src/heap/local-heap.cc

// Copyright 2020 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "src/heap/local-heap.h"

#include <atomic>
#include <memory>

#include "src/base/logging.h"
#include "src/base/optional.h"
#include "src/base/platform/mutex.h"
#include "src/common/globals.h"
#include "src/execution/isolate.h"
#include "src/handles/local-handles.h"
#include "src/heap/collection-barrier.h"
#include "src/heap/concurrent-allocator.h"
#include "src/heap/gc-tracer.h"
#include "src/heap/heap-inl.h"
#include "src/heap/heap-write-barrier.h"
#include "src/heap/heap.h"
#include "src/heap/local-heap-inl.h"
#include "src/heap/marking-barrier.h"
#include "src/heap/parked-scope.h"
#include "src/heap/safepoint.h"

namespace v8 {
namespace internal {

namespace {
thread_local LocalHeap* current_local_heap = nullptr;
}  // namespace

LocalHeap* LocalHeap::Current() { return current_local_heap; }

#ifdef DEBUG
void LocalHeap::VerifyCurrent() {
  LocalHeap* current = LocalHeap::Current();

  if (is_main_thread())
    DCHECK_NULL(current);
  else
    DCHECK_EQ(current, this);
}
#endif

LocalHeap::LocalHeap(Heap* heap, ThreadKind kind,
                     std::unique_ptr<PersistentHandles> persistent_handles)
    : heap_(heap),
      is_main_thread_(kind == ThreadKind::kMain),
      state_(ThreadState::Parked()),
      allocation_failed_(false),
      main_thread_parked_(false),
      prev_(nullptr),
      next_(nullptr),
      handles_(new LocalHandles),
      persistent_handles_(std::move(persistent_handles)) {
  DCHECK_IMPLIES(!is_main_thread(), heap_->deserialization_complete());
  if (!is_main_thread()) SetUp();

  heap_->safepoint()->AddLocalHeap(this, [this] {
    if (!is_main_thread()) {
      WriteBarrier::SetForThread(marking_barrier_.get());
      if (heap_->incremental_marking()->IsMarking()) {
        marking_barrier_->Activate(
            heap_->incremental_marking()->IsCompacting());
      }
    }
  });

  if (persistent_handles_) {
    persistent_handles_->Attach(this);
  }
  DCHECK_NULL(current_local_heap);
  if (!is_main_thread()) current_local_heap = this;
}

LocalHeap::~LocalHeap() {
  // Park thread since removing the local heap could block.
  EnsureParkedBeforeDestruction();

  heap_->safepoint()->RemoveLocalHeap(this, [this] {
    FreeLinearAllocationArea();

    if (!is_main_thread()) {
      marking_barrier_->Publish();
      WriteBarrier::ClearForThread(marking_barrier_.get());
    }
  });

  if (!is_main_thread()) {
    DCHECK_EQ(current_local_heap, this);
    current_local_heap = nullptr;
  }

  DCHECK(gc_epilogue_callbacks_.empty());
}

void LocalHeap::SetUpMainThreadForTesting() { SetUpMainThread(); }

void LocalHeap::SetUpMainThread() {
  DCHECK(is_main_thread());
  SetUp();
}

void LocalHeap::SetUp() {
  DCHECK_NULL(old_space_allocator_);
  old_space_allocator_ =
      std::make_unique<ConcurrentAllocator>(this, heap_->old_space());

  DCHECK_NULL(code_space_allocator_);
  code_space_allocator_ =
      std::make_unique<ConcurrentAllocator>(this, heap_->code_space());

  DCHECK_NULL(shared_old_space_allocator_);
  if (heap_->isolate()->shared_isolate()) {
    shared_old_space_allocator_ =
        std::make_unique<ConcurrentAllocator>(this, heap_->shared_old_space());
  }

  DCHECK_NULL(marking_barrier_);
  marking_barrier_ = std::make_unique<MarkingBarrier>(this);
}

void LocalHeap::EnsurePersistentHandles() {
  if (!persistent_handles_) {
    persistent_handles_.reset(
        heap_->isolate()->NewPersistentHandles().release());
    persistent_handles_->Attach(this);
  }
}

void LocalHeap::AttachPersistentHandles(
    std::unique_ptr<PersistentHandles> persistent_handles) {
  DCHECK_NULL(persistent_handles_);
  persistent_handles_ = std::move(persistent_handles);
  persistent_handles_->Attach(this);
}

std::unique_ptr<PersistentHandles> LocalHeap::DetachPersistentHandles() {
  if (persistent_handles_) persistent_handles_->Detach();
  return std::move(persistent_handles_);
}

#ifdef DEBUG
bool LocalHeap::ContainsPersistentHandle(Address* location) {
  return persistent_handles_ ? persistent_handles_->Contains(location) : false;
}

bool LocalHeap::ContainsLocalHandle(Address* location) {
  return handles_ ? handles_->Contains(location) : false;
}

bool LocalHeap::IsHandleDereferenceAllowed() {
#ifdef DEBUG
  VerifyCurrent();
#endif
  return IsRunning();
}
#endif

bool LocalHeap::IsParked() {
#ifdef DEBUG
  VerifyCurrent();
#endif
  return state_.load_relaxed().IsParked();
}

bool LocalHeap::IsRunning() {
#ifdef DEBUG
  VerifyCurrent();
#endif
  return state_.load_relaxed().IsRunning();
}

void LocalHeap::ParkSlowPath() {
  while (true) {
    ThreadState current_state = ThreadState::Running();
    if (state_.CompareExchangeStrong(current_state, ThreadState::Parked()))
      return;

    // CAS above failed, so state is Running with some additional flag.
    DCHECK(current_state.IsRunning());

    if (is_main_thread()) {
      DCHECK(current_state.IsSafepointRequested() ||
             current_state.IsCollectionRequested());

      if (current_state.IsSafepointRequested()) {
        ThreadState old_state = state_.SetParked();
        heap_->safepoint()->NotifyPark();
        if (old_state.IsCollectionRequested())
          heap_->collection_barrier_->CancelCollectionAndResumeThreads();
        return;
      }

      if (current_state.IsCollectionRequested()) {
        if (!heap()->ignore_local_gc_requests()) {
          heap_->CollectGarbageForBackground(this);
          continue;
        }

        DCHECK(!current_state.IsSafepointRequested());

        if (state_.CompareExchangeStrong(current_state,
                                         current_state.SetParked())) {
          heap_->collection_barrier_->CancelCollectionAndResumeThreads();
          return;
        } else {
          continue;
        }
      }
    } else {
      DCHECK(current_state.IsSafepointRequested());
      DCHECK(!current_state.IsCollectionRequested());

      ThreadState old_state = state_.SetParked();
      CHECK(old_state.IsRunning());
      CHECK(old_state.IsSafepointRequested());
      CHECK(!old_state.IsCollectionRequested());

      heap_->safepoint()->NotifyPark();
      return;
    }
  }
}

void LocalHeap::UnparkSlowPath() {
  while (true) {
    ThreadState current_state = ThreadState::Parked();
    if (state_.CompareExchangeStrong(current_state, ThreadState::Running()))
      return;

    // CAS above failed, so state is Parked with some additional flag.
    DCHECK(current_state.IsParked());

    if (is_main_thread()) {
      DCHECK(current_state.IsSafepointRequested() ||
             current_state.IsCollectionRequested());

      if (current_state.IsSafepointRequested()) {
        SleepInUnpark();
        continue;
      }

      if (current_state.IsCollectionRequested()) {
        DCHECK(!current_state.IsSafepointRequested());

        if (!state_.CompareExchangeStrong(current_state,
                                          current_state.SetRunning()))
          continue;

        if (!heap()->ignore_local_gc_requests()) {
          heap_->CollectGarbageForBackground(this);
        }

        return;
      }
    } else {
      DCHECK(current_state.IsSafepointRequested());
      DCHECK(!current_state.IsCollectionRequested());

      SleepInUnpark();
    }
  }
}

void LocalHeap::SleepInUnpark() {
  GCTracer::Scope::ScopeId scope_id;
  ThreadKind thread_kind;

  if (is_main_thread()) {
    scope_id = GCTracer::Scope::UNPARK;
    thread_kind = ThreadKind::kMain;
  } else {
    scope_id = GCTracer::Scope::BACKGROUND_UNPARK;
    thread_kind = ThreadKind::kBackground;
  }

  TRACE_GC1(heap_->tracer(), scope_id, thread_kind);
  heap_->safepoint()->WaitInUnpark();
}

void LocalHeap::EnsureParkedBeforeDestruction() {
  DCHECK_IMPLIES(!is_main_thread(), IsParked());
}

void LocalHeap::SafepointSlowPath() {
  ThreadState current_state = state_.load_relaxed();
  DCHECK(current_state.IsRunning());

  if (is_main_thread()) {
    DCHECK(current_state.IsSafepointRequested() ||
           current_state.IsCollectionRequested());

    if (current_state.IsSafepointRequested()) {
      SleepInSafepoint();
    }

    if (current_state.IsCollectionRequested()) {
      heap_->CollectGarbageForBackground(this);
    }
  } else {
    DCHECK(current_state.IsSafepointRequested());
    DCHECK(!current_state.IsCollectionRequested());

    SleepInSafepoint();
  }
}

void LocalHeap::SleepInSafepoint() {
  GCTracer::Scope::ScopeId scope_id;
  ThreadKind thread_kind;

  if (is_main_thread()) {
    scope_id = GCTracer::Scope::SAFEPOINT;
    thread_kind = ThreadKind::kMain;
  } else {
    scope_id = GCTracer::Scope::BACKGROUND_SAFEPOINT;
    thread_kind = ThreadKind::kBackground;
  }

  TRACE_GC1(heap_->tracer(), scope_id, thread_kind);

  // Parking the running thread here is an optimization. We do not need to
  // wake this thread up to reach the next safepoint.
  ThreadState old_state = state_.SetParked();
  CHECK(old_state.IsRunning());
  CHECK(old_state.IsSafepointRequested());
  CHECK_IMPLIES(old_state.IsCollectionRequested(), is_main_thread());

  heap_->safepoint()->WaitInSafepoint();

  base::Optional<IgnoreLocalGCRequests> ignore_gc_requests;
  if (is_main_thread()) ignore_gc_requests.emplace(heap());
  Unpark();
}

void LocalHeap::FreeLinearAllocationArea() {
  old_space_allocator_->FreeLinearAllocationArea();
  code_space_allocator_->FreeLinearAllocationArea();
}

void LocalHeap::FreeSharedLinearAllocationArea() {
  shared_old_space_allocator_->FreeLinearAllocationArea();
}

void LocalHeap::MakeLinearAllocationAreaIterable() {
  old_space_allocator_->MakeLinearAllocationAreaIterable();
  code_space_allocator_->MakeLinearAllocationAreaIterable();
}

void LocalHeap::MarkLinearAllocationAreaBlack() {
  old_space_allocator_->MarkLinearAllocationAreaBlack();
  code_space_allocator_->MarkLinearAllocationAreaBlack();
}

void LocalHeap::UnmarkLinearAllocationArea() {
  old_space_allocator_->UnmarkLinearAllocationArea();
  code_space_allocator_->UnmarkLinearAllocationArea();
}

bool LocalHeap::TryPerformCollection() {
  if (is_main_thread()) {
    heap_->CollectGarbageForBackground(this);
    return true;
  } else {
    DCHECK(IsRunning());
    if (!heap_->collection_barrier_->TryRequestGC()) return false;

    LocalHeap* main_thread = heap_->main_thread_local_heap();

    const ThreadState old_state = main_thread->state_.SetCollectionRequested();

    if (old_state.IsRunning()) {
      const bool performed_gc =
          heap_->collection_barrier_->AwaitCollectionBackground(this);
      return performed_gc;
    } else {
      DCHECK(old_state.IsParked());
      return false;
    }
  }
}

Address LocalHeap::PerformCollectionAndAllocateAgain(
    int object_size, AllocationType type, AllocationOrigin origin,
    AllocationAlignment alignment) {
  CHECK(!allocation_failed_);
  CHECK(!main_thread_parked_);
  allocation_failed_ = true;
  static const int kMaxNumberOfRetries = 3;

  for (int i = 0; i < kMaxNumberOfRetries; i++) {
    if (!TryPerformCollection()) {
      main_thread_parked_ = true;
    }

    AllocationResult result = AllocateRaw(object_size, type, origin, alignment);

    if (!result.IsFailure()) {
      allocation_failed_ = false;
      main_thread_parked_ = false;
      return result.ToObjectChecked().address();
    }
  }

  heap_->FatalProcessOutOfMemory("LocalHeap: allocation failed");
}

void LocalHeap::AddGCEpilogueCallback(GCEpilogueCallback* callback,
                                      void* data) {
  DCHECK(!IsParked());
  std::pair<GCEpilogueCallback*, void*> callback_and_data(callback, data);
  DCHECK_EQ(std::find(gc_epilogue_callbacks_.begin(),
                      gc_epilogue_callbacks_.end(), callback_and_data),
            gc_epilogue_callbacks_.end());
  gc_epilogue_callbacks_.push_back(callback_and_data);
}

void LocalHeap::RemoveGCEpilogueCallback(GCEpilogueCallback* callback,
                                         void* data) {
  DCHECK(!IsParked());
  std::pair<GCEpilogueCallback*, void*> callback_and_data(callback, data);
  auto it = std::find(gc_epilogue_callbacks_.begin(),
                      gc_epilogue_callbacks_.end(), callback_and_data);
  *it = gc_epilogue_callbacks_.back();
  gc_epilogue_callbacks_.pop_back();
}

void LocalHeap::InvokeGCEpilogueCallbacksInSafepoint() {
  for (auto callback_and_data : gc_epilogue_callbacks_) {
    callback_and_data.first(callback_and_data.second);
  }
}

}  // namespace internal
}  // namespace v8