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 WebCore { 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 90PassRefPtr<DatabaseContext> DatabaseContext::create(ExecutionContext* context) 91{ 92 RefPtr<DatabaseContext> self = adoptRef(new DatabaseContext(context)); 93 self->ref(); // Is deref()-ed on contextDestroyed(). 94 return self.release(); 95} 96 97DatabaseContext::DatabaseContext(ExecutionContext* context) 98 : ActiveDOMObject(context) 99 , m_hasOpenDatabases(false) 100 , m_isRegistered(true) // will register on construction below. 101 , m_hasRequestedTermination(false) 102{ 103 // ActiveDOMObject expects this to be called to set internal flags. 104 suspendIfNeeded(); 105 106 // For debug accounting only. We must do this before we register the 107 // instance. The assertions assume this. 108 DatabaseManager::manager().didConstructDatabaseContext(); 109 110 DatabaseManager::manager().registerDatabaseContext(this); 111} 112 113DatabaseContext::~DatabaseContext() 114{ 115 stopDatabases(); 116 ASSERT(!m_databaseThread || m_databaseThread->terminationRequested()); 117 118 // For debug accounting only. We must call this last. The assertions assume 119 // this. 120 DatabaseManager::manager().didDestructDatabaseContext(); 121} 122 123// This is called if the associated ExecutionContext is destructing while 124// we're still associated with it. That's our cue to disassociate and shutdown. 125// To do this, we stop the database and let everything shutdown naturally 126// because the database closing process may still make use of this context. 127// It is not safe to just delete the context here. 128void DatabaseContext::contextDestroyed() 129{ 130 stopDatabases(); 131 ActiveDOMObject::contextDestroyed(); 132 deref(); // paired with the ref() call on create(). 133} 134 135// stop() is from stopActiveDOMObjects() which indicates that the owner Frame 136// or WorkerThread is shutting down. Initiate the orderly shutdown by stopping 137// the associated databases. 138void DatabaseContext::stop() 139{ 140 stopDatabases(); 141} 142 143PassRefPtr<DatabaseContext> DatabaseContext::backend() 144{ 145 DatabaseContext* backend = static_cast<DatabaseContext*>(this); 146 return backend; 147} 148 149DatabaseThread* DatabaseContext::databaseThread() 150{ 151 if (!m_databaseThread && !m_hasOpenDatabases) { 152 // It's OK to ask for the m_databaseThread after we've requested 153 // termination because we're still using it to execute the closing 154 // of the database. However, it is NOT OK to create a new thread 155 // after we've requested termination. 156 ASSERT(!m_hasRequestedTermination); 157 158 // Create the database thread on first request - but not if at least one database was already opened, 159 // because in that case we already had a database thread and terminated it and should not create another. 160 m_databaseThread = DatabaseThread::create(); 161 m_databaseThread->start(); 162 } 163 164 return m_databaseThread.get(); 165} 166 167bool DatabaseContext::stopDatabases(DatabaseTaskSynchronizer* cleanupSync) 168{ 169 if (m_isRegistered) { 170 DatabaseManager::manager().unregisterDatabaseContext(this); 171 m_isRegistered = false; 172 } 173 174 // Though we initiate termination of the DatabaseThread here in 175 // stopDatabases(), we can't clear the m_databaseThread ref till we get to 176 // the destructor. This is because the Databases that are managed by 177 // DatabaseThread still rely on this ref between the context and the thread 178 // to execute the task for closing the database. By the time we get to the 179 // destructor, we're guaranteed that the databases are destructed (which is 180 // why our ref count is 0 then and we're destructing). Then, the 181 // m_databaseThread RefPtr destructor will deref and delete the 182 // DatabaseThread. 183 184 if (m_databaseThread && !m_hasRequestedTermination) { 185 m_databaseThread->requestTermination(cleanupSync); 186 m_hasRequestedTermination = true; 187 return true; 188 } 189 return false; 190} 191 192bool DatabaseContext::allowDatabaseAccess() const 193{ 194 if (executionContext()->isDocument()) 195 return toDocument(executionContext())->isActive(); 196 ASSERT(executionContext()->isWorkerGlobalScope()); 197 // allowDatabaseAccess is not yet implemented for workers. 198 return true; 199} 200 201SecurityOrigin* DatabaseContext::securityOrigin() const 202{ 203 return executionContext()->securityOrigin(); 204} 205 206bool DatabaseContext::isContextThread() const 207{ 208 return executionContext()->isContextThread(); 209} 210 211} // namespace WebCore 212