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/*
* Copyright (C) 2013 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 "object_registry.h"
#include "handle_scope-inl.h"
#include "jni_internal.h"
#include "mirror/class.h"
#include "scoped_thread_state_change.h"
namespace art {
std::ostream& operator<<(std::ostream& os, const ObjectRegistryEntry& rhs) {
os << "ObjectRegistryEntry[" << rhs.jni_reference_type
<< ",reference=" << rhs.jni_reference
<< ",count=" << rhs.reference_count
<< ",id=" << rhs.id << "]";
return os;
}
ObjectRegistry::ObjectRegistry()
: lock_("ObjectRegistry lock", kJdwpObjectRegistryLock), next_id_(1) {
}
JDWP::RefTypeId ObjectRegistry::AddRefType(mirror::Class* c) {
return Add(c);
}
JDWP::RefTypeId ObjectRegistry::AddRefType(Handle<mirror::Class> c_h) {
return Add(c_h);
}
JDWP::ObjectId ObjectRegistry::Add(mirror::Object* o) {
if (o == nullptr) {
return 0;
}
Thread* const self = Thread::Current();
StackHandleScope<1> hs(self);
return InternalAdd(hs.NewHandle(o));
}
// Template instantiations must be declared below.
template<class T>
JDWP::ObjectId ObjectRegistry::Add(Handle<T> obj_h) {
if (obj_h.Get() == nullptr) {
return 0;
}
return InternalAdd(obj_h);
}
// Explicit template instantiation.
template
SHARED_REQUIRES(Locks::mutator_lock_)
REQUIRES(!Locks::thread_list_lock_, !Locks::thread_suspend_count_lock_)
JDWP::ObjectId ObjectRegistry::Add(Handle<mirror::Object> obj_h);
template
SHARED_REQUIRES(Locks::mutator_lock_)
REQUIRES(!Locks::thread_list_lock_, !Locks::thread_suspend_count_lock_)
JDWP::ObjectId ObjectRegistry::Add(Handle<mirror::Throwable> obj_h);
template<class T>
JDWP::ObjectId ObjectRegistry::InternalAdd(Handle<T> obj_h) {
CHECK(obj_h.Get() != nullptr);
Thread* const self = Thread::Current();
self->AssertNoPendingException();
// Object::IdentityHashCode may cause these locks to be held so check we do not already
// hold them.
Locks::thread_list_lock_->AssertNotHeld(self);
Locks::thread_suspend_count_lock_->AssertNotHeld(self);
// Call IdentityHashCode here to avoid a lock level violation between lock_ and monitor_lock.
int32_t identity_hash_code = obj_h->IdentityHashCode();
ScopedObjectAccessUnchecked soa(self);
MutexLock mu(soa.Self(), lock_);
ObjectRegistryEntry* entry = nullptr;
if (ContainsLocked(soa.Self(), obj_h.Get(), identity_hash_code, &entry)) {
// This object was already in our map.
++entry->reference_count;
} else {
entry = new ObjectRegistryEntry;
entry->jni_reference_type = JNIWeakGlobalRefType;
entry->jni_reference = nullptr;
entry->reference_count = 0;
entry->id = 0;
entry->identity_hash_code = identity_hash_code;
object_to_entry_.insert(std::make_pair(identity_hash_code, entry));
// This object isn't in the registry yet, so add it.
JNIEnv* env = soa.Env();
jobject local_reference = soa.AddLocalReference<jobject>(obj_h.Get());
entry->jni_reference_type = JNIWeakGlobalRefType;
entry->jni_reference = env->NewWeakGlobalRef(local_reference);
entry->reference_count = 1;
entry->id = next_id_++;
id_to_entry_.Put(entry->id, entry);
env->DeleteLocalRef(local_reference);
}
return entry->id;
}
bool ObjectRegistry::ContainsLocked(Thread* self, mirror::Object* o, int32_t identity_hash_code,
ObjectRegistryEntry** out_entry) {
DCHECK(o != nullptr);
for (auto it = object_to_entry_.lower_bound(identity_hash_code), end = object_to_entry_.end();
it != end && it->first == identity_hash_code; ++it) {
ObjectRegistryEntry* entry = it->second;
if (o == self->DecodeJObject(entry->jni_reference)) {
if (out_entry != nullptr) {
*out_entry = entry;
}
return true;
}
}
return false;
}
void ObjectRegistry::Clear() {
Thread* const self = Thread::Current();
// We must not hold the mutator lock exclusively if we want to delete weak global
// references. Otherwise this can lead to a deadlock with a running GC:
// 1. GC thread disables access to weak global references, then releases
// mutator lock.
// 2. JDWP thread takes mutator lock exclusively after suspending all
// threads.
// 3. GC thread waits for shared mutator lock which is held by JDWP
// thread.
// 4. JDWP thread clears weak global references but need to wait for GC
// thread to re-enable access to them.
Locks::mutator_lock_->AssertNotExclusiveHeld(self);
MutexLock mu(self, lock_);
VLOG(jdwp) << "Object registry contained " << object_to_entry_.size() << " entries";
// Delete all the JNI references.
JNIEnv* env = self->GetJniEnv();
for (const auto& pair : object_to_entry_) {
const ObjectRegistryEntry* entry = pair.second;
if (entry->jni_reference_type == JNIWeakGlobalRefType) {
env->DeleteWeakGlobalRef(entry->jni_reference);
} else {
env->DeleteGlobalRef(entry->jni_reference);
}
delete entry;
}
// Clear the maps.
object_to_entry_.clear();
id_to_entry_.clear();
}
mirror::Object* ObjectRegistry::InternalGet(JDWP::ObjectId id, JDWP::JdwpError* error) {
Thread* self = Thread::Current();
MutexLock mu(self, lock_);
auto it = id_to_entry_.find(id);
if (it == id_to_entry_.end()) {
*error = JDWP::ERR_INVALID_OBJECT;
return nullptr;
}
ObjectRegistryEntry& entry = *it->second;
*error = JDWP::ERR_NONE;
return self->DecodeJObject(entry.jni_reference);
}
jobject ObjectRegistry::GetJObject(JDWP::ObjectId id) {
if (id == 0) {
return nullptr;
}
Thread* self = Thread::Current();
MutexLock mu(self, lock_);
auto it = id_to_entry_.find(id);
CHECK(it != id_to_entry_.end()) << id;
ObjectRegistryEntry& entry = *it->second;
return entry.jni_reference;
}
void ObjectRegistry::DisableCollection(JDWP::ObjectId id) {
Thread* self = Thread::Current();
MutexLock mu(self, lock_);
auto it = id_to_entry_.find(id);
CHECK(it != id_to_entry_.end());
Promote(*it->second);
}
void ObjectRegistry::EnableCollection(JDWP::ObjectId id) {
Thread* self = Thread::Current();
MutexLock mu(self, lock_);
auto it = id_to_entry_.find(id);
CHECK(it != id_to_entry_.end());
Demote(*it->second);
}
void ObjectRegistry::Demote(ObjectRegistryEntry& entry) {
if (entry.jni_reference_type == JNIGlobalRefType) {
Thread* self = Thread::Current();
JNIEnv* env = self->GetJniEnv();
jobject global = entry.jni_reference;
entry.jni_reference = env->NewWeakGlobalRef(entry.jni_reference);
entry.jni_reference_type = JNIWeakGlobalRefType;
env->DeleteGlobalRef(global);
}
}
void ObjectRegistry::Promote(ObjectRegistryEntry& entry) {
if (entry.jni_reference_type == JNIWeakGlobalRefType) {
Thread* self = Thread::Current();
JNIEnv* env = self->GetJniEnv();
jobject weak = entry.jni_reference;
entry.jni_reference = env->NewGlobalRef(entry.jni_reference);
entry.jni_reference_type = JNIGlobalRefType;
env->DeleteWeakGlobalRef(weak);
}
}
bool ObjectRegistry::IsCollected(JDWP::ObjectId id) {
Thread* self = Thread::Current();
MutexLock mu(self, lock_);
auto it = id_to_entry_.find(id);
CHECK(it != id_to_entry_.end());
ObjectRegistryEntry& entry = *it->second;
if (entry.jni_reference_type == JNIWeakGlobalRefType) {
JNIEnv* env = self->GetJniEnv();
return env->IsSameObject(entry.jni_reference, nullptr); // Has the jweak been collected?
} else {
return false; // We hold a strong reference, so we know this is live.
}
}
void ObjectRegistry::DisposeObject(JDWP::ObjectId id, uint32_t reference_count) {
Thread* self = Thread::Current();
MutexLock mu(self, lock_);
auto it = id_to_entry_.find(id);
if (it == id_to_entry_.end()) {
return;
}
ObjectRegistryEntry* entry = it->second;
entry->reference_count -= reference_count;
if (entry->reference_count <= 0) {
JNIEnv* env = self->GetJniEnv();
// Erase the object from the maps. Note object may be null if it's
// a weak ref and the GC has cleared it.
int32_t hash_code = entry->identity_hash_code;
for (auto inner_it = object_to_entry_.lower_bound(hash_code), end = object_to_entry_.end();
inner_it != end && inner_it->first == hash_code; ++inner_it) {
if (entry == inner_it->second) {
object_to_entry_.erase(inner_it);
break;
}
}
if (entry->jni_reference_type == JNIWeakGlobalRefType) {
env->DeleteWeakGlobalRef(entry->jni_reference);
} else {
env->DeleteGlobalRef(entry->jni_reference);
}
id_to_entry_.erase(id);
delete entry;
}
}
} // namespace art