Source/WebCore/bindings/v8/DOMDataStore.cpp - WebKit - Git at Google

 /*
  * Copyright (C) 2009 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
  * copyright notice, this list of conditions and the following disclaimer
  * in the documentation and/or other materials provided with the
  * distribution.
  *     * Neither the name of Google Inc. nor the names of its
  * contributors may be used to endorse or promote products derived from
  * this software without specific prior written permission.
  *
  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */

 #include "config.h"
 #include "DOMDataStore.h"

 #include "DOMData.h"

 namespace WebCore {

 // DOM binding algorithm:
 //
 // There are two kinds of DOM objects:
 // 1. DOM tree nodes, such as Document, HTMLElement, ...
 //    there classes implement TreeShared<T> interface;
 // 2. Non-node DOM objects, such as CSSRule, Location, etc.
 //    these classes implement a ref-counted scheme.
 //
 // A DOM object may have a JS wrapper object. If a tree node
 // is alive, its JS wrapper must be kept alive even it is not
 // reachable from JS roots.
 // However, JS wrappers of non-node objects can go away if
 // not reachable from other JS objects. It works like a cache.
 //
 // DOM objects are ref-counted, and JS objects are traced from
 // a set of root objects. They can create a cycle. To break
 // cycles, we do following:
 //   Handles from DOM objects to JS wrappers are always weak,
 // so JS wrappers of non-node object cannot create a cycle.
 //   Before starting a global GC, we create a virtual connection
 // between nodes in the same tree in the JS heap. If the wrapper
 // of one node in a tree is alive, wrappers of all nodes in
 // the same tree are considered alive. This is done by creating
 // object groups in GC prologue callbacks. The mark-compact
 // collector will remove these groups after each GC.
 //
 // DOM objects should be deref-ed from the owning thread, not the GC thread
 // that does not own them. In V8, GC can kick in from any thread. To ensure
 // that DOM objects are always deref-ed from the owning thread when running
 // V8 in multi-threading environment, we do following:
 // 1. Maintain a thread specific DOM wrapper map for each object map.
 //    (We're using TLS support from WTF instead of base since V8Bindings
 //     does not depend on base. We further assume that all child threads
 //     running V8 instances are created by WTF and thus a destructor will
 //     be called to clean up all thread specific data.)
 // 2. When GC happens:
 //    2.1. If the dead object is in GC thread's map, remove the JS reference
 //         and deref the DOM object.
 //    2.2. Otherwise, go through all thread maps to find the owning thread.
 //         Remove the JS reference from the owning thread's map and move the
 //         DOM object to a delayed queue. Post a task to the owning thread
 //         to have it deref-ed from the owning thread at later time.
 // 3. When a thread is tearing down, invoke a cleanup routine to go through
 //    all objects in the delayed queue and the thread map and deref all of
 //    them.


 DOMDataStore::DOMDataStore(DOMData* domData)
     : m_domNodeMap(0)
     , m_domObjectMap(0)
     , m_activeDomObjectMap(0)
 #if ENABLE(SVG)
     , m_domSvgElementInstanceMap(0)
 #endif
     , m_domData(domData)
 {
     WTF::MutexLocker locker(DOMDataStore::allStoresMutex());
     DOMDataStore::allStores().append(this);
 }

 DOMDataStore::~DOMDataStore()
 {
     WTF::MutexLocker locker(DOMDataStore::allStoresMutex());
     DOMDataStore::allStores().remove(DOMDataStore::allStores().find(this));
 }

 DOMDataList& DOMDataStore::allStores()
 {
   DEFINE_STATIC_LOCAL(DOMDataList, staticDOMDataList, ());
   return staticDOMDataList;
 }

 WTF::Mutex& DOMDataStore::allStoresMutex()
 {
     DEFINE_STATIC_LOCAL(WTF::Mutex, staticDOMDataListMutex, ());
     return staticDOMDataListMutex;
 }

 void* DOMDataStore::getDOMWrapperMap(DOMWrapperMapType type)
 {
     switch (type) {
     case DOMNodeMap:
         return m_domNodeMap;
     case DOMObjectMap:
         return m_domObjectMap;
     case ActiveDOMObjectMap:
         return m_activeDomObjectMap;
 #if ENABLE(SVG)
     case DOMSVGElementInstanceMap:
         return m_domSvgElementInstanceMap;
 #endif
     }

     ASSERT_NOT_REACHED();
     return 0;
 }

 // Called when the object is near death (not reachable from JS roots).
 // It is time to remove the entry from the table and dispose the handle.
 void DOMDataStore::weakDOMObjectCallback(v8::Persistent<v8::Value> v8Object, void* domObject)
 {
     v8::HandleScope scope;
     ASSERT(v8Object->IsObject());
     DOMData::handleWeakObject(DOMDataStore::DOMObjectMap, v8::Persistent<v8::Object>::Cast(v8Object), domObject);
 }

 void DOMDataStore::weakActiveDOMObjectCallback(v8::Persistent<v8::Value> v8Object, void* domObject)
 {
     v8::HandleScope scope;
     ASSERT(v8Object->IsObject());
     DOMData::handleWeakObject(DOMDataStore::ActiveDOMObjectMap, v8::Persistent<v8::Object>::Cast(v8Object), domObject);
 }

 void DOMDataStore::weakNodeCallback(v8::Persistent<v8::Value> v8Object, void* domObject)
 {
     ASSERT(WTF::isMainThread());

     Node* node = static_cast<Node*>(domObject);

     WTF::MutexLocker locker(DOMDataStore::allStoresMutex());
     DOMDataList& list = DOMDataStore::allStores();
     for (size_t i = 0; i < list.size(); ++i) {
         DOMDataStore* store = list[i];
         if (store->domNodeMap().removeIfPresent(node, v8Object)) {
             ASSERT(store->domData()->owningThread() == WTF::currentThread());
             node->deref(); // Nobody overrides Node::deref so it's safe
             return; // There might be at most one wrapper for the node in world's maps
         }
     }

     // If not found, it means map for the wrapper has been already destroyed, just dispose the
     // handle and deref the object to fight memory leak.
     v8Object.Dispose();
     node->deref(); // Nobody overrides Node::deref so it's safe
 }

 bool DOMDataStore::IntrusiveDOMWrapperMap::removeIfPresent(Node* obj, v8::Persistent<v8::Data> value)
 {
     ASSERT(obj);
     v8::Persistent<v8::Object>* entry = obj->wrapper();
     if (!entry)
         return false;
     if (*entry != value)
         return false;
     obj->clearWrapper();
     m_table.remove(entry);
     value.Dispose();
     return true;
 }

 #if ENABLE(SVG)

 void DOMDataStore::weakSVGElementInstanceCallback(v8::Persistent<v8::Value> v8Object, void* domObject)
 {
     v8::HandleScope scope;
     ASSERT(v8Object->IsObject());
     DOMData::handleWeakObject(DOMDataStore::DOMSVGElementInstanceMap, v8::Persistent<v8::Object>::Cast(v8Object), static_cast<SVGElementInstance*>(domObject));
 }

 #endif  // ENABLE(SVG)

 } // namespace WebCore
	/*
	* Copyright (C) 2009 Google Inc. All rights reserved.
	*
	* Redistribution and use in source and binary forms, with or without
	* modification, are permitted provided that the following conditions are
	* met:
	*
	* * Redistributions of source code must retain the above copyright
	* notice, this list of conditions and the following disclaimer.
	* * Redistributions in binary form must reproduce the above
	* copyright notice, this list of conditions and the following disclaimer
	* in the documentation and/or other materials provided with the
	* distribution.
	* * Neither the name of Google Inc. nor the names of its
	* contributors may be used to endorse or promote products derived from
	* this software without specific prior written permission.
	*
	* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
	* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
	* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
	* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
	* OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
	* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
	* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
	* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
	* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
	* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
	* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
	*/

	#include "config.h"
	#include "DOMDataStore.h"

	#include "DOMData.h"

	namespace WebCore {

	// DOM binding algorithm:
	//
	// There are two kinds of DOM objects:
	// 1. DOM tree nodes, such as Document, HTMLElement, ...
	// there classes implement TreeShared<T> interface;
	// 2. Non-node DOM objects, such as CSSRule, Location, etc.
	// these classes implement a ref-counted scheme.
	//
	// A DOM object may have a JS wrapper object. If a tree node
	// is alive, its JS wrapper must be kept alive even it is not
	// reachable from JS roots.
	// However, JS wrappers of non-node objects can go away if
	// not reachable from other JS objects. It works like a cache.
	//
	// DOM objects are ref-counted, and JS objects are traced from
	// a set of root objects. They can create a cycle. To break
	// cycles, we do following:
	// Handles from DOM objects to JS wrappers are always weak,
	// so JS wrappers of non-node object cannot create a cycle.
	// Before starting a global GC, we create a virtual connection
	// between nodes in the same tree in the JS heap. If the wrapper
	// of one node in a tree is alive, wrappers of all nodes in
	// the same tree are considered alive. This is done by creating
	// object groups in GC prologue callbacks. The mark-compact
	// collector will remove these groups after each GC.
	//
	// DOM objects should be deref-ed from the owning thread, not the GC thread
	// that does not own them. In V8, GC can kick in from any thread. To ensure
	// that DOM objects are always deref-ed from the owning thread when running
	// V8 in multi-threading environment, we do following:
	// 1. Maintain a thread specific DOM wrapper map for each object map.
	// (We're using TLS support from WTF instead of base since V8Bindings
	// does not depend on base. We further assume that all child threads
	// running V8 instances are created by WTF and thus a destructor will
	// be called to clean up all thread specific data.)
	// 2. When GC happens:
	// 2.1. If the dead object is in GC thread's map, remove the JS reference
	// and deref the DOM object.
	// 2.2. Otherwise, go through all thread maps to find the owning thread.
	// Remove the JS reference from the owning thread's map and move the
	// DOM object to a delayed queue. Post a task to the owning thread
	// to have it deref-ed from the owning thread at later time.
	// 3. When a thread is tearing down, invoke a cleanup routine to go through
	// all objects in the delayed queue and the thread map and deref all of
	// them.


	DOMDataStore::DOMDataStore(DOMData* domData)
	: m_domNodeMap(0)
	, m_domObjectMap(0)
	, m_activeDomObjectMap(0)
	#if ENABLE(SVG)
	, m_domSvgElementInstanceMap(0)
	#endif
	, m_domData(domData)
	{
	WTF::MutexLocker locker(DOMDataStore::allStoresMutex());
	DOMDataStore::allStores().append(this);
	}

	DOMDataStore::~DOMDataStore()
	{
	WTF::MutexLocker locker(DOMDataStore::allStoresMutex());
	DOMDataStore::allStores().remove(DOMDataStore::allStores().find(this));
	}

	DOMDataList& DOMDataStore::allStores()
	{
	DEFINE_STATIC_LOCAL(DOMDataList, staticDOMDataList, ());
	return staticDOMDataList;
	}

	WTF::Mutex& DOMDataStore::allStoresMutex()
	{
	DEFINE_STATIC_LOCAL(WTF::Mutex, staticDOMDataListMutex, ());
	return staticDOMDataListMutex;
	}

	void* DOMDataStore::getDOMWrapperMap(DOMWrapperMapType type)
	{
	switch (type) {
	case DOMNodeMap:
	return m_domNodeMap;
	case DOMObjectMap:
	return m_domObjectMap;
	case ActiveDOMObjectMap:
	return m_activeDomObjectMap;
	#if ENABLE(SVG)
	case DOMSVGElementInstanceMap:
	return m_domSvgElementInstanceMap;
	#endif
	}

	ASSERT_NOT_REACHED();
	return 0;
	}

	// Called when the object is near death (not reachable from JS roots).
	// It is time to remove the entry from the table and dispose the handle.
	void DOMDataStore::weakDOMObjectCallback(v8::Persistent<v8::Value> v8Object, void* domObject)
	{
	v8::HandleScope scope;
	ASSERT(v8Object->IsObject());
	DOMData::handleWeakObject(DOMDataStore::DOMObjectMap, v8::Persistent<v8::Object>::Cast(v8Object), domObject);
	}

	void DOMDataStore::weakActiveDOMObjectCallback(v8::Persistent<v8::Value> v8Object, void* domObject)
	{
	v8::HandleScope scope;
	ASSERT(v8Object->IsObject());
	DOMData::handleWeakObject(DOMDataStore::ActiveDOMObjectMap, v8::Persistent<v8::Object>::Cast(v8Object), domObject);
	}

	void DOMDataStore::weakNodeCallback(v8::Persistent<v8::Value> v8Object, void* domObject)
	{
	ASSERT(WTF::isMainThread());

	Node* node = static_cast<Node*>(domObject);

	WTF::MutexLocker locker(DOMDataStore::allStoresMutex());
	DOMDataList& list = DOMDataStore::allStores();
	for (size_t i = 0; i < list.size(); ++i) {
	DOMDataStore* store = list[i];
	if (store->domNodeMap().removeIfPresent(node, v8Object)) {
	ASSERT(store->domData()->owningThread() == WTF::currentThread());
	node->deref(); // Nobody overrides Node::deref so it's safe
	return; // There might be at most one wrapper for the node in world's maps
	}
	}

	// If not found, it means map for the wrapper has been already destroyed, just dispose the
	// handle and deref the object to fight memory leak.
	v8Object.Dispose();
	node->deref(); // Nobody overrides Node::deref so it's safe
	}

	bool DOMDataStore::IntrusiveDOMWrapperMap::removeIfPresent(Node* obj, v8::Persistent<v8::Data> value)
	{
	ASSERT(obj);
	v8::Persistent<v8::Object>* entry = obj->wrapper();
	if (!entry)
	return false;
	if (*entry != value)
	return false;
	obj->clearWrapper();
	m_table.remove(entry);
	value.Dispose();
	return true;
	}

	#if ENABLE(SVG)

	void DOMDataStore::weakSVGElementInstanceCallback(v8::Persistent<v8::Value> v8Object, void* domObject)
	{
	v8::HandleScope scope;
	ASSERT(v8Object->IsObject());
	DOMData::handleWeakObject(DOMDataStore::DOMSVGElementInstanceMap, v8::Persistent<v8::Object>::Cast(v8Object), static_cast<SVGElementInstance*>(domObject));
	}

	#endif // ENABLE(SVG)

	} // namespace WebCore