openjdkjvmti/alloc_manager.cc - platform/art - Git at Google


 /* Copyright (C) 2019 The Android Open Source Project
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This file implements interfaces from the file jvmti.h. This implementation
  * is licensed under the same terms as the file jvmti.h.  The
  * copyright and license information for the file jvmti.h follows.
  *
  * Copyright (c) 2003, 2011, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
  * under the terms of the GNU General Public License version 2 only, as
  * published by the Free Software Foundation.  Oracle designates this
  * particular file as subject to the "Classpath" exception as provided
  * by Oracle in the LICENSE file that accompanied this code.
  *
  * This code is distributed in the hope that it will be useful, but WITHOUT
  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  * version 2 for more details (a copy is included in the LICENSE file that
  * accompanied this code).
  *
  * You should have received a copy of the GNU General Public License version
  * 2 along with this work; if not, write to the Free Software Foundation,
  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  *
  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  * or visit www.oracle.com if you need additional information or have any
  * questions.
  */

 #include "alloc_manager.h"

 #include <atomic>
 #include <sstream>

 #include "base/logging.h"
 #include "gc/allocation_listener.h"
 #include "gc/heap.h"
 #include "handle.h"
 #include "mirror/class-inl.h"
 #include "runtime.h"
 #include "runtime_globals.h"
 #include "scoped_thread_state_change-inl.h"
 #include "scoped_thread_state_change.h"
 #include "thread-current-inl.h"
 #include "thread_list.h"
 #include "thread_pool.h"

 namespace openjdkjvmti {

 template<typename T>
 void AllocationManager::PauseForAllocation(art::Thread* self, T msg) {
   // The suspension can pause us for arbitrary times. We need to do it to sleep unfortunately. So we
   // do test, suspend, test again, sleep, repeat.
   std::string cause;
   const bool is_logging = VLOG_IS_ON(plugin);
   while (true) {
     // We always return when there is no pause and we are runnable.
     art::Thread* pausing_thread = allocations_paused_thread_.load(std::memory_order_seq_cst);
     if (LIKELY(pausing_thread == nullptr || pausing_thread == self)) {
       return;
     }
     if (UNLIKELY(is_logging && cause.empty())) {
       cause = msg();
     }
     art::ScopedThreadSuspension sts(self, art::ThreadState::kSuspended);
     art::MutexLock mu(self, alloc_listener_mutex_);
     pausing_thread = allocations_paused_thread_.load(std::memory_order_seq_cst);
     CHECK_NE(pausing_thread, self) << "We should always be setting pausing_thread = self!"
                                    << " How did this happen? " << *self;
     if (pausing_thread != nullptr) {
       VLOG(plugin) << "Suspending " << *self << " due to " << cause << ". Allocation pause "
                    << "initiated by " << *pausing_thread;
       alloc_pause_cv_.Wait(self);
     }
   }
 }

 extern AllocationManager* gAllocManager;
 AllocationManager* AllocationManager::Get() {
   return gAllocManager;
 }

 void JvmtiAllocationListener::ObjectAllocated(art::Thread* self,
                                               art::ObjPtr<art::mirror::Object>* obj,
                                               size_t cnt) {
   auto cb = manager_->callback_;
   if (cb != nullptr && manager_->callback_enabled_.load(std::memory_order_seq_cst)) {
     cb->ObjectAllocated(self, obj, cnt);
   }
 }

 bool JvmtiAllocationListener::HasPreAlloc() const {
   return manager_->allocations_paused_ever_.load(std::memory_order_seq_cst);
 }

 void JvmtiAllocationListener::PreObjectAllocated(art::Thread* self,
                                                  art::MutableHandle<art::mirror::Class> type,
                                                  size_t* byte_count) {
   manager_->PauseForAllocation(self, [&]() REQUIRES_SHARED(art::Locks::mutator_lock_) {
     std::ostringstream oss;
     oss << "allocating " << *byte_count << " bytes of type " << type->PrettyClass();
     return oss.str();
   });
   if (!type->IsVariableSize()) {
     *byte_count =
         std::max(art::RoundUp(static_cast<size_t>(type->GetObjectSize()), art::kObjectAlignment),
                  *byte_count);
   }
 }

 AllocationManager::AllocationManager()
     : alloc_listener_(nullptr),
       alloc_listener_mutex_("JVMTI Alloc listener",
                             art::LockLevel::kPostUserCodeSuspensionTopLevelLock),
       alloc_pause_cv_("JVMTI Allocation Pause Condvar", alloc_listener_mutex_) {
   alloc_listener_.reset(new JvmtiAllocationListener(this));
 }

 void AllocationManager::DisableAllocationCallback(art::Thread* self) {
   callback_enabled_.store(false);
   DecrListenerInstall(self);
 }

 void AllocationManager::EnableAllocationCallback(art::Thread* self) {
   IncrListenerInstall(self);
   callback_enabled_.store(true);
 }

 void AllocationManager::SetAllocListener(AllocationCallback* callback) {
   CHECK(callback_ == nullptr) << "Already setup!";
   callback_ = callback;
   alloc_listener_.reset(new JvmtiAllocationListener(this));
 }

 void AllocationManager::RemoveAllocListener() {
   callback_enabled_.store(false, std::memory_order_seq_cst);
   callback_ = nullptr;
 }

 void AllocationManager::DecrListenerInstall(art::Thread* self) {
   art::ScopedThreadSuspension sts(self, art::ThreadState::kSuspended);
   art::MutexLock mu(self, alloc_listener_mutex_);
   // We don't need any particular memory-order here since we're under the lock, they aren't
   // changing.
   if (--listener_refcount_ == 0) {
     art::Runtime::Current()->GetHeap()->RemoveAllocationListener();
   }
 }

 void AllocationManager::IncrListenerInstall(art::Thread* self) {
   art::ScopedThreadSuspension sts(self, art::ThreadState::kSuspended);
   art::MutexLock mu(self, alloc_listener_mutex_);
   // We don't need any particular memory-order here since we're under the lock, they aren't
   // changing.
   if (listener_refcount_++ == 0) {
     art::Runtime::Current()->GetHeap()->SetAllocationListener(alloc_listener_.get());
   }
 }

 void AllocationManager::PauseAllocations(art::Thread* self) {
   art::Thread* null_thr = nullptr;
   // Unfortunately once we've paused allocations once we have to leave the listener and
   // PreObjectAlloc event enabled forever. This is to avoid an instance of the ABA problem. We need
   // to make sure that every thread gets a chance to see the PreObjectAlloc event at least once or
   // else it could miss the fact that the object its allocating had its size changed.
   //
   // Consider the following 2 threads. T1 is allocating an object of class K. It is suspended (by
   // user code) somewhere in the AllocObjectWithAllocator function, perhaps while doing a GC to
   // attempt to clear space. With that thread suspended on thread T2 we decide to structurally
   // redefine 'K', changing its size. To do this we insert this PreObjectAlloc event to check and
   // update the size of the class being allocated. This is done successfully. Now imagine if T2
   // removed the listener event then T1 subsequently resumes. T1 would see there is no
   // PreObjectAlloc event and so allocate using the old object size. This leads to it not allocating
   // enough. To prevent this we simply force every allocation after our first pause to go through
   // the PreObjectAlloc event.
   //
   // TODO Technically we could do better than this. We just need to be able to require that all
   // threads within allocation functions go through the PreObjectAlloc at least once after we turn
   // it on. This is easier said than done though since we don't want to place a marker on threads
   // (allocation is just too common) and we can't just have every thread go through the event since
   // there are some threads that never or almost never allocate. We would also need to ensure that
   // this thread doesn't pause waiting for all threads to pass the barrier since the other threads
   // might be suspended. We could accomplish this by storing callbacks on each thread that would do
   // the work. Honestly though this is a debug feature and it doesn't slow things down very much so
   // simply leaving it on forever is simpler and safer.
   bool expected = false;
   if (allocations_paused_ever_.compare_exchange_strong(expected, true, std::memory_order_seq_cst)) {
     IncrListenerInstall(self);
   }
   do {
     PauseForAllocation(self, []() { return "request to pause allocations on other threads"; });
   } while (!allocations_paused_thread_.compare_exchange_strong(
       null_thr, self, std::memory_order_seq_cst));
   // Make sure everything else can see this and isn't in the middle of final allocation.
   // Force every thread to either be suspended or pass through a barrier.
   art::ScopedThreadSuspension sts(self, art::ThreadState::kSuspended);
   art::Barrier barrier(0);
   art::FunctionClosure fc([&](art::Thread* thr ATTRIBUTE_UNUSED) {
     barrier.Pass(art::Thread::Current());
   });
   size_t requested = art::Runtime::Current()->GetThreadList()->RunCheckpoint(&fc);
   barrier.Increment(self, requested);
 }

 void AllocationManager::ResumeAllocations(art::Thread* self) {
   CHECK_EQ(allocations_paused_thread_.load(), self) << "not paused! ";
   // See above for why we don't decr the install count.
   CHECK(allocations_paused_ever_.load(std::memory_order_seq_cst));
   art::ScopedThreadSuspension sts(self, art::ThreadState::kSuspended);
   art::MutexLock mu(self, alloc_listener_mutex_);
   allocations_paused_thread_.store(nullptr, std::memory_order_seq_cst);
   alloc_pause_cv_.Broadcast(self);
 }

 }  // namespace openjdkjvmti

	/* Copyright (C) 2019 The Android Open Source Project
	* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
	*
	* This file implements interfaces from the file jvmti.h. This implementation
	* is licensed under the same terms as the file jvmti.h. The
	* copyright and license information for the file jvmti.h follows.
	*
	* Copyright (c) 2003, 2011, Oracle and/or its affiliates. All rights reserved.
	* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
	*
	* This code is free software; you can redistribute it and/or modify it
	* under the terms of the GNU General Public License version 2 only, as
	* published by the Free Software Foundation. Oracle designates this
	* particular file as subject to the "Classpath" exception as provided
	* by Oracle in the LICENSE file that accompanied this code.
	*
	* This code is distributed in the hope that it will be useful, but WITHOUT
	* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
	* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
	* version 2 for more details (a copy is included in the LICENSE file that
	* accompanied this code).
	*
	* You should have received a copy of the GNU General Public License version
	* 2 along with this work; if not, write to the Free Software Foundation,
	* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
	*
	* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
	* or visit www.oracle.com if you need additional information or have any
	* questions.
	*/

	#include "alloc_manager.h"

	#include <atomic>
	#include <sstream>

	#include "base/logging.h"
	#include "gc/allocation_listener.h"
	#include "gc/heap.h"
	#include "handle.h"
	#include "mirror/class-inl.h"
	#include "runtime.h"
	#include "runtime_globals.h"
	#include "scoped_thread_state_change-inl.h"
	#include "scoped_thread_state_change.h"
	#include "thread-current-inl.h"
	#include "thread_list.h"
	#include "thread_pool.h"

	namespace openjdkjvmti {

	template<typename T>
	void AllocationManager::PauseForAllocation(art::Thread* self, T msg) {
	// The suspension can pause us for arbitrary times. We need to do it to sleep unfortunately. So we
	// do test, suspend, test again, sleep, repeat.
	std::string cause;
	const bool is_logging = VLOG_IS_ON(plugin);
	while (true) {
	// We always return when there is no pause and we are runnable.
	art::Thread* pausing_thread = allocations_paused_thread_.load(std::memory_order_seq_cst);
	if (LIKELY(pausing_thread == nullptr \|\| pausing_thread == self)) {
	return;
	}
	if (UNLIKELY(is_logging && cause.empty())) {
	cause = msg();
	}
	art::ScopedThreadSuspension sts(self, art::ThreadState::kSuspended);
	art::MutexLock mu(self, alloc_listener_mutex_);
	pausing_thread = allocations_paused_thread_.load(std::memory_order_seq_cst);
	CHECK_NE(pausing_thread, self) << "We should always be setting pausing_thread = self!"
	<< " How did this happen? " << *self;
	if (pausing_thread != nullptr) {
	VLOG(plugin) << "Suspending " << *self << " due to " << cause << ". Allocation pause "
	<< "initiated by " << *pausing_thread;
	alloc_pause_cv_.Wait(self);
	}
	}
	}

	extern AllocationManager* gAllocManager;
	AllocationManager* AllocationManager::Get() {
	return gAllocManager;
	}

	void JvmtiAllocationListener::ObjectAllocated(art::Thread* self,
	art::ObjPtr<art::mirror::Object>* obj,
	size_t cnt) {
	auto cb = manager_->callback_;
	if (cb != nullptr && manager_->callback_enabled_.load(std::memory_order_seq_cst)) {
	cb->ObjectAllocated(self, obj, cnt);
	}
	}

	bool JvmtiAllocationListener::HasPreAlloc() const {
	return manager_->allocations_paused_ever_.load(std::memory_order_seq_cst);
	}

	void JvmtiAllocationListener::PreObjectAllocated(art::Thread* self,
	art::MutableHandle<art::mirror::Class> type,
	size_t* byte_count) {
	manager_->PauseForAllocation(self, [&]() REQUIRES_SHARED(art::Locks::mutator_lock_) {
	std::ostringstream oss;
	oss << "allocating " << *byte_count << " bytes of type " << type->PrettyClass();
	return oss.str();
	});
	if (!type->IsVariableSize()) {
	*byte_count =
	std::max(art::RoundUp(static_cast<size_t>(type->GetObjectSize()), art::kObjectAlignment),
	*byte_count);
	}
	}

	AllocationManager::AllocationManager()
	: alloc_listener_(nullptr),
	alloc_listener_mutex_("JVMTI Alloc listener",
	art::LockLevel::kPostUserCodeSuspensionTopLevelLock),
	alloc_pause_cv_("JVMTI Allocation Pause Condvar", alloc_listener_mutex_) {
	alloc_listener_.reset(new JvmtiAllocationListener(this));
	}

	void AllocationManager::DisableAllocationCallback(art::Thread* self) {
	callback_enabled_.store(false);
	DecrListenerInstall(self);
	}

	void AllocationManager::EnableAllocationCallback(art::Thread* self) {
	IncrListenerInstall(self);
	callback_enabled_.store(true);
	}

	void AllocationManager::SetAllocListener(AllocationCallback* callback) {
	CHECK(callback_ == nullptr) << "Already setup!";
	callback_ = callback;
	alloc_listener_.reset(new JvmtiAllocationListener(this));
	}

	void AllocationManager::RemoveAllocListener() {
	callback_enabled_.store(false, std::memory_order_seq_cst);
	callback_ = nullptr;
	}

	void AllocationManager::DecrListenerInstall(art::Thread* self) {
	art::ScopedThreadSuspension sts(self, art::ThreadState::kSuspended);
	art::MutexLock mu(self, alloc_listener_mutex_);
	// We don't need any particular memory-order here since we're under the lock, they aren't
	// changing.
	if (--listener_refcount_ == 0) {
	art::Runtime::Current()->GetHeap()->RemoveAllocationListener();
	}
	}

	void AllocationManager::IncrListenerInstall(art::Thread* self) {
	art::ScopedThreadSuspension sts(self, art::ThreadState::kSuspended);
	art::MutexLock mu(self, alloc_listener_mutex_);
	// We don't need any particular memory-order here since we're under the lock, they aren't
	// changing.
	if (listener_refcount_++ == 0) {
	art::Runtime::Current()->GetHeap()->SetAllocationListener(alloc_listener_.get());
	}
	}

	void AllocationManager::PauseAllocations(art::Thread* self) {
	art::Thread* null_thr = nullptr;
	// Unfortunately once we've paused allocations once we have to leave the listener and
	// PreObjectAlloc event enabled forever. This is to avoid an instance of the ABA problem. We need
	// to make sure that every thread gets a chance to see the PreObjectAlloc event at least once or
	// else it could miss the fact that the object its allocating had its size changed.
	//
	// Consider the following 2 threads. T1 is allocating an object of class K. It is suspended (by
	// user code) somewhere in the AllocObjectWithAllocator function, perhaps while doing a GC to
	// attempt to clear space. With that thread suspended on thread T2 we decide to structurally
	// redefine 'K', changing its size. To do this we insert this PreObjectAlloc event to check and
	// update the size of the class being allocated. This is done successfully. Now imagine if T2
	// removed the listener event then T1 subsequently resumes. T1 would see there is no
	// PreObjectAlloc event and so allocate using the old object size. This leads to it not allocating
	// enough. To prevent this we simply force every allocation after our first pause to go through
	// the PreObjectAlloc event.
	//
	// TODO Technically we could do better than this. We just need to be able to require that all
	// threads within allocation functions go through the PreObjectAlloc at least once after we turn
	// it on. This is easier said than done though since we don't want to place a marker on threads
	// (allocation is just too common) and we can't just have every thread go through the event since
	// there are some threads that never or almost never allocate. We would also need to ensure that
	// this thread doesn't pause waiting for all threads to pass the barrier since the other threads
	// might be suspended. We could accomplish this by storing callbacks on each thread that would do
	// the work. Honestly though this is a debug feature and it doesn't slow things down very much so
	// simply leaving it on forever is simpler and safer.
	bool expected = false;
	if (allocations_paused_ever_.compare_exchange_strong(expected, true, std::memory_order_seq_cst)) {
	IncrListenerInstall(self);
	}
	do {
	PauseForAllocation(self, []() { return "request to pause allocations on other threads"; });
	} while (!allocations_paused_thread_.compare_exchange_strong(
	null_thr, self, std::memory_order_seq_cst));
	// Make sure everything else can see this and isn't in the middle of final allocation.
	// Force every thread to either be suspended or pass through a barrier.
	art::ScopedThreadSuspension sts(self, art::ThreadState::kSuspended);
	art::Barrier barrier(0);
	art::FunctionClosure fc([&](art::Thread* thr ATTRIBUTE_UNUSED) {
	barrier.Pass(art::Thread::Current());
	});
	size_t requested = art::Runtime::Current()->GetThreadList()->RunCheckpoint(&fc);
	barrier.Increment(self, requested);
	}

	void AllocationManager::ResumeAllocations(art::Thread* self) {
	CHECK_EQ(allocations_paused_thread_.load(), self) << "not paused! ";
	// See above for why we don't decr the install count.
	CHECK(allocations_paused_ever_.load(std::memory_order_seq_cst));
	art::ScopedThreadSuspension sts(self, art::ThreadState::kSuspended);
	art::MutexLock mu(self, alloc_listener_mutex_);
	allocations_paused_thread_.store(nullptr, std::memory_order_seq_cst);
	alloc_pause_cv_.Broadcast(self);
	}

	} // namespace openjdkjvmti