Oilpan: Prepare to move AbstractSQLStatement, SQLStatement, and SQLCallbackWrapper<T> to Oilpan hea…

Source/modules/webdatabase/SQLCallbackWrapper.h

 /*
  * Copyright (C) 2011 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:
  *
  * 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 22 matching lines @@
 #include "wtf/ThreadingPrimitives.h"
 
 namespace WebCore {
 
 // A helper class to safely dereference the callback objects held by
 // SQLStatement and SQLTransaction on the proper thread. The 'wrapped'
 // callback is dereferenced:
 // - by destructing the enclosing wrapper - on any thread
 // - by calling clear() - on any thread
 // - by unwrapping and then dereferencing normally - on context thread only
+// Oilpan: ~T must be thread-independent.
 template<typename T> class SQLCallbackWrapper {
+    DISALLOW_ALLOCATION();
 public:
     SQLCallbackWrapper(PassOwnPtr<T> callback, ExecutionContext* executionContext)
         : m_callback(callback)
         , m_executionContext(m_callback ? executionContext : 0)
     {
         ASSERT(!m_callback || (m_executionContext.get() && m_executionContext->isContextThread()));
     }
 
     ~SQLCallbackWrapper()
     {
         clear();
     }
 
+    // FIXME: Oilpan: Trace m_executionContext.
+    void trace(Visitor* visitor) { }
+
     void clear()
     {
+#if ENABLE(OILPAN)
+        // It's safe to call ~T in non-context-thread.
+        // Implementation classes of ExecutionContext are on-heap. Their
+        // destructors are called in their owner threads.
+        MutexLocker locker(m_mutex);
+        m_callback.clear();
+        m_executionContext.clear();
+#else
         ExecutionContext* context;
         OwnPtr<T> callback;
         {
             MutexLocker locker(m_mutex);
             if (!m_callback) {
                 ASSERT(!m_executionContext);
                 return;
             }
             if (m_executionContext->isContextThread()) {
                 m_callback.clear();
                 m_executionContext.clear();
                 return;
             }
             context = m_executionContext.release().leakRef();
             callback = m_callback.release();
         }
         context->postTask(SafeReleaseTask::create(callback.release()));
+#endif
     }
 
     PassOwnPtr<T> unwrap()
     {
         MutexLocker locker(m_mutex);
         ASSERT(!m_callback || m_executionContext->isContextThread());
         m_executionContext.clear();
         return m_callback.release();
     }
 
     // Useful for optimizations only, please test the return value of unwrap to be sure.
     bool hasCallback() const { return m_callback; }
 
 private:
+#if !ENABLE(OILPAN)
     class SafeReleaseTask : public ExecutionContextTask {
     public:
         static PassOwnPtr<SafeReleaseTask> create(PassOwnPtr<T> callbackToRelease)
         {
             return adoptPtr(new SafeReleaseTask(callbackToRelease));
         }
 
         virtual void performTask(ExecutionContext* context)
         {
             ASSERT(m_callbackToRelease && context && context->isContextThread());
             m_callbackToRelease.clear();
             context->deref();
         }
 
         virtual bool isCleanupTask() const { return true; }
 
     private:
         explicit SafeReleaseTask(PassOwnPtr<T> callbackToRelease)
             : m_callbackToRelease(callbackToRelease)
         {
         }
 
         OwnPtr<T> m_callbackToRelease;
     };
+#endif
 
     Mutex m_mutex;
     OwnPtr<T> m_callback;
     RefPtr<ExecutionContext> m_executionContext;
 };
 
 } // namespace WebCore
 
 #endif // SQLCallbackWrapper_h