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 41 namespace 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 90 PassRefPtr<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 97 DatabaseContext::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 } 112 113 DatabaseContext::~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. 128 void 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. 138 void DatabaseContext::stop() 139 { 140 stopDatabases(); 141 } 142 143 PassRefPtr<DatabaseContext> DatabaseContext::backend() 144 { 145 DatabaseContext* backend = static_cast<DatabaseContext*>(this); 146 return backend; 147 } 148 149 DatabaseThread* 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 } 166 167 bool 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 } 191 192 bool 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 } 200 201 SecurityOrigin* DatabaseContext::securityOrigin() const 202 { 203 return executionContext()->securityOrigin(); 204 } 205 206 bool DatabaseContext::isContextThread() const 207 { 208 return executionContext()->isContextThread(); 209 } 210 211 } // namespace WebCore 212
