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/*
* Copyright (C) 2011 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 "intern_table.h"
#include <memory>
#include "dex/utf.h"
#include "gc/collector/garbage_collector.h"
#include "gc/space/image_space.h"
#include "gc/weak_root_state.h"
#include "gc_root-inl.h"
#include "image-inl.h"
#include "mirror/dex_cache-inl.h"
#include "mirror/object-inl.h"
#include "mirror/object_array-inl.h"
#include "mirror/string-inl.h"
#include "object_callbacks.h"
#include "scoped_thread_state_change-inl.h"
#include "thread.h"
namespace art {
InternTable::InternTable()
: log_new_roots_(false),
weak_intern_condition_("New intern condition", *Locks::intern_table_lock_),
weak_root_state_(gc::kWeakRootStateNormal) {
}
size_t InternTable::Size() const {
MutexLock mu(Thread::Current(), *Locks::intern_table_lock_);
return strong_interns_.Size() + weak_interns_.Size();
}
size_t InternTable::StrongSize() const {
MutexLock mu(Thread::Current(), *Locks::intern_table_lock_);
return strong_interns_.Size();
}
size_t InternTable::WeakSize() const {
MutexLock mu(Thread::Current(), *Locks::intern_table_lock_);
return weak_interns_.Size();
}
void InternTable::DumpForSigQuit(std::ostream& os) const {
os << "Intern table: " << StrongSize() << " strong; " << WeakSize() << " weak\n";
}
void InternTable::VisitRoots(RootVisitor* visitor, VisitRootFlags flags) {
MutexLock mu(Thread::Current(), *Locks::intern_table_lock_);
if ((flags & kVisitRootFlagAllRoots) != 0) {
strong_interns_.VisitRoots(visitor);
} else if ((flags & kVisitRootFlagNewRoots) != 0) {
for (auto& root : new_strong_intern_roots_) {
ObjPtr<mirror::String> old_ref = root.Read<kWithoutReadBarrier>();
root.VisitRoot(visitor, RootInfo(kRootInternedString));
ObjPtr<mirror::String> new_ref = root.Read<kWithoutReadBarrier>();
if (new_ref != old_ref) {
// The GC moved a root in the log. Need to search the strong interns and update the
// corresponding object. This is slow, but luckily for us, this may only happen with a
// concurrent moving GC.
strong_interns_.Remove(old_ref);
strong_interns_.Insert(new_ref);
}
}
}
if ((flags & kVisitRootFlagClearRootLog) != 0) {
new_strong_intern_roots_.clear();
}
if ((flags & kVisitRootFlagStartLoggingNewRoots) != 0) {
log_new_roots_ = true;
} else if ((flags & kVisitRootFlagStopLoggingNewRoots) != 0) {
log_new_roots_ = false;
}
// Note: we deliberately don't visit the weak_interns_ table and the immutable image roots.
}
ObjPtr<mirror::String> InternTable::LookupWeak(Thread* self, ObjPtr<mirror::String> s) {
MutexLock mu(self, *Locks::intern_table_lock_);
return LookupWeakLocked(s);
}
ObjPtr<mirror::String> InternTable::LookupStrong(Thread* self, ObjPtr<mirror::String> s) {
MutexLock mu(self, *Locks::intern_table_lock_);
return LookupStrongLocked(s);
}
ObjPtr<mirror::String> InternTable::LookupStrong(Thread* self,
uint32_t utf16_length,
const char* utf8_data) {
DCHECK_EQ(utf16_length, CountModifiedUtf8Chars(utf8_data));
Utf8String string(utf16_length,
utf8_data,
ComputeUtf16HashFromModifiedUtf8(utf8_data, utf16_length));
MutexLock mu(self, *Locks::intern_table_lock_);
return strong_interns_.Find(string);
}
ObjPtr<mirror::String> InternTable::LookupWeakLocked(ObjPtr<mirror::String> s) {
return weak_interns_.Find(s);
}
ObjPtr<mirror::String> InternTable::LookupStrongLocked(ObjPtr<mirror::String> s) {
return strong_interns_.Find(s);
}
void InternTable::AddNewTable() {
MutexLock mu(Thread::Current(), *Locks::intern_table_lock_);
weak_interns_.AddNewTable();
strong_interns_.AddNewTable();
}
ObjPtr<mirror::String> InternTable::InsertStrong(ObjPtr<mirror::String> s) {
Runtime* runtime = Runtime::Current();
if (runtime->IsActiveTransaction()) {
runtime->RecordStrongStringInsertion(s);
}
if (log_new_roots_) {
new_strong_intern_roots_.push_back(GcRoot<mirror::String>(s));
}
strong_interns_.Insert(s);
return s;
}
ObjPtr<mirror::String> InternTable::InsertWeak(ObjPtr<mirror::String> s) {
Runtime* runtime = Runtime::Current();
if (runtime->IsActiveTransaction()) {
runtime->RecordWeakStringInsertion(s);
}
weak_interns_.Insert(s);
return s;
}
void InternTable::RemoveStrong(ObjPtr<mirror::String> s) {
strong_interns_.Remove(s);
}
void InternTable::RemoveWeak(ObjPtr<mirror::String> s) {
Runtime* runtime = Runtime::Current();
if (runtime->IsActiveTransaction()) {
runtime->RecordWeakStringRemoval(s);
}
weak_interns_.Remove(s);
}
// Insert/remove methods used to undo changes made during an aborted transaction.
ObjPtr<mirror::String> InternTable::InsertStrongFromTransaction(ObjPtr<mirror::String> s) {
DCHECK(!Runtime::Current()->IsActiveTransaction());
return InsertStrong(s);
}
ObjPtr<mirror::String> InternTable::InsertWeakFromTransaction(ObjPtr<mirror::String> s) {
DCHECK(!Runtime::Current()->IsActiveTransaction());
return InsertWeak(s);
}
void InternTable::RemoveStrongFromTransaction(ObjPtr<mirror::String> s) {
DCHECK(!Runtime::Current()->IsActiveTransaction());
RemoveStrong(s);
}
void InternTable::RemoveWeakFromTransaction(ObjPtr<mirror::String> s) {
DCHECK(!Runtime::Current()->IsActiveTransaction());
RemoveWeak(s);
}
void InternTable::BroadcastForNewInterns() {
Thread* self = Thread::Current();
MutexLock mu(self, *Locks::intern_table_lock_);
weak_intern_condition_.Broadcast(self);
}
void InternTable::WaitUntilAccessible(Thread* self) {
Locks::intern_table_lock_->ExclusiveUnlock(self);
{
ScopedThreadSuspension sts(self, kWaitingWeakGcRootRead);
MutexLock mu(self, *Locks::intern_table_lock_);
while ((!kUseReadBarrier && weak_root_state_ == gc::kWeakRootStateNoReadsOrWrites) ||
(kUseReadBarrier && !self->GetWeakRefAccessEnabled())) {
weak_intern_condition_.Wait(self);
}
}
Locks::intern_table_lock_->ExclusiveLock(self);
}
ObjPtr<mirror::String> InternTable::Insert(ObjPtr<mirror::String> s,
bool is_strong,
bool holding_locks) {
if (s == nullptr) {
return nullptr;
}
Thread* const self = Thread::Current();
MutexLock mu(self, *Locks::intern_table_lock_);
if (kDebugLocking && !holding_locks) {
Locks::mutator_lock_->AssertSharedHeld(self);
CHECK_EQ(2u, self->NumberOfHeldMutexes()) << "may only safely hold the mutator lock";
}
while (true) {
if (holding_locks) {
if (!kUseReadBarrier) {
CHECK_EQ(weak_root_state_, gc::kWeakRootStateNormal);
} else {
CHECK(self->GetWeakRefAccessEnabled());
}
}
// Check the strong table for a match.
ObjPtr<mirror::String> strong = LookupStrongLocked(s);
if (strong != nullptr) {
return strong;
}
if ((!kUseReadBarrier && weak_root_state_ != gc::kWeakRootStateNoReadsOrWrites) ||
(kUseReadBarrier && self->GetWeakRefAccessEnabled())) {
break;
}
// weak_root_state_ is set to gc::kWeakRootStateNoReadsOrWrites in the GC pause but is only
// cleared after SweepSystemWeaks has completed. This is why we need to wait until it is
// cleared.
CHECK(!holding_locks);
StackHandleScope<1> hs(self);
auto h = hs.NewHandleWrapper(&s);
WaitUntilAccessible(self);
}
if (!kUseReadBarrier) {
CHECK_EQ(weak_root_state_, gc::kWeakRootStateNormal);
} else {
CHECK(self->GetWeakRefAccessEnabled());
}
// There is no match in the strong table, check the weak table.
ObjPtr<mirror::String> weak = LookupWeakLocked(s);
if (weak != nullptr) {
if (is_strong) {
// A match was found in the weak table. Promote to the strong table.
RemoveWeak(weak);
return InsertStrong(weak);
}
return weak;
}
// No match in the strong table or the weak table. Insert into the strong / weak table.
return is_strong ? InsertStrong(s) : InsertWeak(s);
}
ObjPtr<mirror::String> InternTable::InternStrong(int32_t utf16_length, const char* utf8_data) {
DCHECK(utf8_data != nullptr);
Thread* self = Thread::Current();
// Try to avoid allocation.
ObjPtr<mirror::String> s = LookupStrong(self, utf16_length, utf8_data);
if (s != nullptr) {
return s;
}
return InternStrong(mirror::String::AllocFromModifiedUtf8(
self, utf16_length, utf8_data));
}
ObjPtr<mirror::String> InternTable::InternStrong(const char* utf8_data) {
DCHECK(utf8_data != nullptr);
return InternStrong(mirror::String::AllocFromModifiedUtf8(Thread::Current(), utf8_data));
}
ObjPtr<mirror::String> InternTable::InternStrongImageString(ObjPtr<mirror::String> s) {
// May be holding the heap bitmap lock.
return Insert(s, true, true);
}
ObjPtr<mirror::String> InternTable::InternStrong(ObjPtr<mirror::String> s) {
return Insert(s, true, false);
}
ObjPtr<mirror::String> InternTable::InternWeak(ObjPtr<mirror::String> s) {
return Insert(s, false, false);
}
bool InternTable::ContainsWeak(ObjPtr<mirror::String> s) {
return LookupWeak(Thread::Current(), s) == s;
}
void InternTable::SweepInternTableWeaks(IsMarkedVisitor* visitor) {
MutexLock mu(Thread::Current(), *Locks::intern_table_lock_);
weak_interns_.SweepWeaks(visitor);
}
size_t InternTable::WriteToMemory(uint8_t* ptr) {
MutexLock mu(Thread::Current(), *Locks::intern_table_lock_);
return strong_interns_.WriteToMemory(ptr);
}
std::size_t InternTable::StringHashEquals::operator()(const GcRoot<mirror::String>& root) const {
if (kIsDebugBuild) {
Locks::mutator_lock_->AssertSharedHeld(Thread::Current());
}
// An additional cast to prevent undesired sign extension.
return static_cast<size_t>(
static_cast<uint32_t>(root.Read<kWithoutReadBarrier>()->GetHashCode()));
}
bool InternTable::StringHashEquals::operator()(const GcRoot<mirror::String>& a,
const GcRoot<mirror::String>& b) const {
if (kIsDebugBuild) {
Locks::mutator_lock_->AssertSharedHeld(Thread::Current());
}
return a.Read<kWithoutReadBarrier>()->Equals(b.Read<kWithoutReadBarrier>());
}
bool InternTable::StringHashEquals::operator()(const GcRoot<mirror::String>& a,
const Utf8String& b) const {
if (kIsDebugBuild) {
Locks::mutator_lock_->AssertSharedHeld(Thread::Current());
}
ObjPtr<mirror::String> a_string = a.Read<kWithoutReadBarrier>();
uint32_t a_length = static_cast<uint32_t>(a_string->GetLength());
if (a_length != b.GetUtf16Length()) {
return false;
}
if (a_string->IsCompressed()) {
size_t b_byte_count = strlen(b.GetUtf8Data());
size_t b_utf8_length = CountModifiedUtf8Chars(b.GetUtf8Data(), b_byte_count);
// Modified UTF-8 single byte character range is 0x01 .. 0x7f
// The string compression occurs on regular ASCII with same exact range,
// not on extended ASCII which up to 0xff
const bool is_b_regular_ascii = (b_byte_count == b_utf8_length);
if (is_b_regular_ascii) {
return memcmp(b.GetUtf8Data(),
a_string->GetValueCompressed(), a_length * sizeof(uint8_t)) == 0;
} else {
return false;
}
} else {
const uint16_t* a_value = a_string->GetValue();
return CompareModifiedUtf8ToUtf16AsCodePointValues(b.GetUtf8Data(), a_value, a_length) == 0;
}
}
size_t InternTable::Table::WriteToMemory(uint8_t* ptr) {
if (tables_.empty()) {
return 0;
}
UnorderedSet* table_to_write;
UnorderedSet combined;
if (tables_.size() > 1) {
table_to_write = &combined;
for (UnorderedSet& table : tables_) {
for (GcRoot<mirror::String>& string : table) {
combined.insert(string);
}
}
} else {
table_to_write = &tables_.back();
}
return table_to_write->WriteToMemory(ptr);
}
void InternTable::Table::Remove(ObjPtr<mirror::String> s) {
for (UnorderedSet& table : tables_) {
auto it = table.find(GcRoot<mirror::String>(s));
if (it != table.end()) {
table.erase(it);
return;
}
}
LOG(FATAL) << "Attempting to remove non-interned string " << s->ToModifiedUtf8();
}
ObjPtr<mirror::String> InternTable::Table::Find(ObjPtr<mirror::String> s) {
Locks::intern_table_lock_->AssertHeld(Thread::Current());
for (UnorderedSet& table : tables_) {
auto it = table.find(GcRoot<mirror::String>(s));
if (it != table.end()) {
return it->Read();
}
}
return nullptr;
}
ObjPtr<mirror::String> InternTable::Table::Find(const Utf8String& string) {
Locks::intern_table_lock_->AssertHeld(Thread::Current());
for (UnorderedSet& table : tables_) {
auto it = table.find(string);
if (it != table.end()) {
return it->Read();
}
}
return nullptr;
}
void InternTable::Table::AddNewTable() {
tables_.push_back(UnorderedSet());
}
void InternTable::Table::Insert(ObjPtr<mirror::String> s) {
// Always insert the last table, the image tables are before and we avoid inserting into these
// to prevent dirty pages.
DCHECK(!tables_.empty());
tables_.back().insert(GcRoot<mirror::String>(s));
}
void InternTable::Table::VisitRoots(RootVisitor* visitor) {
BufferedRootVisitor<kDefaultBufferedRootCount> buffered_visitor(
visitor, RootInfo(kRootInternedString));
for (UnorderedSet& table : tables_) {
for (auto& intern : table) {
buffered_visitor.VisitRoot(intern);
}
}
}
void InternTable::Table::SweepWeaks(IsMarkedVisitor* visitor) {
for (UnorderedSet& table : tables_) {
SweepWeaks(&table, visitor);
}
}
void InternTable::Table::SweepWeaks(UnorderedSet* set, IsMarkedVisitor* visitor) {
for (auto it = set->begin(), end = set->end(); it != end;) {
// This does not need a read barrier because this is called by GC.
mirror::Object* object = it->Read<kWithoutReadBarrier>();
mirror::Object* new_object = visitor->IsMarked(object);
if (new_object == nullptr) {
it = set->erase(it);
} else {
*it = GcRoot<mirror::String>(new_object->AsString());
++it;
}
}
}
size_t InternTable::Table::Size() const {
return std::accumulate(tables_.begin(),
tables_.end(),
0U,
[](size_t sum, const UnorderedSet& set) {
return sum + set.size();
});
}
void InternTable::ChangeWeakRootState(gc::WeakRootState new_state) {
MutexLock mu(Thread::Current(), *Locks::intern_table_lock_);
ChangeWeakRootStateLocked(new_state);
}
void InternTable::ChangeWeakRootStateLocked(gc::WeakRootState new_state) {
CHECK(!kUseReadBarrier);
weak_root_state_ = new_state;
if (new_state != gc::kWeakRootStateNoReadsOrWrites) {
weak_intern_condition_.Broadcast(Thread::Current());
}
}
InternTable::Table::Table() {
Runtime* const runtime = Runtime::Current();
// Initial table.
tables_.push_back(UnorderedSet());
tables_.back().SetLoadFactor(runtime->GetHashTableMinLoadFactor(),
runtime->GetHashTableMaxLoadFactor());
}
} // namespace art