runtime/monitor_test.cc - platform/art - Gitiles

 /*
  * Copyright (C) 2014 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 "barrier.h"
 #include "monitor.h"

 #include <string>

 #include "atomic.h"
 #include "base/time_utils.h"
 #include "class_linker-inl.h"
 #include "common_runtime_test.h"
 #include "handle_scope-inl.h"
 #include "mirror/class-inl.h"
 #include "mirror/string-inl.h"  // Strings are easiest to allocate
 #include "object_lock.h"
 #include "scoped_thread_state_change-inl.h"
 #include "thread_pool.h"

 namespace art {

 class MonitorTest : public CommonRuntimeTest {
  protected:
   void SetUpRuntimeOptions(RuntimeOptions *options) OVERRIDE {
     // Use a smaller heap
     for (std::pair<std::string, const void*>& pair : *options) {
       if (pair.first.find("-Xmx") == 0) {
         pair.first = "-Xmx4M";  // Smallest we can go.
       }
     }
     options->push_back(std::make_pair("-Xint", nullptr));
   }
  public:
   std::unique_ptr<Monitor> monitor_;
   Handle<mirror::String> object_;
   Handle<mirror::String> second_object_;
   Handle<mirror::String> watchdog_object_;
   // One exception test is for waiting on another Thread's lock. This is used to race-free &
   // loop-free pass
   Thread* thread_;
   std::unique_ptr<Barrier> barrier_;
   std::unique_ptr<Barrier> complete_barrier_;
   bool completed_;
 };

 // Fill the heap.
 static const size_t kMaxHandles = 1000000;  // Use arbitrary large amount for now.
 static void FillHeap(Thread* self, ClassLinker* class_linker,
                      std::unique_ptr<StackHandleScope<kMaxHandles>>* hsp,
                      std::vector<MutableHandle<mirror::Object>>* handles)
     REQUIRES_SHARED(Locks::mutator_lock_) {
   Runtime::Current()->GetHeap()->SetIdealFootprint(1 * GB);

   hsp->reset(new StackHandleScope<kMaxHandles>(self));
   // Class java.lang.Object.
   Handle<mirror::Class> c((*hsp)->NewHandle(class_linker->FindSystemClass(self,
                                                                        "Ljava/lang/Object;")));
   // Array helps to fill memory faster.
   Handle<mirror::Class> ca((*hsp)->NewHandle(class_linker->FindSystemClass(self,
                                                                         "[Ljava/lang/Object;")));

   // Start allocating with 128K
   size_t length = 128 * KB / 4;
   while (length > 10) {
     MutableHandle<mirror::Object> h((*hsp)->NewHandle<mirror::Object>(
         mirror::ObjectArray<mirror::Object>::Alloc(self, ca.Get(), length / 4)));
     if (self->IsExceptionPending() || h.Get() == nullptr) {
       self->ClearException();

       // Try a smaller length
       length = length / 8;
       // Use at most half the reported free space.
       size_t mem = Runtime::Current()->GetHeap()->GetFreeMemory();
       if (length * 8 > mem) {
         length = mem / 8;
       }
     } else {
       handles->push_back(h);
     }
   }

   // Allocate simple objects till it fails.
   while (!self->IsExceptionPending()) {
     MutableHandle<mirror::Object> h = (*hsp)->NewHandle<mirror::Object>(c->AllocObject(self));
     if (!self->IsExceptionPending() && h.Get() != nullptr) {
       handles->push_back(h);
     }
   }
   self->ClearException();
 }

 // Check that an exception can be thrown correctly.
 // This test is potentially racy, but the timeout is long enough that it should work.

 class CreateTask : public Task {
  public:
   CreateTask(MonitorTest* monitor_test, uint64_t initial_sleep, int64_t millis, bool expected) :
       monitor_test_(monitor_test), initial_sleep_(initial_sleep), millis_(millis),
       expected_(expected) {}

   void Run(Thread* self) {
     {
       ScopedObjectAccess soa(self);

       monitor_test_->thread_ = self;        // Pass the Thread.
       monitor_test_->object_.Get()->MonitorEnter(self);  // Lock the object. This should transition
       LockWord lock_after = monitor_test_->object_.Get()->GetLockWord(false);  // it to thinLocked.
       LockWord::LockState new_state = lock_after.GetState();

       // Cannot use ASSERT only, as analysis thinks we'll keep holding the mutex.
       if (LockWord::LockState::kThinLocked != new_state) {
         monitor_test_->object_.Get()->MonitorExit(self);         // To appease analysis.
         ASSERT_EQ(LockWord::LockState::kThinLocked, new_state);  // To fail the test.
         return;
       }

       // Force a fat lock by running identity hashcode to fill up lock word.
       monitor_test_->object_.Get()->IdentityHashCode();
       LockWord lock_after2 = monitor_test_->object_.Get()->GetLockWord(false);
       LockWord::LockState new_state2 = lock_after2.GetState();

       // Cannot use ASSERT only, as analysis thinks we'll keep holding the mutex.
       if (LockWord::LockState::kFatLocked != new_state2) {
         monitor_test_->object_.Get()->MonitorExit(self);         // To appease analysis.
         ASSERT_EQ(LockWord::LockState::kFatLocked, new_state2);  // To fail the test.
         return;
       }
     }  // Need to drop the mutator lock to use the barrier.

     monitor_test_->barrier_->Wait(self);           // Let the other thread know we're done.

     {
       ScopedObjectAccess soa(self);

       // Give the other task a chance to do its thing.
       NanoSleep(initial_sleep_ * 1000 * 1000);

       // Now try to Wait on the Monitor.
       Monitor::Wait(self, monitor_test_->object_.Get(), millis_, 0, true,
                     ThreadState::kTimedWaiting);

       // Check the exception status against what we expect.
       EXPECT_EQ(expected_, self->IsExceptionPending());
       if (expected_) {
         self->ClearException();
       }
     }

     monitor_test_->complete_barrier_->Wait(self);  // Wait for test completion.

     {
       ScopedObjectAccess soa(self);
       monitor_test_->object_.Get()->MonitorExit(self);  // Release the object. Appeases analysis.
     }
   }

   void Finalize() {
     delete this;
   }

  private:
   MonitorTest* monitor_test_;
   uint64_t initial_sleep_;
   int64_t millis_;
   bool expected_;
 };


 class UseTask : public Task {
  public:
   UseTask(MonitorTest* monitor_test, uint64_t initial_sleep, int64_t millis, bool expected) :
       monitor_test_(monitor_test), initial_sleep_(initial_sleep), millis_(millis),
       expected_(expected) {}

   void Run(Thread* self) {
     monitor_test_->barrier_->Wait(self);  // Wait for the other thread to set up the monitor.

     {
       ScopedObjectAccess soa(self);

       // Give the other task a chance to do its thing.
       NanoSleep(initial_sleep_ * 1000 * 1000);

       Monitor::Wait(self, monitor_test_->object_.Get(), millis_, 0, true,
                     ThreadState::kTimedWaiting);

       // Check the exception status against what we expect.
       EXPECT_EQ(expected_, self->IsExceptionPending());
       if (expected_) {
         self->ClearException();
       }
     }

     monitor_test_->complete_barrier_->Wait(self);  // Wait for test completion.
   }

   void Finalize() {
     delete this;
   }

  private:
   MonitorTest* monitor_test_;
   uint64_t initial_sleep_;
   int64_t millis_;
   bool expected_;
 };

 class InterruptTask : public Task {
  public:
   InterruptTask(MonitorTest* monitor_test, uint64_t initial_sleep, uint64_t millis) :
       monitor_test_(monitor_test), initial_sleep_(initial_sleep), millis_(millis) {}

   void Run(Thread* self) {
     monitor_test_->barrier_->Wait(self);  // Wait for the other thread to set up the monitor.

     {
       ScopedObjectAccess soa(self);

       // Give the other task a chance to do its thing.
       NanoSleep(initial_sleep_ * 1000 * 1000);

       // Interrupt the other thread.
       monitor_test_->thread_->Interrupt(self);

       // Give it some more time to get to the exception code.
       NanoSleep(millis_ * 1000 * 1000);

       // Now try to Wait.
       Monitor::Wait(self, monitor_test_->object_.Get(), 10, 0, true,
                     ThreadState::kTimedWaiting);

       // No check here, as depending on scheduling we may or may not fail.
       if (self->IsExceptionPending()) {
         self->ClearException();
       }
     }

     monitor_test_->complete_barrier_->Wait(self);  // Wait for test completion.
   }

   void Finalize() {
     delete this;
   }

  private:
   MonitorTest* monitor_test_;
   uint64_t initial_sleep_;
   uint64_t millis_;
 };

 class WatchdogTask : public Task {
  public:
   explicit WatchdogTask(MonitorTest* monitor_test) : monitor_test_(monitor_test) {}

   void Run(Thread* self) {
     ScopedObjectAccess soa(self);

     monitor_test_->watchdog_object_.Get()->MonitorEnter(self);        // Lock the object.

     monitor_test_->watchdog_object_.Get()->Wait(self, 30 * 1000, 0);  // Wait for 30s, or being
                                                                       // woken up.

     monitor_test_->watchdog_object_.Get()->MonitorExit(self);         // Release the lock.

     if (!monitor_test_->completed_) {
       LOG(FATAL) << "Watchdog timeout!";
     }
   }

   void Finalize() {
     delete this;
   }

  private:
   MonitorTest* monitor_test_;
 };

 static void CommonWaitSetup(MonitorTest* test, ClassLinker* class_linker, uint64_t create_sleep,
                             int64_t c_millis, bool c_expected, bool interrupt, uint64_t use_sleep,
                             int64_t u_millis, bool u_expected, const char* pool_name) {
   Thread* const self = Thread::Current();
   ScopedObjectAccess soa(self);
   // First create the object we lock. String is easiest.
   StackHandleScope<3> hs(soa.Self());
   test->object_ = hs.NewHandle(mirror::String::AllocFromModifiedUtf8(self, "hello, world!"));
   test->watchdog_object_ = hs.NewHandle(mirror::String::AllocFromModifiedUtf8(self,
                                                                               "hello, world!"));

   // Create the barrier used to synchronize.
   test->barrier_ = std::unique_ptr<Barrier>(new Barrier(2));
   test->complete_barrier_ = std::unique_ptr<Barrier>(new Barrier(3));
   test->completed_ = false;

   // Fill the heap.
   std::unique_ptr<StackHandleScope<kMaxHandles>> hsp;
   std::vector<MutableHandle<mirror::Object>> handles;

   // Our job: Fill the heap, then try Wait.
   FillHeap(soa.Self(), class_linker, &hsp, &handles);

   // Now release everything.
   for (MutableHandle<mirror::Object>& h : handles) {
     h.Assign(nullptr);
   }

   // Need to drop the mutator lock to allow barriers.
   ScopedThreadSuspension sts(soa.Self(), kNative);
   ThreadPool thread_pool(pool_name, 3);
   thread_pool.AddTask(self, new CreateTask(test, create_sleep, c_millis, c_expected));
   if (interrupt) {
     thread_pool.AddTask(self, new InterruptTask(test, use_sleep, static_cast<uint64_t>(u_millis)));
   } else {
     thread_pool.AddTask(self, new UseTask(test, use_sleep, u_millis, u_expected));
   }
   thread_pool.AddTask(self, new WatchdogTask(test));
   thread_pool.StartWorkers(self);

   // Wait on completion barrier.
   test->complete_barrier_->Wait(self);
   test->completed_ = true;

   // Wake the watchdog.
   {
     ScopedObjectAccess soa2(self);
     test->watchdog_object_.Get()->MonitorEnter(self);     // Lock the object.
     test->watchdog_object_.Get()->NotifyAll(self);        // Wake up waiting parties.
     test->watchdog_object_.Get()->MonitorExit(self);      // Release the lock.
   }

   thread_pool.StopWorkers(self);
 }


 // First test: throwing an exception when trying to wait in Monitor with another thread.
 TEST_F(MonitorTest, CheckExceptionsWait1) {
   // Make the CreateTask wait 10ms, the UseTask wait 10ms.
   // => The use task will get the lock first and get to self == owner check.
   // This will lead to OOM and monitor error messages in the log.
   ScopedLogSeverity sls(LogSeverity::FATAL);
   CommonWaitSetup(this, class_linker_, 10, 50, false, false, 2, 50, true,
                   "Monitor test thread pool 1");
 }

 // Second test: throwing an exception for invalid wait time.
 TEST_F(MonitorTest, CheckExceptionsWait2) {
   // Make the CreateTask wait 0ms, the UseTask wait 10ms.
   // => The create task will get the lock first and get to ms >= 0
   // This will lead to OOM and monitor error messages in the log.
   ScopedLogSeverity sls(LogSeverity::FATAL);
   CommonWaitSetup(this, class_linker_, 0, -1, true, false, 10, 50, true,
                   "Monitor test thread pool 2");
 }

 // Third test: throwing an interrupted-exception.
 TEST_F(MonitorTest, CheckExceptionsWait3) {
   // Make the CreateTask wait 0ms, then Wait for a long time. Make the InterruptTask wait 10ms,
   // after which it will interrupt the create task and then wait another 10ms.
   // => The create task will get to the interrupted-exception throw.
   // This will lead to OOM and monitor error messages in the log.
   ScopedLogSeverity sls(LogSeverity::FATAL);
   CommonWaitSetup(this, class_linker_, 0, 500, true, true, 10, 50, true,
                   "Monitor test thread pool 3");
 }

 class TryLockTask : public Task {
  public:
   explicit TryLockTask(Handle<mirror::Object> obj) : obj_(obj) {}

   void Run(Thread* self) {
     ScopedObjectAccess soa(self);
     // Lock is held by other thread, try lock should fail.
     ObjectTryLock<mirror::Object> lock(self, obj_);
     EXPECT_FALSE(lock.Acquired());
   }

   void Finalize() {
     delete this;
   }

  private:
   Handle<mirror::Object> obj_;
 };

 // Test trylock in deadlock scenarios.
 TEST_F(MonitorTest, TestTryLock) {
   ScopedLogSeverity sls(LogSeverity::FATAL);

   Thread* const self = Thread::Current();
   ThreadPool thread_pool("the pool", 2);
   ScopedObjectAccess soa(self);
   StackHandleScope<1> hs(self);
   Handle<mirror::Object> obj1(
       hs.NewHandle<mirror::Object>(mirror::String::AllocFromModifiedUtf8(self, "hello, world!")));
   {
     ObjectLock<mirror::Object> lock1(self, obj1);
     {
       ObjectTryLock<mirror::Object> trylock(self, obj1);
       EXPECT_TRUE(trylock.Acquired());
     }
     // Test failure case.
     thread_pool.AddTask(self, new TryLockTask(obj1));
     thread_pool.StartWorkers(self);
     ScopedThreadSuspension sts(self, kSuspended);
     thread_pool.Wait(Thread::Current(), /*do_work*/false, /*may_hold_locks*/false);
   }
   // Test that the trylock actually locks the object.
   {
     ObjectTryLock<mirror::Object> trylock(self, obj1);
     EXPECT_TRUE(trylock.Acquired());
     obj1->Notify(self);
     // Since we hold the lock there should be no monitor state exeception.
     self->AssertNoPendingException();
   }
   thread_pool.StopWorkers(self);
 }


 }  // namespace art
	/*
	* Copyright (C) 2014 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 "barrier.h"
	#include "monitor.h"

	#include <string>

	#include "atomic.h"
	#include "base/time_utils.h"
	#include "class_linker-inl.h"
	#include "common_runtime_test.h"
	#include "handle_scope-inl.h"
	#include "mirror/class-inl.h"
	#include "mirror/string-inl.h" // Strings are easiest to allocate
	#include "object_lock.h"
	#include "scoped_thread_state_change-inl.h"
	#include "thread_pool.h"

	namespace art {

	class MonitorTest : public CommonRuntimeTest {
	protected:
	void SetUpRuntimeOptions(RuntimeOptions *options) OVERRIDE {
	// Use a smaller heap
	for (std::pair<std::string, const void>& pair : options) {
	if (pair.first.find("-Xmx") == 0) {
	pair.first = "-Xmx4M"; // Smallest we can go.
	}
	}
	options->push_back(std::make_pair("-Xint", nullptr));
	}
	public:
	std::unique_ptr<Monitor> monitor_;
	Handle<mirror::String> object_;
	Handle<mirror::String> second_object_;
	Handle<mirror::String> watchdog_object_;
	// One exception test is for waiting on another Thread's lock. This is used to race-free &
	// loop-free pass
	Thread* thread_;
	std::unique_ptr<Barrier> barrier_;
	std::unique_ptr<Barrier> complete_barrier_;
	bool completed_;
	};

	// Fill the heap.
	static const size_t kMaxHandles = 1000000; // Use arbitrary large amount for now.
	static void FillHeap(Thread* self, ClassLinker* class_linker,
	std::unique_ptr<StackHandleScope<kMaxHandles>>* hsp,
	std::vector<MutableHandle<mirror::Object>>* handles)
	REQUIRES_SHARED(Locks::mutator_lock_) {
	Runtime::Current()->GetHeap()->SetIdealFootprint(1 * GB);

	hsp->reset(new StackHandleScope<kMaxHandles>(self));
	// Class java.lang.Object.
	Handle<mirror::Class> c((*hsp)->NewHandle(class_linker->FindSystemClass(self,
	"Ljava/lang/Object;")));
	// Array helps to fill memory faster.
	Handle<mirror::Class> ca((*hsp)->NewHandle(class_linker->FindSystemClass(self,
	"[Ljava/lang/Object;")));

	// Start allocating with 128K
	size_t length = 128 * KB / 4;
	while (length > 10) {
	MutableHandle<mirror::Object> h((*hsp)->NewHandle<mirror::Object>(
	mirror::ObjectArray<mirror::Object>::Alloc(self, ca.Get(), length / 4)));
	if (self->IsExceptionPending() \|\| h.Get() == nullptr) {
	self->ClearException();

	// Try a smaller length
	length = length / 8;
	// Use at most half the reported free space.
	size_t mem = Runtime::Current()->GetHeap()->GetFreeMemory();
	if (length * 8 > mem) {
	length = mem / 8;
	}
	} else {
	handles->push_back(h);
	}
	}

	// Allocate simple objects till it fails.
	while (!self->IsExceptionPending()) {
	MutableHandle<mirror::Object> h = (*hsp)->NewHandle<mirror::Object>(c->AllocObject(self));
	if (!self->IsExceptionPending() && h.Get() != nullptr) {
	handles->push_back(h);
	}
	}
	self->ClearException();
	}

	// Check that an exception can be thrown correctly.
	// This test is potentially racy, but the timeout is long enough that it should work.

	class CreateTask : public Task {
	public:
	CreateTask(MonitorTest* monitor_test, uint64_t initial_sleep, int64_t millis, bool expected) :
	monitor_test_(monitor_test), initial_sleep_(initial_sleep), millis_(millis),
	expected_(expected) {}

	void Run(Thread* self) {
	{
	ScopedObjectAccess soa(self);

	monitor_test_->thread_ = self; // Pass the Thread.
	monitor_test_->object_.Get()->MonitorEnter(self); // Lock the object. This should transition
	LockWord lock_after = monitor_test_->object_.Get()->GetLockWord(false); // it to thinLocked.
	LockWord::LockState new_state = lock_after.GetState();

	// Cannot use ASSERT only, as analysis thinks we'll keep holding the mutex.
	if (LockWord::LockState::kThinLocked != new_state) {
	monitor_test_->object_.Get()->MonitorExit(self); // To appease analysis.
	ASSERT_EQ(LockWord::LockState::kThinLocked, new_state); // To fail the test.
	return;
	}

	// Force a fat lock by running identity hashcode to fill up lock word.
	monitor_test_->object_.Get()->IdentityHashCode();
	LockWord lock_after2 = monitor_test_->object_.Get()->GetLockWord(false);
	LockWord::LockState new_state2 = lock_after2.GetState();

	// Cannot use ASSERT only, as analysis thinks we'll keep holding the mutex.
	if (LockWord::LockState::kFatLocked != new_state2) {
	monitor_test_->object_.Get()->MonitorExit(self); // To appease analysis.
	ASSERT_EQ(LockWord::LockState::kFatLocked, new_state2); // To fail the test.
	return;
	}
	} // Need to drop the mutator lock to use the barrier.

	monitor_test_->barrier_->Wait(self); // Let the other thread know we're done.

	{
	ScopedObjectAccess soa(self);

	// Give the other task a chance to do its thing.
	NanoSleep(initial_sleep_ * 1000 * 1000);

	// Now try to Wait on the Monitor.
	Monitor::Wait(self, monitor_test_->object_.Get(), millis_, 0, true,
	ThreadState::kTimedWaiting);

	// Check the exception status against what we expect.
	EXPECT_EQ(expected_, self->IsExceptionPending());
	if (expected_) {
	self->ClearException();
	}
	}

	monitor_test_->complete_barrier_->Wait(self); // Wait for test completion.

	{
	ScopedObjectAccess soa(self);
	monitor_test_->object_.Get()->MonitorExit(self); // Release the object. Appeases analysis.
	}
	}

	void Finalize() {
	delete this;
	}

	private:
	MonitorTest* monitor_test_;
	uint64_t initial_sleep_;
	int64_t millis_;
	bool expected_;
	};


	class UseTask : public Task {
	public:
	UseTask(MonitorTest* monitor_test, uint64_t initial_sleep, int64_t millis, bool expected) :
	monitor_test_(monitor_test), initial_sleep_(initial_sleep), millis_(millis),
	expected_(expected) {}

	void Run(Thread* self) {
	monitor_test_->barrier_->Wait(self); // Wait for the other thread to set up the monitor.

	{
	ScopedObjectAccess soa(self);

	// Give the other task a chance to do its thing.
	NanoSleep(initial_sleep_ * 1000 * 1000);

	Monitor::Wait(self, monitor_test_->object_.Get(), millis_, 0, true,
	ThreadState::kTimedWaiting);

	// Check the exception status against what we expect.
	EXPECT_EQ(expected_, self->IsExceptionPending());
	if (expected_) {
	self->ClearException();
	}
	}

	monitor_test_->complete_barrier_->Wait(self); // Wait for test completion.
	}

	void Finalize() {
	delete this;
	}

	private:
	MonitorTest* monitor_test_;
	uint64_t initial_sleep_;
	int64_t millis_;
	bool expected_;
	};

	class InterruptTask : public Task {
	public:
	InterruptTask(MonitorTest* monitor_test, uint64_t initial_sleep, uint64_t millis) :
	monitor_test_(monitor_test), initial_sleep_(initial_sleep), millis_(millis) {}

	void Run(Thread* self) {
	monitor_test_->barrier_->Wait(self); // Wait for the other thread to set up the monitor.

	{
	ScopedObjectAccess soa(self);

	// Give the other task a chance to do its thing.
	NanoSleep(initial_sleep_ * 1000 * 1000);

	// Interrupt the other thread.
	monitor_test_->thread_->Interrupt(self);

	// Give it some more time to get to the exception code.
	NanoSleep(millis_ * 1000 * 1000);

	// Now try to Wait.
	Monitor::Wait(self, monitor_test_->object_.Get(), 10, 0, true,
	ThreadState::kTimedWaiting);

	// No check here, as depending on scheduling we may or may not fail.
	if (self->IsExceptionPending()) {
	self->ClearException();
	}
	}

	monitor_test_->complete_barrier_->Wait(self); // Wait for test completion.
	}

	void Finalize() {
	delete this;
	}

	private:
	MonitorTest* monitor_test_;
	uint64_t initial_sleep_;
	uint64_t millis_;
	};

	class WatchdogTask : public Task {
	public:
	explicit WatchdogTask(MonitorTest* monitor_test) : monitor_test_(monitor_test) {}

	void Run(Thread* self) {
	ScopedObjectAccess soa(self);

	monitor_test_->watchdog_object_.Get()->MonitorEnter(self); // Lock the object.

	monitor_test_->watchdog_object_.Get()->Wait(self, 30 * 1000, 0); // Wait for 30s, or being
	// woken up.

	monitor_test_->watchdog_object_.Get()->MonitorExit(self); // Release the lock.

	if (!monitor_test_->completed_) {
	LOG(FATAL) << "Watchdog timeout!";
	}
	}

	void Finalize() {
	delete this;
	}

	private:
	MonitorTest* monitor_test_;
	};

	static void CommonWaitSetup(MonitorTest* test, ClassLinker* class_linker, uint64_t create_sleep,
	int64_t c_millis, bool c_expected, bool interrupt, uint64_t use_sleep,
	int64_t u_millis, bool u_expected, const char* pool_name) {
	Thread* const self = Thread::Current();
	ScopedObjectAccess soa(self);
	// First create the object we lock. String is easiest.
	StackHandleScope<3> hs(soa.Self());
	test->object_ = hs.NewHandle(mirror::String::AllocFromModifiedUtf8(self, "hello, world!"));
	test->watchdog_object_ = hs.NewHandle(mirror::String::AllocFromModifiedUtf8(self,
	"hello, world!"));

	// Create the barrier used to synchronize.
	test->barrier_ = std::unique_ptr<Barrier>(new Barrier(2));
	test->complete_barrier_ = std::unique_ptr<Barrier>(new Barrier(3));
	test->completed_ = false;

	// Fill the heap.
	std::unique_ptr<StackHandleScope<kMaxHandles>> hsp;
	std::vector<MutableHandle<mirror::Object>> handles;

	// Our job: Fill the heap, then try Wait.
	FillHeap(soa.Self(), class_linker, &hsp, &handles);

	// Now release everything.
	for (MutableHandle<mirror::Object>& h : handles) {
	h.Assign(nullptr);
	}

	// Need to drop the mutator lock to allow barriers.
	ScopedThreadSuspension sts(soa.Self(), kNative);
	ThreadPool thread_pool(pool_name, 3);
	thread_pool.AddTask(self, new CreateTask(test, create_sleep, c_millis, c_expected));
	if (interrupt) {
	thread_pool.AddTask(self, new InterruptTask(test, use_sleep, static_cast<uint64_t>(u_millis)));
	} else {
	thread_pool.AddTask(self, new UseTask(test, use_sleep, u_millis, u_expected));
	}
	thread_pool.AddTask(self, new WatchdogTask(test));
	thread_pool.StartWorkers(self);

	// Wait on completion barrier.
	test->complete_barrier_->Wait(self);
	test->completed_ = true;

	// Wake the watchdog.
	{
	ScopedObjectAccess soa2(self);
	test->watchdog_object_.Get()->MonitorEnter(self); // Lock the object.
	test->watchdog_object_.Get()->NotifyAll(self); // Wake up waiting parties.
	test->watchdog_object_.Get()->MonitorExit(self); // Release the lock.
	}

	thread_pool.StopWorkers(self);
	}


	// First test: throwing an exception when trying to wait in Monitor with another thread.
	TEST_F(MonitorTest, CheckExceptionsWait1) {
	// Make the CreateTask wait 10ms, the UseTask wait 10ms.
	// => The use task will get the lock first and get to self == owner check.
	// This will lead to OOM and monitor error messages in the log.
	ScopedLogSeverity sls(LogSeverity::FATAL);
	CommonWaitSetup(this, class_linker_, 10, 50, false, false, 2, 50, true,
	"Monitor test thread pool 1");
	}

	// Second test: throwing an exception for invalid wait time.
	TEST_F(MonitorTest, CheckExceptionsWait2) {
	// Make the CreateTask wait 0ms, the UseTask wait 10ms.
	// => The create task will get the lock first and get to ms >= 0
	// This will lead to OOM and monitor error messages in the log.
	ScopedLogSeverity sls(LogSeverity::FATAL);
	CommonWaitSetup(this, class_linker_, 0, -1, true, false, 10, 50, true,
	"Monitor test thread pool 2");
	}

	// Third test: throwing an interrupted-exception.
	TEST_F(MonitorTest, CheckExceptionsWait3) {
	// Make the CreateTask wait 0ms, then Wait for a long time. Make the InterruptTask wait 10ms,
	// after which it will interrupt the create task and then wait another 10ms.
	// => The create task will get to the interrupted-exception throw.
	// This will lead to OOM and monitor error messages in the log.
	ScopedLogSeverity sls(LogSeverity::FATAL);
	CommonWaitSetup(this, class_linker_, 0, 500, true, true, 10, 50, true,
	"Monitor test thread pool 3");
	}

	class TryLockTask : public Task {
	public:
	explicit TryLockTask(Handle<mirror::Object> obj) : obj_(obj) {}

	void Run(Thread* self) {
	ScopedObjectAccess soa(self);
	// Lock is held by other thread, try lock should fail.
	ObjectTryLock<mirror::Object> lock(self, obj_);
	EXPECT_FALSE(lock.Acquired());
	}

	void Finalize() {
	delete this;
	}

	private:
	Handle<mirror::Object> obj_;
	};

	// Test trylock in deadlock scenarios.
	TEST_F(MonitorTest, TestTryLock) {
	ScopedLogSeverity sls(LogSeverity::FATAL);

	Thread* const self = Thread::Current();
	ThreadPool thread_pool("the pool", 2);
	ScopedObjectAccess soa(self);
	StackHandleScope<1> hs(self);
	Handle<mirror::Object> obj1(
	hs.NewHandle<mirror::Object>(mirror::String::AllocFromModifiedUtf8(self, "hello, world!")));
	{
	ObjectLock<mirror::Object> lock1(self, obj1);
	{
	ObjectTryLock<mirror::Object> trylock(self, obj1);
	EXPECT_TRUE(trylock.Acquired());
	}
	// Test failure case.
	thread_pool.AddTask(self, new TryLockTask(obj1));
	thread_pool.StartWorkers(self);
	ScopedThreadSuspension sts(self, kSuspended);
	thread_pool.Wait(Thread::Current(), /do_work/false, /may_hold_locks/false);
	}
	// Test that the trylock actually locks the object.
	{
	ObjectTryLock<mirror::Object> trylock(self, obj1);
	EXPECT_TRUE(trylock.Acquired());
	obj1->Notify(self);
	// Since we hold the lock there should be no monitor state exeception.
	self->AssertNoPendingException();
	}
	thread_pool.StopWorkers(self);
	}


	} // namespace art