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/*
* Copyright (C) 2015 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 "allocation_record.h"
#include "art_method-inl.h"
#include "base/enums.h"
#include "base/logging.h" // For VLOG
#include "base/stl_util.h"
#include "obj_ptr-inl.h"
#include "object_callbacks.h"
#include "stack.h"
#include "thread-inl.h" // For GetWeakRefAccessEnabled().
#include <android-base/properties.h>
namespace art {
namespace gc {
int32_t AllocRecordStackTraceElement::ComputeLineNumber() const {
DCHECK(method_ != nullptr);
int32_t line_number = method_->GetLineNumFromDexPC(dex_pc_);
if (line_number == -1 && !method_->IsProxyMethod()) {
// If we failed to map the dex pc to a line number, then most probably there is no debug info.
// Make the line_number same as the dex pc - it can be decoded later using a map file.
// See b/30183883 and b/228000954.
line_number = static_cast<int32_t>(dex_pc_);
}
return line_number;
}
const char* AllocRecord::GetClassDescriptor(std::string* storage) const {
// klass_ could contain null only if we implement class unloading.
return klass_.IsNull() ? "null" : klass_.Read()->GetDescriptor(storage);
}
void AllocRecordObjectMap::SetMaxStackDepth(size_t max_stack_depth) {
// Log fatal since this should already be checked when calling VMDebug.setAllocTrackerStackDepth.
CHECK_LE(max_stack_depth, kMaxSupportedStackDepth)
<< "Allocation record max stack depth is too large";
max_stack_depth_ = max_stack_depth;
}
AllocRecordObjectMap::~AllocRecordObjectMap() {
Clear();
}
void AllocRecordObjectMap::VisitRoots(RootVisitor* visitor) {
gc::Heap* const heap = Runtime::Current()->GetHeap();
// When we are compacting in userfaultfd GC, the class GC-roots are already
// updated in SweepAllocationRecords()->SweepClassObject().
if (heap->CurrentCollectorType() == gc::CollectorType::kCollectorTypeCMC
&& heap->MarkCompactCollector()->IsCompacting(Thread::Current())) {
return;
}
CHECK_LE(recent_record_max_, alloc_record_max_);
BufferedRootVisitor<kDefaultBufferedRootCount> buffered_visitor(visitor, RootInfo(kRootDebugger));
size_t count = recent_record_max_;
// Only visit the last recent_record_max_ number of allocation records in entries_ and mark the
// klass_ fields as strong roots.
for (auto it = entries_.rbegin(), end = entries_.rend(); it != end; ++it) {
AllocRecord& record = it->second;
if (count > 0) {
buffered_visitor.VisitRootIfNonNull(record.GetClassGcRoot());
--count;
}
// Visit all of the stack frames to make sure no methods in the stack traces get unloaded by
// class unloading.
for (size_t i = 0, depth = record.GetDepth(); i < depth; ++i) {
const AllocRecordStackTraceElement& element = record.StackElement(i);
DCHECK(element.GetMethod() != nullptr);
element.GetMethod()->VisitRoots(buffered_visitor, kRuntimePointerSize);
}
}
}
static inline void SweepClassObject(AllocRecord* record, IsMarkedVisitor* visitor)
REQUIRES_SHARED(Locks::mutator_lock_)
REQUIRES(Locks::alloc_tracker_lock_) {
GcRoot<mirror::Class>& klass = record->GetClassGcRoot();
// This does not need a read barrier because this is called by GC.
mirror::Object* old_object = klass.Read<kWithoutReadBarrier>();
if (old_object != nullptr) {
// The class object can become null if we implement class unloading.
// In that case we might still want to keep the class name string (not implemented).
mirror::Object* new_object = visitor->IsMarked(old_object);
DCHECK(new_object != nullptr);
if (UNLIKELY(old_object != new_object)) {
// We can't use AsClass() as it uses IsClass in a DCHECK, which expects
// the class' contents to be there. This is not the case in userfaultfd
// GC.
klass = GcRoot<mirror::Class>(ObjPtr<mirror::Class>::DownCast(new_object));
}
}
}
void AllocRecordObjectMap::SweepAllocationRecords(IsMarkedVisitor* visitor) {
VLOG(heap) << "Start SweepAllocationRecords()";
size_t count_deleted = 0, count_moved = 0, count = 0;
// Only the first (size - recent_record_max_) number of records can be deleted.
const size_t delete_bound = std::max(entries_.size(), recent_record_max_) - recent_record_max_;
for (auto it = entries_.begin(), end = entries_.end(); it != end;) {
++count;
// This does not need a read barrier because this is called by GC.
mirror::Object* old_object = it->first.Read<kWithoutReadBarrier>();
AllocRecord& record = it->second;
mirror::Object* new_object = old_object == nullptr ? nullptr : visitor->IsMarked(old_object);
if (new_object == nullptr) {
if (count > delete_bound) {
it->first = GcRoot<mirror::Object>(nullptr);
SweepClassObject(&record, visitor);
++it;
} else {
it = entries_.erase(it);
++count_deleted;
}
} else {
if (old_object != new_object) {
it->first = GcRoot<mirror::Object>(new_object);
++count_moved;
}
SweepClassObject(&record, visitor);
++it;
}
}
VLOG(heap) << "Deleted " << count_deleted << " allocation records";
VLOG(heap) << "Updated " << count_moved << " allocation records";
}
void AllocRecordObjectMap::AllowNewAllocationRecords() {
CHECK(!gUseReadBarrier);
allow_new_record_ = true;
new_record_condition_.Broadcast(Thread::Current());
}
void AllocRecordObjectMap::DisallowNewAllocationRecords() {
CHECK(!gUseReadBarrier);
allow_new_record_ = false;
}
void AllocRecordObjectMap::BroadcastForNewAllocationRecords() {
new_record_condition_.Broadcast(Thread::Current());
}
void AllocRecordObjectMap::SetAllocTrackingEnabled(bool enable) {
Thread* self = Thread::Current();
Heap* heap = Runtime::Current()->GetHeap();
if (enable) {
{
MutexLock mu(self, *Locks::alloc_tracker_lock_);
if (heap->IsAllocTrackingEnabled()) {
return; // Already enabled, bail.
}
AllocRecordObjectMap* records = heap->GetAllocationRecords();
if (records == nullptr) {
records = new AllocRecordObjectMap;
heap->SetAllocationRecords(records);
}
CHECK(records != nullptr);
records->SetMaxStackDepth(heap->GetAllocTrackerStackDepth());
size_t sz = sizeof(AllocRecordStackTraceElement) * records->max_stack_depth_ +
sizeof(AllocRecord) + sizeof(AllocRecordStackTrace);
LOG(INFO) << "Enabling alloc tracker (" << records->alloc_record_max_ << " entries of "
<< records->max_stack_depth_ << " frames, taking up to "
<< PrettySize(sz * records->alloc_record_max_) << ")";
}
Runtime::Current()->GetInstrumentation()->InstrumentQuickAllocEntryPoints();
{
MutexLock mu(self, *Locks::alloc_tracker_lock_);
heap->SetAllocTrackingEnabled(true);
}
} else {
// Delete outside of the critical section to avoid possible lock violations like the runtime
// shutdown lock.
{
MutexLock mu(self, *Locks::alloc_tracker_lock_);
if (!heap->IsAllocTrackingEnabled()) {
return; // Already disabled, bail.
}
heap->SetAllocTrackingEnabled(false);
LOG(INFO) << "Disabling alloc tracker";
AllocRecordObjectMap* records = heap->GetAllocationRecords();
records->Clear();
}
// If an allocation comes in before we uninstrument, we will safely drop it on the floor.
Runtime::Current()->GetInstrumentation()->UninstrumentQuickAllocEntryPoints();
}
}
void AllocRecordObjectMap::RecordAllocation(Thread* self,
ObjPtr<mirror::Object>* obj,
size_t byte_count) {
// Get stack trace outside of lock in case there are allocations during the stack walk.
// b/27858645.
AllocRecordStackTrace trace;
{
StackHandleScope<1> hs(self);
auto obj_wrapper = hs.NewHandleWrapper(obj);
StackVisitor::WalkStack(
[&](const art::StackVisitor* stack_visitor) REQUIRES_SHARED(Locks::mutator_lock_) {
if (trace.GetDepth() >= max_stack_depth_) {
return false;
}
ArtMethod* m = stack_visitor->GetMethod();
// m may be null if we have inlined methods of unresolved classes. b/27858645
if (m != nullptr && !m->IsRuntimeMethod()) {
m = m->GetInterfaceMethodIfProxy(kRuntimePointerSize);
trace.AddStackElement(AllocRecordStackTraceElement(m, stack_visitor->GetDexPc()));
}
return true;
},
self,
/* context= */ nullptr,
art::StackVisitor::StackWalkKind::kIncludeInlinedFrames);
}
MutexLock mu(self, *Locks::alloc_tracker_lock_);
Heap* const heap = Runtime::Current()->GetHeap();
if (!heap->IsAllocTrackingEnabled()) {
// In the process of shutting down recording, bail.
return;
}
// TODO Skip recording allocations associated with DDMS. This was a feature of the old debugger
// but when we switched to the JVMTI based debugger the feature was (unintentionally) broken.
// Since nobody seemed to really notice or care it might not be worth the trouble.
// Wait for GC's sweeping to complete and allow new records.
while (UNLIKELY((!gUseReadBarrier && !allow_new_record_) ||
(gUseReadBarrier && !self->GetWeakRefAccessEnabled()))) {
// Check and run the empty checkpoint before blocking so the empty checkpoint will work in the
// presence of threads blocking for weak ref access.
self->CheckEmptyCheckpointFromWeakRefAccess(Locks::alloc_tracker_lock_);
new_record_condition_.WaitHoldingLocks(self);
}
if (!heap->IsAllocTrackingEnabled()) {
// Return if the allocation tracking has been disabled while waiting for system weak access
// above.
return;
}
DCHECK_LE(Size(), alloc_record_max_);
// Erase extra unfilled elements.
trace.SetTid(self->GetTid());
// Add the record.
Put(obj->Ptr(), AllocRecord(byte_count, (*obj)->GetClass(), std::move(trace)));
DCHECK_LE(Size(), alloc_record_max_);
}
void AllocRecordObjectMap::Clear() {
entries_.clear();
}
AllocRecordObjectMap::AllocRecordObjectMap()
: new_record_condition_("New allocation record condition", *Locks::alloc_tracker_lock_) {}
} // namespace gc
} // namespace art