Oilpan: Add support of pre-finalization callback to Oilpan infrastructure.

Source/platform/heap/ThreadState.cpp

 /*
  * Copyright (C) 2013 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:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 1096 matching lines @@
     {
         NoSweepScope scope(this);
 
         // Disallow allocation during weak processing.
         enterNoAllocationScope();
         {
             TRACE_EVENT0("blink_gc", "ThreadState::threadLocalWeakProcessing");
             // Perform thread-specific weak processing.
             while (popAndInvokeWeakPointerCallback(Heap::s_markingVisitor)) { }
         }
+        {
+            TRACE_EVENT0("blink_gc", "ThreadState::invokePreFinalizers");
+            invokePreFinalizers(*Heap::s_markingVisitor);

[haraken, 2014/10/06 01:55:27]

Just to confirm: The main difference between weak callbacks and pre-finalizers
is that pre-finalizers are always called when the target objects die whereas
weak callbacks are not called if the target objects die together with the
observing objects, right? Probably we might want to make the point clearer in
the comment.

+        }
         leaveNoAllocationScope();
 
         // Perform sweeping and finalization.
 
         // Sweeping will recalculate the stats
         m_stats.clear();
 
         // Sweep the non-finalized heap pages on multiple threads.
         // Attempt to load-balance by having the sweeper thread sweep as
         // close to half of the pages as possible.
@@ skipping 113 matching lines @@
     ASSERT(!state->isAtSafePoint());
     state->safePoint(HeapPointersOnStack);
 }
 
 ThreadState::AttachedThreadStateSet& ThreadState::attachedThreads()
 {
     DEFINE_STATIC_LOCAL(AttachedThreadStateSet, threads, ());
     return threads;
 }
 
+void ThreadState::unregisterPreFinalizerInternal(void* target)
+{
+    if (isSweepInProgress())
+        return;
+    auto it = m_preFinalizers.find(target);
+    ASSERT(it != m_preFinalizers.end());
+    m_preFinalizers.remove(it);
+}
+
+void ThreadState::invokePreFinalizers(Visitor& visitor)
+{
+    Vector<void*> deadObjects;
+    for (auto& entry : m_preFinalizers) {
+        if (entry.value(entry.key, visitor))
+            deadObjects.append(entry.key);
+    }
+    m_preFinalizers.removeAll(deadObjects);
+}
+
 #if ENABLE(GC_PROFILE_MARKING)
 const GCInfo* ThreadState::findGCInfoFromAllThreads(Address address)
 {
     bool needLockForIteration = !isAnyThreadInGC();
     if (needLockForIteration)
         threadAttachMutex().lock();
 
     ThreadState::AttachedThreadStateSet& threads = attachedThreads();
     for (ThreadState::AttachedThreadStateSet::iterator it = threads.begin(), end = threads.end(); it != end; ++it) {
         if (const GCInfo* gcInfo = (*it)->findGCInfo(address)) {
             if (needLockForIteration)
                 threadAttachMutex().unlock();
             return gcInfo;
         }
     }
     if (needLockForIteration)
         threadAttachMutex().unlock();
     return 0;
 }
 #endif
 
 }