Oilpan: DatabaseThread::m_thread should not get destructed during sweeping

Source/modules/webdatabase/DatabaseThread.cpp

 /*
  * Copyright (C) 2007, 2008, 2013 Apple 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:
  *
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
  * 2.  Redistributions in binary form must reproduce the above copyright
@@ skipping 33 matching lines @@
     : m_transactionClient(adoptPtr(new SQLTransactionClient()))
     , m_transactionCoordinator(adoptPtrWillBeNoop(new SQLTransactionCoordinator()))
     , m_cleanupSync(0)
     , m_terminationRequested(false)
 {
 }
 
 DatabaseThread::~DatabaseThread()
 {
     ASSERT(m_openDatabaseSet.isEmpty());
-    // Oilpan: The database thread must have finished its cleanup tasks before
-    // the following clear(). Otherwise, WebThread destructor blocks the caller
-    // thread, and causes a deadlock with ThreadState cleanup.
-    // DatabaseContext::stop() asks the database thread to close all of
-    // databases, and wait until GC heap cleanup of the database thread. So we
-    // can safely destruct WebThread here.
-    m_thread.clear();
+    ASSERT(!m_thread);
 }
 
 void DatabaseThread::trace(Visitor* visitor)
 {
 #if ENABLE(OILPAN)
     visitor->trace(m_openDatabaseSet);
     visitor->trace(m_transactionCoordinator);
 #endif
 }
 
 void DatabaseThread::start()
 {
     if (m_thread)
         return;
     m_thread = WebThreadSupportingGC::create("WebCore: Database");
     m_thread->postTask(new Task(WTF::bind(&DatabaseThread::setupDatabaseThread, this)));
 }
 
 void DatabaseThread::setupDatabaseThread()
 {
     m_thread->attachGC();
 }
 
-void DatabaseThread::requestTermination(TaskSynchronizer *cleanupSync)
+void DatabaseThread::terminate()
 {
-    MutexLocker lock(m_terminationRequestedMutex);
-    ASSERT(!m_terminationRequested);
-    m_terminationRequested = true;
-    m_cleanupSync = cleanupSync;
-    WTF_LOG(StorageAPI, "DatabaseThread %p was asked to terminate\n", this);
-    m_thread->postTask(new Task(WTF::bind(&DatabaseThread::cleanupDatabaseThread, this)));
+    TaskSynchronizer sync;
+    {
+        MutexLocker lock(m_terminationRequestedMutex);
+        ASSERT(!m_terminationRequested);
+        m_terminationRequested = true;
+        m_cleanupSync = &sync;
+        WTF_LOG(StorageAPI, "DatabaseThread %p was asked to terminate\n", this);
+        m_thread->postTask(new Task(WTF::bind(&DatabaseThread::cleanupDatabaseThread, this)));
+    }
+    sync.waitForTaskCompletion();
+    // The WebThread destructor blocks until all the tasks of the database
+    // thread are processed. However, it shouldn't block at all because
+    // the database thread has already finished processing the cleanup task.
+    m_thread.clear();
 }
 
 bool DatabaseThread::terminationRequested() const
 {
     MutexLocker lock(m_terminationRequestedMutex);
     return m_terminationRequested;
 }
 
 void DatabaseThread::cleanupDatabaseThread()
 {
@@ skipping 49 matching lines @@
 
 void DatabaseThread::scheduleTask(PassOwnPtr<DatabaseTask> task)
 {
     ASSERT(m_thread);
     ASSERT(!terminationRequested());
     // WebThread takes ownership of the task.
     m_thread->postTask(task.leakPtr());
 }
 
 } // namespace blink