	mirror::Object* value, bool is_volatile) {
	DCHECK(obj != nullptr);
	MutexLock mu(Thread::Current(), log_lock_);
	ObjectLog& object_log = object_logs_[obj];
	object_log.LogReferenceValue(field_offset, value, is_volatile);
	}

	void Transaction::RecordWriteArray(mirror::Array* array, size_t index, uint64_t value) {
	DCHECK(array != nullptr);
	DCHECK(array->IsArrayInstance());
	DCHECK(!array->IsObjectArray());
	MutexLock mu(Thread::Current(), log_lock_);
	ArrayLog& array_log = array_logs_[array];
	array_log.LogValue(index, value);
	}

	void Transaction::RecordStrongStringInsertion(mirror::String* s) {
	InternStringLog log(s, InternStringLog::kStrongString, InternStringLog::kInsert);
	LogInternedString(log);
	}

	void Transaction::RecordWeakStringInsertion(mirror::String* s) {
	InternStringLog log(s, InternStringLog::kWeakString, InternStringLog::kInsert);
	LogInternedString(log);
	}

	void Transaction::RecordStrongStringRemoval(mirror::String* s) {
	InternStringLog log(s, InternStringLog::kStrongString, InternStringLog::kRemove);
	LogInternedString(log);
	}

	void Transaction::RecordWeakStringRemoval(mirror::String* s) {
	InternStringLog log(s, InternStringLog::kWeakString, InternStringLog::kRemove);
	LogInternedString(log);
	}

	void Transaction::LogInternedString(const InternStringLog& log) {
	Locks::intern_table_lock_->AssertExclusiveHeld(Thread::Current());
	MutexLock mu(Thread::Current(), log_lock_);
	intern_string_logs_.push_front(log);
	}

	void Transaction::Rollback() {
	CHECK(!Runtime::Current()->IsActiveTransaction());
	Thread* self = Thread::Current();
	self->AssertNoPendingException();
	MutexLock mu1(self, *Locks::intern_table_lock_);
	MutexLock mu2(self, log_lock_);
	UndoObjectModifications();
	UndoArrayModifications();
	UndoInternStringTableModifications();
	}

	void Transaction::UndoObjectModifications() {
	// TODO we may not need to restore objects allocated during this transaction. Or we could directly
	// remove them from the heap.
	for (auto it : object_logs_) {
	it.second.Undo(it.first);
	}
	object_logs_.clear();
	}

	void Transaction::UndoArrayModifications() {
	// TODO we may not need to restore array allocated during this transaction. Or we could directly
	// remove them from the heap.
	for (auto it : array_logs_) {
	it.second.Undo(it.first);
	}
	array_logs_.clear();
	}

	void Transaction::UndoInternStringTableModifications() {
	InternTable* const intern_table = Runtime::Current()->GetInternTable();
	// We want to undo each operation from the most recent to the oldest. List has been filled so the
	// most recent operation is at list begin so just have to iterate over it.
	for (InternStringLog& string_log : intern_string_logs_) {
	string_log.Undo(intern_table);
	}
	intern_string_logs_.clear();
	}

	void Transaction::VisitRoots(RootCallback* callback, void* arg) {
	MutexLock mu(Thread::Current(), log_lock_);
	VisitObjectLogs(callback, arg);
	VisitArrayLogs(callback, arg);
	VisitStringLogs(callback, arg);
	}

	void Transaction::VisitObjectLogs(RootCallback* callback, void* arg) {
	// List of moving roots.
	typedef std::pair<mirror::Object, mirror::Object> ObjectPair;
	std::list<ObjectPair> moving_roots;

	// Visit roots.
	for (auto it : object_logs_) {
	it.second.VisitRoots(callback, arg);
	mirror::Object* old_root = it.first;
	mirror::Object* new_root = old_root;
	callback(&new_root, arg, RootInfo(kRootUnknown));
	if (new_root != old_root) {
	moving_roots.push_back(std::make_pair(old_root, new_root));
	}
	}

	// Update object logs with moving roots.
	for (const ObjectPair& pair : moving_roots) {
	mirror::Object* old_root = pair.first;
	mirror::Object* new_root = pair.second;
	auto old_root_it = object_logs_.find(old_root);
	CHECK(old_root_it != object_logs_.end());
	CHECK(object_logs_.find(new_root) == object_logs_.end());
	object_logs_.insert(std::make_pair(new_root, old_root_it->second));
	object_logs_.erase(old_root_it);
	}
	}

	void Transaction::VisitArrayLogs(RootCallback* callback, void* arg) {
	// List of moving roots.
	typedef std::pair<mirror::Array, mirror::Array> ArrayPair;
	std::list<ArrayPair> moving_roots;

	for (auto it : array_logs_) {
	mirror::Array* old_root = it.first;
	CHECK(!old_root->IsObjectArray());
	mirror::Array* new_root = old_root;
	callback(reinterpret_cast<mirror::Object**>(&new_root), arg, RootInfo(kRootUnknown));
	if (new_root != old_root) {
	moving_roots.push_back(std::make_pair(old_root, new_root));
	}
	}

	// Update array logs with moving roots.
	for (const ArrayPair& pair : moving_roots) {
	mirror::Array* old_root = pair.first;
	mirror::Array* new_root = pair.second;
	auto old_root_it = array_logs_.find(old_root);
	CHECK(old_root_it != array_logs_.end());
	CHECK(array_logs_.find(new_root) == array_logs_.end());
	array_logs_.insert(std::make_pair(new_root, old_root_it->second));
	array_logs_.erase(old_root_it);
	}
	}

	void Transaction::VisitStringLogs(RootCallback* callback, void* arg) {
	for (InternStringLog& log : intern_string_logs_) {
	log.VisitRoots(callback, arg);
	}
	}

	void Transaction::ObjectLog::LogBooleanValue(MemberOffset offset, uint8_t value, bool is_volatile) {
	LogValue(ObjectLog::kBoolean, offset, value, is_volatile);
	}

	void Transaction::ObjectLog::LogByteValue(MemberOffset offset, int8_t value, bool is_volatile) {
	LogValue(ObjectLog::kByte, offset, value, is_volatile);
	}

	void Transaction::ObjectLog::LogCharValue(MemberOffset offset, uint16_t value, bool is_volatile) {
	LogValue(ObjectLog::kChar, offset, value, is_volatile);
	}

	void Transaction::ObjectLog::LogShortValue(MemberOffset offset, int16_t value, bool is_volatile) {
	LogValue(ObjectLog::kShort, offset, value, is_volatile);
	}

	void Transaction::ObjectLog::Log32BitsValue(MemberOffset offset, uint32_t value, bool is_volatile) {
	LogValue(ObjectLog::k32Bits, offset, value, is_volatile);
	}

	void Transaction::ObjectLog::Log64BitsValue(MemberOffset offset, uint64_t value, bool is_volatile) {
	LogValue(ObjectLog::k64Bits, offset, value, is_volatile);
	}

	void Transaction::ObjectLog::LogReferenceValue(MemberOffset offset, mirror::Object* obj, bool is_volatile) {
	LogValue(ObjectLog::kReference, offset, reinterpret_cast<uintptr_t>(obj), is_volatile);
	}

	void Transaction::ObjectLog::LogValue(ObjectLog::FieldValueKind kind,
	MemberOffset offset, uint64_t value, bool is_volatile) {
	auto it = field_values_.find(offset.Uint32Value());
	if (it == field_values_.end()) {
	ObjectLog::FieldValue field_value;
	field_value.value = value;
	field_value.is_volatile = is_volatile;
	field_value.kind = kind;
	field_values_.insert(std::make_pair(offset.Uint32Value(), field_value));
	}
	}

	void Transaction::ObjectLog::Undo(mirror::Object* obj) {
	for (auto& it : field_values_) {
	// Garbage collector needs to access object's class and array's length. So we don't rollback
	// these values.
	MemberOffset field_offset(it.first);
	if (field_offset.Uint32Value() == mirror::Class::ClassOffset().Uint32Value()) {
	// Skip Object::class field.
	continue;
	}
	if (obj->IsArrayInstance() &&
	field_offset.Uint32Value() == mirror::Array::LengthOffset().Uint32Value()) {
	// Skip Array::length field.
	continue;
	}
	FieldValue& field_value = it.second;
	UndoFieldWrite(obj, field_offset, field_value);
	}
	}

	void Transaction::ObjectLog::UndoFieldWrite(mirror::Object* obj, MemberOffset field_offset,
	const FieldValue& field_value) {
	// TODO We may want to abort a transaction while still being in transaction mode. In this case,
	// we'd need to disable the check.
	constexpr bool kCheckTransaction = true;
	switch (field_value.kind) {
	case kBoolean:
	if (UNLIKELY(field_value.is_volatile)) {
	obj->SetFieldBooleanVolatile<false, kCheckTransaction>(field_offset,
	static_cast<bool>(field_value.value));
	} else {
	obj->SetFieldBoolean<false, kCheckTransaction>(field_offset,
	static_cast<bool>(field_value.value));
	}
	break;
	case kByte:
	if (UNLIKELY(field_value.is_volatile)) {
	obj->SetFieldByteVolatile<false, kCheckTransaction>(field_offset,
	static_cast<int8_t>(field_value.value));
	} else {
	obj->SetFieldByte<false, kCheckTransaction>(field_offset,
	static_cast<int8_t>(field_value.value));
	}
	break;
	case kChar:
	if (UNLIKELY(field_value.is_volatile)) {
	obj->SetFieldCharVolatile<false, kCheckTransaction>(field_offset,
	static_cast<uint16_t>(field_value.value));
	} else {
	obj->SetFieldChar<false, kCheckTransaction>(field_offset,
	static_cast<uint16_t>(field_value.value));
	}
	break;
	case kShort:
	if (UNLIKELY(field_value.is_volatile)) {
	obj->SetFieldShortVolatile<false, kCheckTransaction>(field_offset,
	static_cast<int16_t>(field_value.value));
	} else {
	obj->SetFieldShort<false, kCheckTransaction>(field_offset,
	static_cast<int16_t>(field_value.value));
	}
	break;
	case k32Bits:
	if (UNLIKELY(field_value.is_volatile)) {
	obj->SetField32Volatile<false, kCheckTransaction>(field_offset,
	static_cast<uint32_t>(field_value.value));
	} else {
	obj->SetField32<false, kCheckTransaction>(field_offset,
	static_cast<uint32_t>(field_value.value));
	}
	break;
	case k64Bits:
	if (UNLIKELY(field_value.is_volatile)) {
	obj->SetField64Volatile<false, kCheckTransaction>(field_offset, field_value.value);
	} else {
	obj->SetField64<false, kCheckTransaction>(field_offset, field_value.value);
	}
	break;
	case kReference:
	if (UNLIKELY(field_value.is_volatile)) {
	obj->SetFieldObjectVolatile<false, kCheckTransaction>(field_offset,
	reinterpret_cast<mirror::Object*>(field_value.value));
	} else {
	obj->SetFieldObject<false, kCheckTransaction>(field_offset,
	reinterpret_cast<mirror::Object*>(field_value.value));
	}
	break;
	default:
	LOG(FATAL) << "Unknown value kind " << static_cast<int>(field_value.kind);
	break;
	}
	}

	void Transaction::ObjectLog::VisitRoots(RootCallback* callback, void* arg) {
	for (auto it : field_values_) {
	FieldValue& field_value = it.second;
	if (field_value.kind == ObjectLog::kReference) {
	mirror::Object* obj =
	reinterpret_cast<mirror::Object*>(static_cast<uintptr_t>(field_value.value));
	if (obj != nullptr) {
	callback(&obj, arg, RootInfo(kRootUnknown));
	field_value.value = reinterpret_cast<uintptr_t>(obj);
	}
	}
	}
	}

	void Transaction::InternStringLog::Undo(InternTable* intern_table) {
	DCHECK(intern_table != nullptr);
	switch (string_op_) {
	case InternStringLog::kInsert: {
	switch (string_kind_) {
	case InternStringLog::kStrongString:
	intern_table->RemoveStrongFromTransaction(str_);
	break;
	case InternStringLog::kWeakString:
	intern_table->RemoveWeakFromTransaction(str_);
	break;
	default:
	LOG(FATAL) << "Unknown interned string kind";
	break;
	}
	break;
	}
	case InternStringLog::kRemove: {
	switch (string_kind_) {
	case InternStringLog::kStrongString:
	intern_table->InsertStrongFromTransaction(str_);
	break;
	case InternStringLog::kWeakString:
	intern_table->InsertWeakFromTransaction(str_);
	break;
	default:
	LOG(FATAL) << "Unknown interned string kind";
	break;
	}
	break;
	}
	default:
	LOG(FATAL) << "Unknown interned string op";
	break;
	}
	}

	void Transaction::InternStringLog::VisitRoots(RootCallback* callback, void* arg) {
	callback(reinterpret_cast<mirror::Object**>(&str_), arg, RootInfo(kRootInternedString));
	}

	void Transaction::ArrayLog::LogValue(size_t index, uint64_t value) {
	auto it = array_values_.find(index);
	if (it == array_values_.end()) {
	array_values_.insert(std::make_pair(index, value));
	}
	}

	void Transaction::ArrayLog::Undo(mirror::Array* array) {
	DCHECK(array != nullptr);
	DCHECK(array->IsArrayInstance());
	Primitive::Type type = array->GetClass()->GetComponentType()->GetPrimitiveType();
	for (auto it : array_values_) {
	UndoArrayWrite(array, type, it.first, it.second);
	}
	}

	void Transaction::ArrayLog::UndoArrayWrite(mirror::Array* array, Primitive::Type array_type,
	size_t index, uint64_t value) {
	// TODO We may want to abort a transaction while still being in transaction mode. In this case,
	// we'd need to disable the check.
	switch (array_type) {
	case Primitive::kPrimBoolean:
	array->AsBooleanArray()->SetWithoutChecks<false>(index, static_cast<uint8_t>(value));
	break;
	case Primitive::kPrimByte:
	array->AsByteArray()->SetWithoutChecks<false>(index, static_cast<int8_t>(value));
	break;
	case Primitive::kPrimChar:
	array->AsCharArray()->SetWithoutChecks<false>(index, static_cast<uint16_t>(value));
	break;
	case Primitive::kPrimShort:
	array->AsShortArray()->SetWithoutChecks<false>(index, static_cast<int16_t>(value));
	break;
	case Primitive::kPrimInt:
	array->AsIntArray()->SetWithoutChecks<false>(index, static_cast<int32_t>(value));
	break;
	case Primitive::kPrimFloat:
	array->AsFloatArray()->SetWithoutChecks<false>(index, static_cast<float>(value));
	break;
	case Primitive::kPrimLong:
	array->AsLongArray()->SetWithoutChecks<false>(index, static_cast<int64_t>(value));
	break;
	case Primitive::kPrimDouble:
	array->AsDoubleArray()->SetWithoutChecks<false>(index, static_cast<double>(value));
	break;
	case Primitive::kPrimNot:
	LOG(FATAL) << "ObjectArray should be treated as Object";
	break;
	default:
	LOG(FATAL) << "Unsupported type " << array_type;
	}
	}

	} // namespace art