runtime/vm/thread.cc

// Copyright (c) 2015, the Dart project authors.  Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.

#include "vm/thread.h"

#include "vm/dart_api_state.h"
#include "vm/growable_array.h"
#include "vm/isolate.h"
#include "vm/json_stream.h"
#include "vm/lockers.h"
#include "vm/log.h"
#include "vm/message_handler.h"
#include "vm/native_entry.h"
#include "vm/object.h"
#include "vm/os_thread.h"
#include "vm/profiler.h"
#include "vm/runtime_entry.h"
#include "vm/stub_code.h"
#include "vm/symbols.h"
#include "vm/thread_interrupter.h"
#include "vm/thread_registry.h"
#include "vm/timeline.h"
#include "vm/zone.h"

namespace dart {

DECLARE_FLAG(bool, trace_service);
DECLARE_FLAG(bool, trace_service_verbose);

Thread::~Thread() {
  // We should cleanly exit any isolate before destruction.
  ASSERT(isolate_ == NULL);
  ASSERT(store_buffer_block_ == NULL);
  ASSERT(marking_stack_block_ == NULL);
#if !defined(DART_PRECOMPILED_RUNTIME)
  delete interpreter_;
  interpreter_ = nullptr;
#endif
  // There should be no top api scopes at this point.
  ASSERT(api_top_scope() == NULL);
  // Delete the resusable api scope if there is one.
  if (api_reusable_scope_) {
    delete api_reusable_scope_;
    api_reusable_scope_ = NULL;
  }
  delete thread_lock_;
  thread_lock_ = NULL;
}

#if defined(DEBUG)
#define REUSABLE_HANDLE_SCOPE_INIT(object)                                     \
  reusable_##object##_handle_scope_active_(false),
#else
#define REUSABLE_HANDLE_SCOPE_INIT(object)
#endif  // defined(DEBUG)

#define REUSABLE_HANDLE_INITIALIZERS(object) object##_handle_(NULL),

Thread::Thread(Isolate* isolate)
    : BaseThread(false),
      stack_limit_(0),
      stack_overflow_flags_(0),
      write_barrier_mask_(RawObject::kGenerationalBarrierMask),
      isolate_(NULL),
      heap_(NULL),
      top_(0),
      end_(0),
      top_exit_frame_info_(0),
      store_buffer_block_(NULL),
      marking_stack_block_(NULL),
      vm_tag_(0),
      async_stack_trace_(StackTrace::null()),
      unboxed_int64_runtime_arg_(0),
      active_exception_(Object::null()),
      active_stacktrace_(Object::null()),
      resume_pc_(0),
      task_kind_(kUnknownTask),
      dart_stream_(NULL),
      os_thread_(NULL),
      thread_lock_(new Monitor()),
      zone_(NULL),
      current_zone_capacity_(0),
      zone_high_watermark_(0),
      api_reusable_scope_(NULL),
      api_top_scope_(NULL),
      top_resource_(NULL),
      long_jump_base_(NULL),
      no_callback_scope_depth_(0),
#if defined(DEBUG)
      top_handle_scope_(NULL),
      no_safepoint_scope_depth_(0),
#endif
      reusable_handles_(),
      saved_stack_limit_(0),
      defer_oob_messages_count_(0),
      deferred_interrupts_mask_(0),
      deferred_interrupts_(0),
      stack_overflow_count_(0),
      bump_allocate_(false),
      hierarchy_info_(NULL),
      type_usage_info_(NULL),
      pending_functions_(GrowableObjectArray::null()),
      sticky_error_(Error::null()),
      REUSABLE_HANDLE_LIST(REUSABLE_HANDLE_INITIALIZERS)
          REUSABLE_HANDLE_LIST(REUSABLE_HANDLE_SCOPE_INIT) safepoint_state_(0),
      execution_state_(kThreadInNative),
#if defined(USING_SAFE_STACK)
      saved_safestack_limit_(0),
#endif
#if !defined(DART_PRECOMPILED_RUNTIME)
      interpreter_(nullptr),
#endif
      next_(NULL) {
#if !defined(PRODUCT)
  dart_stream_ = Timeline::GetDartStream();
  ASSERT(dart_stream_ != NULL);
#endif
#define DEFAULT_INIT(type_name, member_name, init_expr, default_init_value)    \
  member_name = default_init_value;
  CACHED_CONSTANTS_LIST(DEFAULT_INIT)
#undef DEFAULT_INIT

#if defined(TARGET_ARCH_ARM) || defined(TARGET_ARCH_ARM64) ||                  \
    defined(TARGET_ARCH_X64)
  for (intptr_t i = 0; i < kNumberOfDartAvailableCpuRegs; ++i) {
    write_barrier_wrappers_entry_points_[i] = 0;
  }
#endif

#define DEFAULT_INIT(name) name##_entry_point_ = 0;
  RUNTIME_ENTRY_LIST(DEFAULT_INIT)
#undef DEFAULT_INIT

#define DEFAULT_INIT(returntype, name, ...) name##_entry_point_ = 0;
  LEAF_RUNTIME_ENTRY_LIST(DEFAULT_INIT)
#undef DEFAULT_INIT

  // We cannot initialize the VM constants here for the vm isolate thread
  // due to boot strapping issues.
  if ((Dart::vm_isolate() != NULL) && (isolate != Dart::vm_isolate())) {
    InitVMConstants();
  }

  // This thread should not yet own any zones. If it does, we need to make sure
  // we've accounted for any memory it has already allocated.
  if (zone_ == NULL) {
    ASSERT(current_zone_capacity_ == 0);
  } else {
    Zone* current = zone_;
    uintptr_t total_zone_capacity = 0;
    while (current != NULL) {
      total_zone_capacity += current->CapacityInBytes();
      current = current->previous();
    }
    ASSERT(current_zone_capacity_ == total_zone_capacity);
  }
}

static const double double_nan_constant = NAN;

static const struct ALIGN16 {
  uint64_t a;
  uint64_t b;
} double_negate_constant = {0x8000000000000000LL, 0x8000000000000000LL};

static const struct ALIGN16 {
  uint64_t a;
  uint64_t b;
} double_abs_constant = {0x7FFFFFFFFFFFFFFFLL, 0x7FFFFFFFFFFFFFFFLL};

static const struct ALIGN16 {
  uint32_t a;
  uint32_t b;
  uint32_t c;
  uint32_t d;
} float_not_constant = {0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF};

static const struct ALIGN16 {
  uint32_t a;
  uint32_t b;
  uint32_t c;
  uint32_t d;
} float_negate_constant = {0x80000000, 0x80000000, 0x80000000, 0x80000000};

static const struct ALIGN16 {
  uint32_t a;
  uint32_t b;
  uint32_t c;
  uint32_t d;
} float_absolute_constant = {0x7FFFFFFF, 0x7FFFFFFF, 0x7FFFFFFF, 0x7FFFFFFF};

static const struct ALIGN16 {
  uint32_t a;
  uint32_t b;
  uint32_t c;
  uint32_t d;
} float_zerow_constant = {0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF, 0x00000000};

void Thread::InitVMConstants() {
#define ASSERT_VM_HEAP(type_name, member_name, init_expr, default_init_value)  \
  ASSERT((init_expr)->IsOldObject());
  CACHED_VM_OBJECTS_LIST(ASSERT_VM_HEAP)
#undef ASSERT_VM_HEAP

#define INIT_VALUE(type_name, member_name, init_expr, default_init_value)      \
  ASSERT(member_name == default_init_value);                                   \
  member_name = (init_expr);
  CACHED_CONSTANTS_LIST(INIT_VALUE)
#undef INIT_VALUE

#if defined(TARGET_ARCH_ARM) || defined(TARGET_ARCH_ARM64) ||                  \
    defined(TARGET_ARCH_X64)
  for (intptr_t i = 0; i < kNumberOfDartAvailableCpuRegs; ++i) {
    write_barrier_wrappers_entry_points_[i] =
        StubCode::WriteBarrierWrappers().EntryPoint() +
        i * kStoreBufferWrapperSize;
  }
#endif

#define INIT_VALUE(name)                                                       \
  ASSERT(name##_entry_point_ == 0);                                            \
  name##_entry_point_ = k##name##RuntimeEntry.GetEntryPoint();
  RUNTIME_ENTRY_LIST(INIT_VALUE)
#undef INIT_VALUE

#define INIT_VALUE(returntype, name, ...)                                      \
  ASSERT(name##_entry_point_ == 0);                                            \
  name##_entry_point_ = k##name##RuntimeEntry.GetEntryPoint();
  LEAF_RUNTIME_ENTRY_LIST(INIT_VALUE)
#undef INIT_VALUE

// Setup the thread specific reusable handles.
#define REUSABLE_HANDLE_ALLOCATION(object)                                     \
  this->object##_handle_ = this->AllocateReusableHandle<object>();
  REUSABLE_HANDLE_LIST(REUSABLE_HANDLE_ALLOCATION)
#undef REUSABLE_HANDLE_ALLOCATION
}

#ifndef PRODUCT
// Collect information about each individual zone associated with this thread.
void Thread::PrintJSON(JSONStream* stream) const {
  JSONObject jsobj(stream);
  jsobj.AddProperty("type", "_Thread");
  jsobj.AddPropertyF("id", "threads/%" Pd "",
                     OSThread::ThreadIdToIntPtr(os_thread()->trace_id()));
  jsobj.AddProperty("kind", TaskKindToCString(task_kind()));
  jsobj.AddPropertyF("_zoneHighWatermark", "%" Pu "", zone_high_watermark_);
  jsobj.AddPropertyF("_zoneCapacity", "%" Pu "", current_zone_capacity_);
}
#endif

RawGrowableObjectArray* Thread::pending_functions() {
  if (pending_functions_ == GrowableObjectArray::null()) {
    pending_functions_ = GrowableObjectArray::New(Heap::kOld);
  }
  return pending_functions_;
}

void Thread::clear_pending_functions() {
  pending_functions_ = GrowableObjectArray::null();
}

void Thread::set_active_exception(const Object& value) {
  active_exception_ = value.raw();
}

void Thread::set_active_stacktrace(const Object& value) {
  active_stacktrace_ = value.raw();
}

RawError* Thread::sticky_error() const {
  return sticky_error_;
}

void Thread::set_sticky_error(const Error& value) {
  ASSERT(!value.IsNull());
  sticky_error_ = value.raw();
}

void Thread::clear_sticky_error() {
  sticky_error_ = Error::null();
}

RawError* Thread::get_and_clear_sticky_error() {
  NoSafepointScope nss;
  RawError* return_value = sticky_error_;
  sticky_error_ = Error::null();
  return return_value;
}

const char* Thread::TaskKindToCString(TaskKind kind) {
  switch (kind) {
    case kUnknownTask:
      return "kUnknownTask";
    case kMutatorTask:
      return "kMutatorTask";
    case kCompilerTask:
      return "kCompilerTask";
    case kSweeperTask:
      return "kSweeperTask";
    case kMarkerTask:
      return "kMarkerTask";
    default:
      UNREACHABLE();
      return "";
  }
}

RawStackTrace* Thread::async_stack_trace() const {
  return async_stack_trace_;
}

void Thread::set_async_stack_trace(const StackTrace& stack_trace) {
  ASSERT(!stack_trace.IsNull());
  async_stack_trace_ = stack_trace.raw();
}

void Thread::set_raw_async_stack_trace(RawStackTrace* raw_stack_trace) {
  async_stack_trace_ = raw_stack_trace;
}

void Thread::clear_async_stack_trace() {
  async_stack_trace_ = StackTrace::null();
}

bool Thread::EnterIsolate(Isolate* isolate) {
  const bool kIsMutatorThread = true;
  Thread* thread = isolate->ScheduleThread(kIsMutatorThread);
  if (thread != NULL) {
    ASSERT(thread->store_buffer_block_ == NULL);
    thread->task_kind_ = kMutatorTask;
    thread->StoreBufferAcquire();
    if (isolate->marking_stack() != NULL) {
      // Concurrent mark in progress. Enable barrier for this thread.
      thread->MarkingStackAcquire();
    }
    return true;
  }
  return false;
}

void Thread::ExitIsolate() {
  Thread* thread = Thread::Current();
  ASSERT(thread != NULL && thread->IsMutatorThread());
  DEBUG_ASSERT(!thread->IsAnyReusableHandleScopeActive());
  thread->task_kind_ = kUnknownTask;
  Isolate* isolate = thread->isolate();
  ASSERT(isolate != NULL);
  ASSERT(thread->execution_state() == Thread::kThreadInVM);
  // Clear since GC will not visit the thread once it is unscheduled.
  thread->ClearReusableHandles();
  if (thread->is_marking()) {
    thread->MarkingStackRelease();
  }
  thread->StoreBufferRelease();
  if (isolate->is_runnable()) {
    thread->set_vm_tag(VMTag::kIdleTagId);
  } else {
    thread->set_vm_tag(VMTag::kLoadWaitTagId);
  }
  const bool kIsMutatorThread = true;
  isolate->UnscheduleThread(thread, kIsMutatorThread);
}

bool Thread::EnterIsolateAsHelper(Isolate* isolate,
                                  TaskKind kind,
                                  bool bypass_safepoint) {
  ASSERT(kind != kMutatorTask);
  const bool kIsNotMutatorThread = false;
  Thread* thread =
      isolate->ScheduleThread(kIsNotMutatorThread, bypass_safepoint);
  if (thread != NULL) {
    ASSERT(thread->store_buffer_block_ == NULL);
    // TODO(koda): Use StoreBufferAcquire once we properly flush
    // before Scavenge.
    thread->store_buffer_block_ =
        thread->isolate()->store_buffer()->PopEmptyBlock();
    if (isolate->marking_stack() != NULL) {
      // Concurrent mark in progress. Enable barrier for this thread.
      thread->MarkingStackAcquire();
    }
    // This thread should not be the main mutator.
    thread->task_kind_ = kind;
    ASSERT(!thread->IsMutatorThread());
    return true;
  }
  return false;
}

void Thread::ExitIsolateAsHelper(bool bypass_safepoint) {
  Thread* thread = Thread::Current();
  ASSERT(thread != NULL);
  ASSERT(!thread->IsMutatorThread());
  ASSERT(thread->execution_state() == Thread::kThreadInVM);
  thread->task_kind_ = kUnknownTask;
  // Clear since GC will not visit the thread once it is unscheduled.
  thread->ClearReusableHandles();
  if (thread->is_marking()) {
    thread->MarkingStackRelease();
  }
  thread->StoreBufferRelease();
  Isolate* isolate = thread->isolate();
  ASSERT(isolate != NULL);
  const bool kIsNotMutatorThread = false;
  isolate->UnscheduleThread(thread, kIsNotMutatorThread, bypass_safepoint);
}

void Thread::ReleaseStoreBuffer() {
  ASSERT(IsAtSafepoint());
  // Prevent scheduling another GC by ignoring the threshold.
  ASSERT(store_buffer_block_ != NULL);
  StoreBufferRelease(StoreBuffer::kIgnoreThreshold);
  // Make sure to get an *empty* block; the isolate needs all entries
  // at GC time.
  // TODO(koda): Replace with an epilogue (PrepareAfterGC) that acquires.
  store_buffer_block_ = isolate()->store_buffer()->PopEmptyBlock();
}

void Thread::SetStackLimit(uword limit) {
  // The thread setting the stack limit is not necessarily the thread which
  // the stack limit is being set on.
  MonitorLocker ml(thread_lock_);
  if (stack_limit_ == saved_stack_limit_) {
    // No interrupt pending, set stack_limit_ too.
    stack_limit_ = limit;
  }
  saved_stack_limit_ = limit;
}

void Thread::ClearStackLimit() {
  SetStackLimit(~static_cast<uword>(0));
}

void Thread::ScheduleInterrupts(uword interrupt_bits) {
  MonitorLocker ml(thread_lock_);
  ScheduleInterruptsLocked(interrupt_bits);
}

void Thread::ScheduleInterruptsLocked(uword interrupt_bits) {
  ASSERT(thread_lock_->IsOwnedByCurrentThread());
  ASSERT((interrupt_bits & ~kInterruptsMask) == 0);  // Must fit in mask.

  // Check to see if any of the requested interrupts should be deferred.
  uword defer_bits = interrupt_bits & deferred_interrupts_mask_;
  if (defer_bits != 0) {
    deferred_interrupts_ |= defer_bits;
    interrupt_bits &= ~deferred_interrupts_mask_;
    if (interrupt_bits == 0) {
      return;
    }
  }

  if (stack_limit_ == saved_stack_limit_) {
    stack_limit_ = kInterruptStackLimit & ~kInterruptsMask;
  }
  stack_limit_ |= interrupt_bits;
}

uword Thread::GetAndClearInterrupts() {
  MonitorLocker ml(thread_lock_);
  if (stack_limit_ == saved_stack_limit_) {
    return 0;  // No interrupt was requested.
  }
  uword interrupt_bits = stack_limit_ & kInterruptsMask;
  stack_limit_ = saved_stack_limit_;
  return interrupt_bits;
}

bool Thread::ZoneIsOwnedByThread(Zone* zone) const {
  ASSERT(zone != NULL);
  Zone* current = zone_;
  while (current != NULL) {
    if (current == zone) {
      return true;
    }
    current = current->previous();
  }
  return false;
}

void Thread::DeferOOBMessageInterrupts() {
  MonitorLocker ml(thread_lock_);
  defer_oob_messages_count_++;
  if (defer_oob_messages_count_ > 1) {
    // OOB message interrupts are already deferred.
    return;
  }
  ASSERT(deferred_interrupts_mask_ == 0);
  deferred_interrupts_mask_ = kMessageInterrupt;

  if (stack_limit_ != saved_stack_limit_) {
    // Defer any interrupts which are currently pending.
    deferred_interrupts_ = stack_limit_ & deferred_interrupts_mask_;

    // Clear deferrable interrupts, if present.
    stack_limit_ &= ~deferred_interrupts_mask_;

    if ((stack_limit_ & kInterruptsMask) == 0) {
      // No other pending interrupts.  Restore normal stack limit.
      stack_limit_ = saved_stack_limit_;
    }
  }
  if (FLAG_trace_service && FLAG_trace_service_verbose) {
    OS::PrintErr("[+%" Pd64 "ms] Isolate %s deferring OOB interrupts\n",
                 Dart::UptimeMillis(), isolate()->name());
  }
}

void Thread::RestoreOOBMessageInterrupts() {
  MonitorLocker ml(thread_lock_);
  defer_oob_messages_count_--;
  if (defer_oob_messages_count_ > 0) {
    return;
  }
  ASSERT(defer_oob_messages_count_ == 0);
  ASSERT(deferred_interrupts_mask_ == kMessageInterrupt);
  deferred_interrupts_mask_ = 0;
  if (deferred_interrupts_ != 0) {
    if (stack_limit_ == saved_stack_limit_) {
      stack_limit_ = kInterruptStackLimit & ~kInterruptsMask;
    }
    stack_limit_ |= deferred_interrupts_;
    deferred_interrupts_ = 0;
  }
  if (FLAG_trace_service && FLAG_trace_service_verbose) {
    OS::PrintErr("[+%" Pd64 "ms] Isolate %s restoring OOB interrupts\n",
                 Dart::UptimeMillis(), isolate()->name());
  }
}

RawError* Thread::HandleInterrupts() {
  uword interrupt_bits = GetAndClearInterrupts();
  if ((interrupt_bits & kVMInterrupt) != 0) {
    if (isolate()->store_buffer()->Overflowed()) {
      if (FLAG_verbose_gc) {
        OS::PrintErr("Scavenge scheduled by store buffer overflow.\n");
      }
      heap()->CollectGarbage(Heap::kNew);
    }
    heap()->CheckFinishConcurrentMarking(this);
  }
  if ((interrupt_bits & kMessageInterrupt) != 0) {
    MessageHandler::MessageStatus status =
        isolate()->message_handler()->HandleOOBMessages();
    if (status != MessageHandler::kOK) {
      // False result from HandleOOBMessages signals that the isolate should
      // be terminating.
      if (FLAG_trace_isolates) {
        OS::PrintErr(
            "[!] Terminating isolate due to OOB message:\n"
            "\tisolate:    %s\n",
            isolate()->name());
      }
      Thread* thread = Thread::Current();
      const Error& error = Error::Handle(thread->sticky_error());
      ASSERT(!error.IsNull() && error.IsUnwindError());
      thread->clear_sticky_error();
      return error.raw();
    }
  }
  return Error::null();
}

uword Thread::GetAndClearStackOverflowFlags() {
  uword stack_overflow_flags = stack_overflow_flags_;
  stack_overflow_flags_ = 0;
  return stack_overflow_flags;
}

void Thread::StoreBufferBlockProcess(StoreBuffer::ThresholdPolicy policy) {
  StoreBufferRelease(policy);
  StoreBufferAcquire();
}

void Thread::StoreBufferAddObject(RawObject* obj) {
  store_buffer_block_->Push(obj);
  if (store_buffer_block_->IsFull()) {
    StoreBufferBlockProcess(StoreBuffer::kCheckThreshold);
  }
}

void Thread::StoreBufferAddObjectGC(RawObject* obj) {
  store_buffer_block_->Push(obj);
  if (store_buffer_block_->IsFull()) {
    StoreBufferBlockProcess(StoreBuffer::kIgnoreThreshold);
  }
}

void Thread::StoreBufferRelease(StoreBuffer::ThresholdPolicy policy) {
  StoreBufferBlock* block = store_buffer_block_;
  store_buffer_block_ = NULL;
  isolate()->store_buffer()->PushBlock(block, policy);
}

void Thread::StoreBufferAcquire() {
  store_buffer_block_ = isolate()->store_buffer()->PopNonFullBlock();
}

void Thread::MarkingStackBlockProcess() {
  MarkingStackRelease();
  MarkingStackAcquire();
}

void Thread::MarkingStackAddObject(RawObject* obj) {
  marking_stack_block_->Push(obj);
  if (marking_stack_block_->IsFull()) {
    MarkingStackBlockProcess();
  }
}

void Thread::MarkingStackRelease() {
  MarkingStackBlock* block = marking_stack_block_;
  marking_stack_block_ = NULL;
  write_barrier_mask_ = RawObject::kGenerationalBarrierMask;
  isolate()->marking_stack()->PushBlock(block);
}

void Thread::MarkingStackAcquire() {
  marking_stack_block_ = isolate()->marking_stack()->PopEmptyBlock();
  write_barrier_mask_ =
      RawObject::kGenerationalBarrierMask | RawObject::kIncrementalBarrierMask;
}

bool Thread::IsMutatorThread() const {
  return ((isolate_ != NULL) && (isolate_->mutator_thread() == this));
}

bool Thread::CanCollectGarbage() const {
  // We grow the heap instead of triggering a garbage collection when a
  // thread is at a safepoint in the following situations :
  //   - background compiler thread finalizing and installing code
  //   - disassembly of the generated code is done after compilation
  // So essentially we state that garbage collection is possible only
  // when we are not at a safepoint.
  return !IsAtSafepoint();
}

bool Thread::IsExecutingDartCode() const {
  return (top_exit_frame_info() == 0) && VMTag::IsDartTag(vm_tag());
}

bool Thread::HasExitedDartCode() const {
  return (top_exit_frame_info() != 0) && !VMTag::IsDartTag(vm_tag());
}

template <class C>
C* Thread::AllocateReusableHandle() {
  C* handle = reinterpret_cast<C*>(reusable_handles_.AllocateScopedHandle());
  C::initializeHandle(handle, C::null());
  return handle;
}

void Thread::ClearReusableHandles() {
#define CLEAR_REUSABLE_HANDLE(object) *object##_handle_ = object::null();
  REUSABLE_HANDLE_LIST(CLEAR_REUSABLE_HANDLE)
#undef CLEAR_REUSABLE_HANDLE
}

void Thread::VisitObjectPointers(ObjectPointerVisitor* visitor,
                                 ValidationPolicy validation_policy) {
  ASSERT(visitor != NULL);

  if (zone_ != NULL) {
    zone_->VisitObjectPointers(visitor);
  }

  // Visit objects in thread specific handles area.
  reusable_handles_.VisitObjectPointers(visitor);

  visitor->VisitPointer(reinterpret_cast<RawObject**>(&pending_functions_));
  visitor->VisitPointer(reinterpret_cast<RawObject**>(&active_exception_));
  visitor->VisitPointer(reinterpret_cast<RawObject**>(&active_stacktrace_));
  visitor->VisitPointer(reinterpret_cast<RawObject**>(&sticky_error_));
  visitor->VisitPointer(reinterpret_cast<RawObject**>(&async_stack_trace_));

#if !defined(DART_PRECOMPILED_RUNTIME)
  if (interpreter() != NULL) {
    interpreter()->VisitObjectPointers(visitor);
  }
#endif

  // Visit the api local scope as it has all the api local handles.
  ApiLocalScope* scope = api_top_scope_;
  while (scope != NULL) {
    scope->local_handles()->VisitObjectPointers(visitor);
    scope = scope->previous();
  }

  // Only the mutator thread can run Dart code.
  if (IsMutatorThread()) {
    // The MarkTask, which calls this method, can run on a different thread.  We
    // therefore assume the mutator is at a safepoint and we can iterate it's
    // stack.
    // TODO(vm-team): It would be beneficial to be able to ask the mutator
    // thread whether it is in fact blocked at the moment (at a "safepoint") so
    // we can safely iterate it's stack.
    //
    // Unfortunately we cannot use `this->IsAtSafepoint()` here because that
    // will return `false` even though the mutator thread is waiting for mark
    // tasks (which iterate it's stack) to finish.
    const StackFrameIterator::CrossThreadPolicy cross_thread_policy =
        StackFrameIterator::kAllowCrossThreadIteration;

    // Iterate over all the stack frames and visit objects on the stack.
    StackFrameIterator frames_iterator(top_exit_frame_info(), validation_policy,
                                       this, cross_thread_policy);
    StackFrame* frame = frames_iterator.NextFrame();
    while (frame != NULL) {
      frame->VisitObjectPointers(visitor);
      frame = frames_iterator.NextFrame();
    }
  } else {
    // We are not on the mutator thread.
    RELEASE_ASSERT(top_exit_frame_info() == 0);
  }
}

bool Thread::CanLoadFromThread(const Object& object) {
  // In order to allow us to use assembler helper routines with non-[Code]
  // objects *before* stubs are initialized, we only loop ver the stubs if the
  // [object] is in fact a [Code] object.
  if (object.IsCode()) {
#define CHECK_OBJECT(type_name, member_name, expr, default_init_value)         \
  if (object.raw() == expr) {                                                  \
    return true;                                                               \
  }
    CACHED_VM_STUBS_LIST(CHECK_OBJECT)
#undef CHECK_OBJECT
  }

  // For non [Code] objects we check if the object equals to any of the cached
  // non-stub entries.
#define CHECK_OBJECT(type_name, member_name, expr, default_init_value)         \
  if (object.raw() == expr) {                                                  \
    return true;                                                               \
  }
  CACHED_NON_VM_STUB_LIST(CHECK_OBJECT)
#undef CHECK_OBJECT
  return false;
}

intptr_t Thread::OffsetFromThread(const Object& object) {
  // In order to allow us to use assembler helper routines with non-[Code]
  // objects *before* stubs are initialized, we only loop ver the stubs if the
  // [object] is in fact a [Code] object.
  if (object.IsCode()) {
#define COMPUTE_OFFSET(type_name, member_name, expr, default_init_value)       \
  ASSERT((expr)->IsVMHeapObject());                                            \
  if (object.raw() == expr) {                                                  \
    return Thread::member_name##offset();                                      \
  }
    CACHED_VM_STUBS_LIST(COMPUTE_OFFSET)
#undef COMPUTE_OFFSET
  }

  // For non [Code] objects we check if the object equals to any of the cached
  // non-stub entries.
#define COMPUTE_OFFSET(type_name, member_name, expr, default_init_value)       \
  ASSERT((expr)->IsVMHeapObject());                                            \
  if (object.raw() == expr) {                                                  \
    return Thread::member_name##offset();                                      \
  }
  CACHED_NON_VM_STUB_LIST(COMPUTE_OFFSET)
#undef COMPUTE_OFFSET

  UNREACHABLE();
  return -1;
}

bool Thread::ObjectAtOffset(intptr_t offset, Object* object) {
  if (Isolate::Current() == Dart::vm_isolate()) {
    // --disassemble-stubs runs before all the references through
    // thread have targets
    return false;
  }

#define COMPUTE_OFFSET(type_name, member_name, expr, default_init_value)       \
  if (Thread::member_name##offset() == offset) {                               \
    *object = expr;                                                            \
    return true;                                                               \
  }
  CACHED_VM_OBJECTS_LIST(COMPUTE_OFFSET)
#undef COMPUTE_OFFSET
  return false;
}

intptr_t Thread::OffsetFromThread(const RuntimeEntry* runtime_entry) {
#define COMPUTE_OFFSET(name)                                                   \
  if (runtime_entry->function() == k##name##RuntimeEntry.function()) {         \
    return Thread::name##_entry_point_offset();                                \
  }
  RUNTIME_ENTRY_LIST(COMPUTE_OFFSET)
#undef COMPUTE_OFFSET

#define COMPUTE_OFFSET(returntype, name, ...)                                  \
  if (runtime_entry->function() == k##name##RuntimeEntry.function()) {         \
    return Thread::name##_entry_point_offset();                                \
  }
  LEAF_RUNTIME_ENTRY_LIST(COMPUTE_OFFSET)
#undef COMPUTE_OFFSET

  UNREACHABLE();
  return -1;
}

bool Thread::IsValidHandle(Dart_Handle object) const {
  return IsValidLocalHandle(object) || IsValidZoneHandle(object) ||
         IsValidScopedHandle(object);
}

bool Thread::IsValidLocalHandle(Dart_Handle object) const {
  ApiLocalScope* scope = api_top_scope_;
  while (scope != NULL) {
    if (scope->local_handles()->IsValidHandle(object)) {
      return true;
    }
    scope = scope->previous();
  }
  return false;
}

intptr_t Thread::CountLocalHandles() const {
  intptr_t total = 0;
  ApiLocalScope* scope = api_top_scope_;
  while (scope != NULL) {
    total += scope->local_handles()->CountHandles();
    scope = scope->previous();
  }
  return total;
}

bool Thread::IsValidZoneHandle(Dart_Handle object) const {
  Zone* zone = zone_;
  while (zone != NULL) {
    if (zone->handles()->IsValidZoneHandle(reinterpret_cast<uword>(object))) {
      return true;
    }
    zone = zone->previous();
  }
  return false;
}

intptr_t Thread::CountZoneHandles() const {
  intptr_t count = 0;
  Zone* zone = zone_;
  while (zone != NULL) {
    count += zone->handles()->CountZoneHandles();
    zone = zone->previous();
  }
  ASSERT(count >= 0);
  return count;
}

bool Thread::IsValidScopedHandle(Dart_Handle object) const {
  Zone* zone = zone_;
  while (zone != NULL) {
    if (zone->handles()->IsValidScopedHandle(reinterpret_cast<uword>(object))) {
      return true;
    }
    zone = zone->previous();
  }
  return false;
}

intptr_t Thread::CountScopedHandles() const {
  intptr_t count = 0;
  Zone* zone = zone_;
  while (zone != NULL) {
    count += zone->handles()->CountScopedHandles();
    zone = zone->previous();
  }
  ASSERT(count >= 0);
  return count;
}

int Thread::ZoneSizeInBytes() const {
  int total = 0;
  ApiLocalScope* scope = api_top_scope_;
  while (scope != NULL) {
    total += scope->zone()->SizeInBytes();
    scope = scope->previous();
  }
  return total;
}

void Thread::EnterApiScope() {
  ASSERT(MayAllocateHandles());
  ApiLocalScope* new_scope = api_reusable_scope();
  if (new_scope == NULL) {
    new_scope = new ApiLocalScope(api_top_scope(), top_exit_frame_info());
    ASSERT(new_scope != NULL);
  } else {
    new_scope->Reinit(this, api_top_scope(), top_exit_frame_info());
    set_api_reusable_scope(NULL);
  }
  set_api_top_scope(new_scope);  // New scope is now the top scope.
}

void Thread::ExitApiScope() {
  ASSERT(MayAllocateHandles());
  ApiLocalScope* scope = api_top_scope();
  ApiLocalScope* reusable_scope = api_reusable_scope();
  set_api_top_scope(scope->previous());  // Reset top scope to previous.
  if (reusable_scope == NULL) {
    scope->Reset(this);  // Reset the old scope which we just exited.
    set_api_reusable_scope(scope);
  } else {
    ASSERT(reusable_scope != scope);
    delete scope;
  }
}

void Thread::UnwindScopes(uword stack_marker) {
  // Unwind all scopes using the same stack_marker, i.e. all scopes allocated
  // under the same top_exit_frame_info.
  ApiLocalScope* scope = api_top_scope_;
  while (scope != NULL && scope->stack_marker() != 0 &&
         scope->stack_marker() == stack_marker) {
    api_top_scope_ = scope->previous();
    delete scope;
    scope = api_top_scope_;
  }
}

void Thread::EnterSafepointUsingLock() {
  isolate()->safepoint_handler()->EnterSafepointUsingLock(this);
}

void Thread::ExitSafepointUsingLock() {
  isolate()->safepoint_handler()->ExitSafepointUsingLock(this);
}

void Thread::BlockForSafepoint() {
  isolate()->safepoint_handler()->BlockForSafepoint(this);
}

DisableThreadInterruptsScope::DisableThreadInterruptsScope(Thread* thread)
    : StackResource(thread) {
  if (thread != NULL) {
    OSThread* os_thread = thread->os_thread();
    ASSERT(os_thread != NULL);
    os_thread->DisableThreadInterrupts();
  }
}

DisableThreadInterruptsScope::~DisableThreadInterruptsScope() {
  if (thread() != NULL) {
    OSThread* os_thread = thread()->os_thread();
    ASSERT(os_thread != NULL);
    os_thread->EnableThreadInterrupts();
  }
}

}  // namespace dart