openjdkjvmti/jvmti_weak_table.h - platform/art - Git at Google

 /* Copyright (C) 2017 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.
  */

 #ifndef ART_OPENJDKJVMTI_JVMTI_WEAK_TABLE_H_
 #define ART_OPENJDKJVMTI_JVMTI_WEAK_TABLE_H_

 #include <unordered_map>

 #include "base/globals.h"
 #include "base/macros.h"
 #include "base/mutex.h"
 #include "gc/system_weak.h"
 #include "gc_root-inl.h"
 #include "jvmti.h"
 #include "jvmti_allocator.h"
 #include "mirror/object.h"
 #include "thread-current-inl.h"

 namespace openjdkjvmti {

 class EventHandler;

 // A system-weak container mapping objects to elements of the template type. This corresponds
 // to a weak hash map. For historical reasons the stored value is called "tag."
 template <typename T>
 class JvmtiWeakTable : public art::gc::SystemWeakHolder {
  public:
   JvmtiWeakTable()
       : art::gc::SystemWeakHolder(art::kTaggingLockLevel),
         update_since_last_sweep_(false) {
   }

   // Remove the mapping for the given object, returning whether such a mapping existed (and the old
   // value).
   ALWAYS_INLINE bool Remove(art::ObjPtr<art::mirror::Object> obj, /* out */ T* tag)
       REQUIRES_SHARED(art::Locks::mutator_lock_)
       REQUIRES(!allow_disallow_lock_);
   ALWAYS_INLINE bool RemoveLocked(art::ObjPtr<art::mirror::Object> obj, /* out */ T* tag)
       REQUIRES_SHARED(art::Locks::mutator_lock_)
       REQUIRES(allow_disallow_lock_);

   // Set the mapping for the given object. Returns true if this overwrites an already existing
   // mapping.
   ALWAYS_INLINE virtual bool Set(art::ObjPtr<art::mirror::Object> obj, T tag)
       REQUIRES_SHARED(art::Locks::mutator_lock_)
       REQUIRES(!allow_disallow_lock_);
   ALWAYS_INLINE virtual bool SetLocked(art::ObjPtr<art::mirror::Object> obj, T tag)
       REQUIRES_SHARED(art::Locks::mutator_lock_)
       REQUIRES(allow_disallow_lock_);

   // Return the value associated with the given object. Returns true if the mapping exists, false
   // otherwise.
   bool GetTag(art::ObjPtr<art::mirror::Object> obj, /* out */ T* result)
       REQUIRES_SHARED(art::Locks::mutator_lock_)
       REQUIRES(!allow_disallow_lock_) {
     art::Thread* self = art::Thread::Current();
     art::MutexLock mu(self, allow_disallow_lock_);
     Wait(self);

     return GetTagLocked(self, obj, result);
   }
   bool GetTagLocked(art::ObjPtr<art::mirror::Object> obj, /* out */ T* result)
       REQUIRES_SHARED(art::Locks::mutator_lock_)
       REQUIRES(allow_disallow_lock_) {
     art::Thread* self = art::Thread::Current();
     allow_disallow_lock_.AssertHeld(self);
     Wait(self);

     return GetTagLocked(self, obj, result);
   }

   // Sweep the container. DO NOT CALL MANUALLY.
   ALWAYS_INLINE void Sweep(art::IsMarkedVisitor* visitor)
       REQUIRES_SHARED(art::Locks::mutator_lock_)
       REQUIRES(!allow_disallow_lock_);

   // Return all objects that have a value mapping in tags.
   ALWAYS_INLINE
   jvmtiError GetTaggedObjects(jvmtiEnv* jvmti_env,
                               jint tag_count,
                               const T* tags,
                               /* out */ jint* count_ptr,
                               /* out */ jobject** object_result_ptr,
                               /* out */ T** tag_result_ptr)
       REQUIRES_SHARED(art::Locks::mutator_lock_)
       REQUIRES(!allow_disallow_lock_);

   // Locking functions, to allow coarse-grained locking and amortization.
   ALWAYS_INLINE  void Lock() ACQUIRE(allow_disallow_lock_);
   ALWAYS_INLINE void Unlock() RELEASE(allow_disallow_lock_);
   ALWAYS_INLINE void AssertLocked() ASSERT_CAPABILITY(allow_disallow_lock_);

   ALWAYS_INLINE art::ObjPtr<art::mirror::Object> Find(T tag)
       REQUIRES_SHARED(art::Locks::mutator_lock_)
       REQUIRES(!allow_disallow_lock_);

  protected:
   // Should HandleNullSweep be called when Sweep detects the release of an object?
   virtual bool DoesHandleNullOnSweep() {
     return false;
   }
   // If DoesHandleNullOnSweep returns true, this function will be called.
   virtual void HandleNullSweep([[maybe_unused]] T tag) {}

  private:
   ALWAYS_INLINE
   bool SetLocked(art::Thread* self, art::ObjPtr<art::mirror::Object> obj, T tag)
       REQUIRES_SHARED(art::Locks::mutator_lock_)
       REQUIRES(allow_disallow_lock_);

   ALWAYS_INLINE
   bool RemoveLocked(art::Thread* self, art::ObjPtr<art::mirror::Object> obj, /* out */ T* tag)
       REQUIRES_SHARED(art::Locks::mutator_lock_)
       REQUIRES(allow_disallow_lock_);

   bool GetTagLocked(art::Thread* self, art::ObjPtr<art::mirror::Object> obj, /* out */ T* result)
       REQUIRES_SHARED(art::Locks::mutator_lock_)
       REQUIRES(allow_disallow_lock_) {
     auto it = tagged_objects_.find(art::GcRoot<art::mirror::Object>(obj));
     if (it != tagged_objects_.end()) {
       *result = it->second;
       return true;
     }

     // Performance optimization: To avoid multiple table updates, ensure that during GC we
     // only update once. See the comment on the implementation of GetTagSlowPath.
     if (art::gUseReadBarrier &&
         self != nullptr &&
         self->GetIsGcMarking() &&
         !update_since_last_sweep_) {
       return GetTagSlowPath(self, obj, result);
     }

     return false;
   }

   // Slow-path for GetTag. We didn't find the object, but we might be storing from-pointers and
   // are asked to retrieve with a to-pointer.
   ALWAYS_INLINE
   bool GetTagSlowPath(art::Thread* self, art::ObjPtr<art::mirror::Object> obj, /* out */ T* result)
       REQUIRES_SHARED(art::Locks::mutator_lock_)
       REQUIRES(allow_disallow_lock_);

   // Update the table by doing read barriers on each element, ensuring that to-space pointers
   // are stored.
   ALWAYS_INLINE
   void UpdateTableWithReadBarrier()
       REQUIRES_SHARED(art::Locks::mutator_lock_)
       REQUIRES(allow_disallow_lock_);

   template <bool kHandleNull>
   void SweepImpl(art::IsMarkedVisitor* visitor)
       REQUIRES_SHARED(art::Locks::mutator_lock_)
       REQUIRES(!allow_disallow_lock_);

   enum TableUpdateNullTarget {
     kIgnoreNull,
     kRemoveNull,
     kCallHandleNull
   };

   template <typename Updater, TableUpdateNullTarget kTargetNull>
   void UpdateTableWith(Updater& updater)
       REQUIRES_SHARED(art::Locks::mutator_lock_)
       REQUIRES(allow_disallow_lock_);

   template <typename Storage, class Allocator = JvmtiAllocator<T>>
   struct ReleasableContainer;

   struct HashGcRoot {
     size_t operator()(const art::GcRoot<art::mirror::Object>& r) const
         REQUIRES_SHARED(art::Locks::mutator_lock_) {
       return reinterpret_cast<uintptr_t>(r.Read<art::kWithoutReadBarrier>());
     }
   };

   struct EqGcRoot {
     bool operator()(const art::GcRoot<art::mirror::Object>& r1,
                     const art::GcRoot<art::mirror::Object>& r2) const
         REQUIRES_SHARED(art::Locks::mutator_lock_) {
       return r1.Read<art::kWithoutReadBarrier>() == r2.Read<art::kWithoutReadBarrier>();
     }
   };

   using TagAllocator = JvmtiAllocator<std::pair<const art::GcRoot<art::mirror::Object>, T>>;
   using TagMap = std::unordered_map<art::GcRoot<art::mirror::Object>,
                                     T,
                                     HashGcRoot,
                                     EqGcRoot,
                                     TagAllocator>;

   TagMap tagged_objects_ GUARDED_BY(allow_disallow_lock_) GUARDED_BY(art::Locks::mutator_lock_);
   // To avoid repeatedly scanning the whole table, remember if we did that since the last sweep.
   bool update_since_last_sweep_;
 };

 }  // namespace openjdkjvmti

 #endif  // ART_OPENJDKJVMTI_JVMTI_WEAK_TABLE_H_
	/* Copyright (C) 2017 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.
	*/

	#ifndef ART_OPENJDKJVMTI_JVMTI_WEAK_TABLE_H_
	#define ART_OPENJDKJVMTI_JVMTI_WEAK_TABLE_H_

	#include <unordered_map>

	#include "base/globals.h"
	#include "base/macros.h"
	#include "base/mutex.h"
	#include "gc/system_weak.h"
	#include "gc_root-inl.h"
	#include "jvmti.h"
	#include "jvmti_allocator.h"
	#include "mirror/object.h"
	#include "thread-current-inl.h"

	namespace openjdkjvmti {

	class EventHandler;

	// A system-weak container mapping objects to elements of the template type. This corresponds
	// to a weak hash map. For historical reasons the stored value is called "tag."
	template <typename T>
	class JvmtiWeakTable : public art::gc::SystemWeakHolder {
	public:
	JvmtiWeakTable()
	: art::gc::SystemWeakHolder(art::kTaggingLockLevel),
	update_since_last_sweep_(false) {
	}

	// Remove the mapping for the given object, returning whether such a mapping existed (and the old
	// value).
	ALWAYS_INLINE bool Remove(art::ObjPtr<art::mirror::Object> obj, /* out / T tag)
	REQUIRES_SHARED(art::Locks::mutator_lock_)
	REQUIRES(!allow_disallow_lock_);
	ALWAYS_INLINE bool RemoveLocked(art::ObjPtr<art::mirror::Object> obj, /* out / T tag)
	REQUIRES_SHARED(art::Locks::mutator_lock_)
	REQUIRES(allow_disallow_lock_);

	// Set the mapping for the given object. Returns true if this overwrites an already existing
	// mapping.
	ALWAYS_INLINE virtual bool Set(art::ObjPtr<art::mirror::Object> obj, T tag)
	REQUIRES_SHARED(art::Locks::mutator_lock_)
	REQUIRES(!allow_disallow_lock_);
	ALWAYS_INLINE virtual bool SetLocked(art::ObjPtr<art::mirror::Object> obj, T tag)
	REQUIRES_SHARED(art::Locks::mutator_lock_)
	REQUIRES(allow_disallow_lock_);

	// Return the value associated with the given object. Returns true if the mapping exists, false
	// otherwise.
	bool GetTag(art::ObjPtr<art::mirror::Object> obj, /* out / T result)
	REQUIRES_SHARED(art::Locks::mutator_lock_)
	REQUIRES(!allow_disallow_lock_) {
	art::Thread* self = art::Thread::Current();
	art::MutexLock mu(self, allow_disallow_lock_);
	Wait(self);

	return GetTagLocked(self, obj, result);
	}
	bool GetTagLocked(art::ObjPtr<art::mirror::Object> obj, /* out / T result)
	REQUIRES_SHARED(art::Locks::mutator_lock_)
	REQUIRES(allow_disallow_lock_) {
	art::Thread* self = art::Thread::Current();
	allow_disallow_lock_.AssertHeld(self);
	Wait(self);

	return GetTagLocked(self, obj, result);
	}

	// Sweep the container. DO NOT CALL MANUALLY.
	ALWAYS_INLINE void Sweep(art::IsMarkedVisitor* visitor)
	REQUIRES_SHARED(art::Locks::mutator_lock_)
	REQUIRES(!allow_disallow_lock_);

	// Return all objects that have a value mapping in tags.
	ALWAYS_INLINE
	jvmtiError GetTaggedObjects(jvmtiEnv* jvmti_env,
	jint tag_count,
	const T* tags,
	/* out / jint count_ptr,
	/* out / jobject* object_result_ptr,
	/* out / T* tag_result_ptr)
	REQUIRES_SHARED(art::Locks::mutator_lock_)
	REQUIRES(!allow_disallow_lock_);

	// Locking functions, to allow coarse-grained locking and amortization.
	ALWAYS_INLINE void Lock() ACQUIRE(allow_disallow_lock_);
	ALWAYS_INLINE void Unlock() RELEASE(allow_disallow_lock_);
	ALWAYS_INLINE void AssertLocked() ASSERT_CAPABILITY(allow_disallow_lock_);

	ALWAYS_INLINE art::ObjPtr<art::mirror::Object> Find(T tag)
	REQUIRES_SHARED(art::Locks::mutator_lock_)
	REQUIRES(!allow_disallow_lock_);

	protected:
	// Should HandleNullSweep be called when Sweep detects the release of an object?
	virtual bool DoesHandleNullOnSweep() {
	return false;
	}
	// If DoesHandleNullOnSweep returns true, this function will be called.
	virtual void HandleNullSweep([[maybe_unused]] T tag) {}

	private:
	ALWAYS_INLINE
	bool SetLocked(art::Thread* self, art::ObjPtr<art::mirror::Object> obj, T tag)
	REQUIRES_SHARED(art::Locks::mutator_lock_)
	REQUIRES(allow_disallow_lock_);

	ALWAYS_INLINE
	bool RemoveLocked(art::Thread* self, art::ObjPtr<art::mirror::Object> obj, /* out / T tag)
	REQUIRES_SHARED(art::Locks::mutator_lock_)
	REQUIRES(allow_disallow_lock_);

	bool GetTagLocked(art::Thread* self, art::ObjPtr<art::mirror::Object> obj, /* out / T result)
	REQUIRES_SHARED(art::Locks::mutator_lock_)
	REQUIRES(allow_disallow_lock_) {
	auto it = tagged_objects_.find(art::GcRoot<art::mirror::Object>(obj));
	if (it != tagged_objects_.end()) {
	*result = it->second;
	return true;
	}

	// Performance optimization: To avoid multiple table updates, ensure that during GC we
	// only update once. See the comment on the implementation of GetTagSlowPath.
	if (art::gUseReadBarrier &&
	self != nullptr &&
	self->GetIsGcMarking() &&
	!update_since_last_sweep_) {
	return GetTagSlowPath(self, obj, result);
	}

	return false;
	}

	// Slow-path for GetTag. We didn't find the object, but we might be storing from-pointers and
	// are asked to retrieve with a to-pointer.
	ALWAYS_INLINE
	bool GetTagSlowPath(art::Thread* self, art::ObjPtr<art::mirror::Object> obj, /* out / T result)
	REQUIRES_SHARED(art::Locks::mutator_lock_)
	REQUIRES(allow_disallow_lock_);

	// Update the table by doing read barriers on each element, ensuring that to-space pointers
	// are stored.
	ALWAYS_INLINE
	void UpdateTableWithReadBarrier()
	REQUIRES_SHARED(art::Locks::mutator_lock_)
	REQUIRES(allow_disallow_lock_);

	template <bool kHandleNull>
	void SweepImpl(art::IsMarkedVisitor* visitor)
	REQUIRES_SHARED(art::Locks::mutator_lock_)
	REQUIRES(!allow_disallow_lock_);

	enum TableUpdateNullTarget {
	kIgnoreNull,
	kRemoveNull,
	kCallHandleNull
	};

	template <typename Updater, TableUpdateNullTarget kTargetNull>
	void UpdateTableWith(Updater& updater)
	REQUIRES_SHARED(art::Locks::mutator_lock_)
	REQUIRES(allow_disallow_lock_);

	template <typename Storage, class Allocator = JvmtiAllocator<T>>
	struct ReleasableContainer;

	struct HashGcRoot {
	size_t operator()(const art::GcRoot<art::mirror::Object>& r) const
	REQUIRES_SHARED(art::Locks::mutator_lock_) {
	return reinterpret_cast<uintptr_t>(r.Read<art::kWithoutReadBarrier>());
	}
	};

	struct EqGcRoot {
	bool operator()(const art::GcRoot<art::mirror::Object>& r1,
	const art::GcRoot<art::mirror::Object>& r2) const
	REQUIRES_SHARED(art::Locks::mutator_lock_) {
	return r1.Read<art::kWithoutReadBarrier>() == r2.Read<art::kWithoutReadBarrier>();
	}
	};

	using TagAllocator = JvmtiAllocator<std::pair<const art::GcRoot<art::mirror::Object>, T>>;
	using TagMap = std::unordered_map<art::GcRoot<art::mirror::Object>,
	T,
	HashGcRoot,
	EqGcRoot,
	TagAllocator>;

	TagMap tagged_objects_ GUARDED_BY(allow_disallow_lock_) GUARDED_BY(art::Locks::mutator_lock_);
	// To avoid repeatedly scanning the whole table, remember if we did that since the last sweep.
	bool update_since_last_sweep_;
	};

	} // namespace openjdkjvmti

	#endif // ART_OPENJDKJVMTI_JVMTI_WEAK_TABLE_H_