runtime/gc/system_weak_test.cc

/*
 * Copyright (C) 2016 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 "system_weak.h"

#include <stdint.h>
#include <stdio.h>
#include <memory>

#include "base/mutex.h"
#include "collector_type.h"
#include "common_runtime_test.h"
#include "gc_root-inl.h"
#include "handle_scope-inl.h"
#include "heap.h"
#include "mirror/object-inl.h"
#include "mirror/string.h"
#include "scoped_thread_state_change-inl.h"
#include "thread_list.h"

namespace art HIDDEN {
namespace gc {

class SystemWeakTest : public CommonRuntimeTest {
 protected:
  SystemWeakTest() {
    use_boot_image_ = true;  // Make the Runtime creation cheaper.
  }
};

struct CountingSystemWeakHolder : public SystemWeakHolder {
  CountingSystemWeakHolder()
      : SystemWeakHolder(kAllocTrackerLock),
        allow_count_(0),
        disallow_count_(0),
        sweep_count_(0) {}

  void Allow() override
      REQUIRES_SHARED(Locks::mutator_lock_)
      REQUIRES(!allow_disallow_lock_) {
    SystemWeakHolder::Allow();

    allow_count_++;
  }

  void Disallow() override
      REQUIRES_SHARED(Locks::mutator_lock_)
      REQUIRES(!allow_disallow_lock_) {
    SystemWeakHolder::Disallow();

    disallow_count_++;
  }

  void Broadcast(bool broadcast_for_checkpoint) override
      REQUIRES(!allow_disallow_lock_) {
    SystemWeakHolder::Broadcast(broadcast_for_checkpoint);

    if (!broadcast_for_checkpoint) {
      // Don't count the broadcasts for running checkpoints.
      allow_count_++;
    }
  }

  void Sweep(IsMarkedVisitor* visitor) override
      REQUIRES_SHARED(Locks::mutator_lock_)
      REQUIRES(!allow_disallow_lock_) {
    MutexLock mu(Thread::Current(), allow_disallow_lock_);
    mirror::Object* old_object = weak_.Read<kWithoutReadBarrier>();
    mirror::Object* new_object = old_object == nullptr ? nullptr : visitor->IsMarked(old_object);
    weak_ = GcRoot<mirror::Object>(new_object);

    sweep_count_++;
  }

  GcRoot<mirror::Object> Get()
      REQUIRES_SHARED(Locks::mutator_lock_)
      REQUIRES(!allow_disallow_lock_) {
    Thread* self = Thread::Current();
    MutexLock mu(self, allow_disallow_lock_);
    Wait(self);

    return weak_;
  }

  void Set(GcRoot<mirror::Object> obj)
      REQUIRES_SHARED(Locks::mutator_lock_)
      REQUIRES(!allow_disallow_lock_) {
    Thread* self = Thread::Current();
    MutexLock mu(self, allow_disallow_lock_);
    Wait(self);

    weak_ = obj;
  }

  size_t allow_count_;
  size_t disallow_count_;
  size_t sweep_count_;
  GcRoot<mirror::Object> weak_ GUARDED_BY(allow_disallow_lock_);
};

static bool CollectorDoesAllowOrBroadcast() {
  CollectorType type = Runtime::Current()->GetHeap()->CurrentCollectorType();
  switch (type) {
    case CollectorType::kCollectorTypeCMS:
    case CollectorType::kCollectorTypeCMC:
    case CollectorType::kCollectorTypeCC:
    case CollectorType::kCollectorTypeSS:
      return true;

    default:
      return false;
  }
}

static bool CollectorDoesDisallow() {
  CollectorType type = Runtime::Current()->GetHeap()->CurrentCollectorType();
  switch (type) {
    case CollectorType::kCollectorTypeCMS:
    case CollectorType::kCollectorTypeCMC:
      return true;

    default:
      return false;
  }
}

TEST_F(SystemWeakTest, Keep) {
  CountingSystemWeakHolder cswh;
  Runtime::Current()->AddSystemWeakHolder(&cswh);

  ScopedObjectAccess soa(Thread::Current());

  StackHandleScope<1> hs(soa.Self());

  // We use Strings because they are very easy to allocate.
  Handle<mirror::String> s(hs.NewHandle(mirror::String::AllocFromModifiedUtf8(soa.Self(), "ABC")));
  cswh.Set(GcRoot<mirror::Object>(s.Get()));

  // Trigger a GC.
  Runtime::Current()->GetHeap()->CollectGarbage(/* clear_soft_references= */ false);

  // Expect the holder to have been called.
  EXPECT_EQ(CollectorDoesAllowOrBroadcast() ? 1U : 0U, cswh.allow_count_);
  EXPECT_EQ(CollectorDoesDisallow() ? 1U : 0U, cswh.disallow_count_);
  // Userfaultfd GC uses SweepSystemWeaks also for concurrent updation.
  // TODO: Explore this can be reverted back to unconditionally compare with 1
  // once concurrent updation of native roots is full implemented in userfaultfd
  // GC.
  size_t expected_sweep_count = gUseUserfaultfd ? 2U : 1U;
  EXPECT_EQ(expected_sweep_count, cswh.sweep_count_);

  // Expect the weak to not be cleared.
  EXPECT_FALSE(cswh.Get().IsNull());
  EXPECT_EQ(cswh.Get().Read(), s.Get());
}

TEST_F(SystemWeakTest, Discard) {
  CountingSystemWeakHolder cswh;
  Runtime::Current()->AddSystemWeakHolder(&cswh);

  ScopedObjectAccess soa(Thread::Current());

  cswh.Set(GcRoot<mirror::Object>(mirror::String::AllocFromModifiedUtf8(soa.Self(), "ABC")));

  // Trigger a GC.
  Runtime::Current()->GetHeap()->CollectGarbage(/* clear_soft_references= */ false);

  // Expect the holder to have been called.
  EXPECT_EQ(CollectorDoesAllowOrBroadcast() ? 1U : 0U, cswh.allow_count_);
  EXPECT_EQ(CollectorDoesDisallow() ? 1U : 0U, cswh.disallow_count_);
  // Userfaultfd GC uses SweepSystemWeaks also for concurrent updation.
  // TODO: Explore this can be reverted back to unconditionally compare with 1
  // once concurrent updation of native roots is full implemented in userfaultfd
  // GC.
  size_t expected_sweep_count = gUseUserfaultfd ? 2U : 1U;
  EXPECT_EQ(expected_sweep_count, cswh.sweep_count_);

  // Expect the weak to be cleared.
  EXPECT_TRUE(cswh.Get().IsNull());
}

TEST_F(SystemWeakTest, Remove) {
  CountingSystemWeakHolder cswh;
  Runtime::Current()->AddSystemWeakHolder(&cswh);

  ScopedObjectAccess soa(Thread::Current());

  StackHandleScope<1> hs(soa.Self());

  // We use Strings because they are very easy to allocate.
  Handle<mirror::String> s(hs.NewHandle(mirror::String::AllocFromModifiedUtf8(soa.Self(), "ABC")));
  cswh.Set(GcRoot<mirror::Object>(s.Get()));

  // Trigger a GC.
  Runtime::Current()->GetHeap()->CollectGarbage(/* clear_soft_references= */ false);

  // Expect the holder to have been called.
  ASSERT_EQ(CollectorDoesAllowOrBroadcast() ? 1U : 0U, cswh.allow_count_);
  ASSERT_EQ(CollectorDoesDisallow() ? 1U : 0U, cswh.disallow_count_);
  // Userfaultfd GC uses SweepSystemWeaks also for concurrent updation.
  // TODO: Explore this can be reverted back to unconditionally compare with 1
  // once concurrent updation of native roots is full implemented in userfaultfd
  // GC.
  size_t expected_sweep_count = gUseUserfaultfd ? 2U : 1U;
  EXPECT_EQ(expected_sweep_count, cswh.sweep_count_);

  // Expect the weak to not be cleared.
  ASSERT_FALSE(cswh.Get().IsNull());
  ASSERT_EQ(cswh.Get().Read(), s.Get());

  // Remove the holder.
  Runtime::Current()->RemoveSystemWeakHolder(&cswh);

  // Trigger another GC.
  Runtime::Current()->GetHeap()->CollectGarbage(/* clear_soft_references= */ false);

  // Expectation: no change in the numbers.
  EXPECT_EQ(CollectorDoesAllowOrBroadcast() ? 1U : 0U, cswh.allow_count_);
  EXPECT_EQ(CollectorDoesDisallow() ? 1U : 0U, cswh.disallow_count_);
  EXPECT_EQ(expected_sweep_count, cswh.sweep_count_);
}

}  // namespace gc
}  // namespace art