1/* 2 * Copyright (C) 2008 Apple Inc. All Rights Reserved. 3 * Copyright (C) 2011 Google, Inc. All Rights Reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * 2. Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in the 12 * documentation and/or other materials provided with the distribution. 13 * 14 * THIS SOFTWARE IS PROVIDED BY APPLE COMPUTER, INC. ``AS IS'' AND ANY 15 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 16 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 17 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE COMPUTER, INC. OR 18 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, 19 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, 20 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR 21 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY 22 * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 23 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE 24 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 25 * 26 */ 27 28#include "config.h" 29#include "modules/webdatabase/DatabaseContext.h" 30 31#include "core/dom/Document.h" 32#include "core/dom/ExecutionContext.h" 33#include "modules/webdatabase/Database.h" 34#include "modules/webdatabase/DatabaseManager.h" 35#include "modules/webdatabase/DatabaseTask.h" 36#include "modules/webdatabase/DatabaseThread.h" 37#include "platform/weborigin/SchemeRegistry.h" 38#include "platform/weborigin/SecurityOrigin.h" 39#include "wtf/Assertions.h" 40 41namespace blink { 42 43// How the DatabaseContext Life-Cycle works? 44// ======================================== 45// ... in other words, who's keeping the DatabaseContext alive and how long does 46// it need to stay alive? 47// 48// The DatabaseContext is referenced from RefPtrs in: 49// 1. ExecutionContext 50// 2. Database 51// 52// At Birth: 53// ======== 54// We create a DatabaseContext only when there is a need i.e. the script tries to 55// open a Database via DatabaseManager::openDatabase(). 56// 57// The DatabaseContext constructor will call ref(). This lets DatabaseContext keep itself alive. 58// Note that paired deref() is called from contextDestroyed(). 59// 60// Once a DatabaseContext is associated with a ExecutionContext, it will 61// live until after the ExecutionContext destructs. This is true even if 62// we don't succeed in opening any Databases for that context. When we do 63// succeed in opening Databases for this ExecutionContext, the Database 64// will re-use the same DatabaseContext. 65// 66// At Shutdown: 67// =========== 68// During shutdown, the DatabaseContext needs to: 69// 1. "outlive" the ExecutionContext. 70// - This is needed because the DatabaseContext needs to remove itself from the 71// ExecutionContext's ActiveDOMObject list and ContextLifecycleObserver 72// list. This removal needs to be executed on the script's thread. Hence, we 73// rely on the ExecutionContext's shutdown process to call 74// stop() and contextDestroyed() to give us a chance to clean these up from 75// the script thread. 76// 77// 2. "outlive" the Databases. 78// - This is because they may make use of the DatabaseContext to execute a close 79// task and shutdown in an orderly manner. When the Databases are destructed, 80// they will deref the DatabaseContext from the DatabaseThread. 81// 82// During shutdown, the ExecutionContext is shutting down on the script thread 83// while the Databases are shutting down on the DatabaseThread. Hence, there can be 84// a race condition as to whether the ExecutionContext or the Databases 85// destruct first. 86// 87// The RefPtrs in the Databases and ExecutionContext will ensure that the 88// DatabaseContext will outlive both regardless of which of the 2 destructs first. 89 90PassRefPtrWillBeRawPtr<DatabaseContext> DatabaseContext::create(ExecutionContext* context) 91{ 92 RefPtrWillBeRawPtr<DatabaseContext> self = adoptRefWillBeNoop(new DatabaseContext(context)); 93 DatabaseManager::manager().registerDatabaseContext(self.get()); 94 return self.release(); 95} 96 97DatabaseContext::DatabaseContext(ExecutionContext* context) 98 : ActiveDOMObject(context) 99 , m_hasOpenDatabases(false) 100 , m_hasRequestedTermination(false) 101{ 102 // ActiveDOMObject expects this to be called to set internal flags. 103 suspendIfNeeded(); 104 105 // For debug accounting only. We must do this before we register the 106 // instance. The assertions assume this. 107 DatabaseManager::manager().didConstructDatabaseContext(); 108} 109 110DatabaseContext::~DatabaseContext() 111{ 112 // For debug accounting only. We must call this last. The assertions assume 113 // this. 114 DatabaseManager::manager().didDestructDatabaseContext(); 115} 116 117void DatabaseContext::trace(Visitor* visitor) 118{ 119#if ENABLE(OILPAN) 120 visitor->trace(m_databaseThread); 121#endif 122} 123 124// This is called if the associated ExecutionContext is destructing while 125// we're still associated with it. That's our cue to disassociate and shutdown. 126// To do this, we stop the database and let everything shutdown naturally 127// because the database closing process may still make use of this context. 128// It is not safe to just delete the context here. 129void DatabaseContext::contextDestroyed() 130{ 131 RefPtrWillBeRawPtr<DatabaseContext> protector(this); 132 stopDatabases(); 133 DatabaseManager::manager().unregisterDatabaseContext(this); 134 ActiveDOMObject::contextDestroyed(); 135} 136 137// stop() is from stopActiveDOMObjects() which indicates that the owner 138// LocalFrame is shutting down. Initiate the orderly shutdown by stopping the 139// associated databases. 140void DatabaseContext::stop() 141{ 142 stopDatabases(); 143} 144 145DatabaseContext* DatabaseContext::backend() 146{ 147 return this; 148} 149 150DatabaseThread* DatabaseContext::databaseThread() 151{ 152 if (!m_databaseThread && !m_hasOpenDatabases) { 153 // It's OK to ask for the m_databaseThread after we've requested 154 // termination because we're still using it to execute the closing 155 // of the database. However, it is NOT OK to create a new thread 156 // after we've requested termination. 157 ASSERT(!m_hasRequestedTermination); 158 159 // Create the database thread on first request - but not if at least one database was already opened, 160 // because in that case we already had a database thread and terminated it and should not create another. 161 m_databaseThread = DatabaseThread::create(); 162 m_databaseThread->start(); 163 } 164 165 return m_databaseThread.get(); 166} 167 168bool DatabaseContext::databaseThreadAvailable() 169{ 170 return databaseThread() && !m_hasRequestedTermination; 171} 172 173void DatabaseContext::stopDatabases() 174{ 175 // Though we initiate termination of the DatabaseThread here in 176 // stopDatabases(), we can't clear the m_databaseThread ref till we get to 177 // the destructor. This is because the Databases that are managed by 178 // DatabaseThread still rely on this ref between the context and the thread 179 // to execute the task for closing the database. By the time we get to the 180 // destructor, we're guaranteed that the databases are destructed (which is 181 // why our ref count is 0 then and we're destructing). Then, the 182 // m_databaseThread RefPtr destructor will deref and delete the 183 // DatabaseThread. 184 185 if (databaseThreadAvailable()) { 186 m_hasRequestedTermination = true; 187 // This blocks until the database thread finishes the cleanup task. 188 m_databaseThread->terminate(); 189 } 190} 191 192bool DatabaseContext::allowDatabaseAccess() const 193{ 194 return toDocument(executionContext())->isActive(); 195} 196 197SecurityOrigin* DatabaseContext::securityOrigin() const 198{ 199 return executionContext()->securityOrigin(); 200} 201 202bool DatabaseContext::isContextThread() const 203{ 204 return executionContext()->isContextThread(); 205} 206 207} // namespace blink 208