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

Source/platform/heap/ThreadState.h

 /*
  * 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 16 matching lines @@
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
 #ifndef ThreadState_h
 #define ThreadState_h
 
 #include "platform/PlatformExport.h"
 #include "platform/heap/AddressSanitizer.h"
 #include "public/platform/WebThread.h"
+#include "wtf/HashMap.h"
 #include "wtf/HashSet.h"
 #include "wtf/OwnPtr.h"
 #include "wtf/PassOwnPtr.h"
 #include "wtf/ThreadSpecific.h"
 #include "wtf/Threading.h"
 #include "wtf/ThreadingPrimitives.h"
 #include "wtf/Vector.h"
 
-#if ENABLE(GC_PROFILE_HEAP)
-#include "wtf/HashMap.h"
-#endif
-
 namespace blink {
 
 class BaseHeap;
 class BaseHeapPage;
 class FinalizedHeapObjectHeader;
 struct GCInfo;
 class HeapContainsCache;
 class HeapObjectHeader;
 class PageMemory;
 class PersistentNode;
@@ skipping 65 matching lines @@
         class Class;                                                    \
     }                                                                   \
     namespace blink {                                                 \
         template<> struct ThreadingTrait<Namespace::Class> {            \
             static const ThreadAffinity Affinity = AnyThread;           \
         };                                                              \
     }
 
 template<typename U> class ThreadingTrait<const U> : public ThreadingTrait<U> { };
 
+// Declare that a class has a pre-finalizer function.  The function is called in
+// the object's owner thread, and can access Member<>s to other
+// garbarge-collected objects allocated in the thread.  However we must not

[Erik Corry, 2014/10/06 12:39:18]

garbarge -> garbage

[tkent, 2014/10/07 05:10:08]

will fix.

+// allocate new garbage-collected objects, nor update Member<> and Persistent<>
+// pointers.
+//
+// This feature is similar to the HeapHashMap<WeakMember<Foo>, OwnPtr<Disposer>>
+// idiom.  The difference between this and the idiom is that pre-finalizer
+// function is called whenever an object is destructed with this feature.  The
+// HeapHashMap<WeakMember...> idiom requires an assumption that the HeapHashMap
+// outlives objects pointed by WeakMembers.

[Erik Corry, 2014/10/06 12:39:18]

This does not make sense to me.  I'm also not happy with the dots in
"HeapHashMap<WeakMember...>".  Are you suggesting removing all weak heap hash
maps, or only the ones with OwnPtr on the right?

You only need the assumption that the map outlives the Foo objects if you are
going to access the map from the destructor of the Disposer. Otherwise there is
no issue.

As for overhead, if you are going to remove items from the map one at a time
from the pre-finalizer function, then that can be quite a big overhead.  With a
weak map solution, when the map dies, the items are not removed, we just call
the Disposer destuctors.

[haraken, 2014/10/06 12:54:05]

We're just planning to remove the weak hash maps that have Disposers on the
right. The Disposer pattern looks complicated, so we don't have two ways (i.e.,
the Disposer pattern and the pre-finalizer idiom) to achieve the same thing.
Yeah. That being said, there are ~10 Disposers in the code base, so I hope the
overhead won't become an issue.

[tkent, 2014/10/07 05:10:08]

The latter.  I'll update the comment.
Right.
ThreadState::invokePreFinalizers() might have a performance issue because
HashMap::removeAll() can shrink repeatedly.
We should optimize this if this is significant.

+// FIXME: Replace all of the HeapHashMap<WeakMember<Foo>, OwnPtr<Disposer>>
+// idiom usages with the pre-finalizer.
+//
+// See ThreadState::registerPreFinalizer.
+//
+// Usage:
+//
+// class Foo : GarbageCollected<Foo> {
+//     USING_PRE_FINALIZER(Foo, dispose);
+// public:
+//     Foo()
+//     {
+//         ThreadState::current()->registerPreFinalizer(*this);
+//     }
+// private:
+//     void dispose();
+//     Member<Bar> m_bar;
+// };
+//
+// void Foo::dispose()
+// {
+//     m_bar->...
+// }
+#define USING_PRE_FINALIZER(Class, method)   \
+    public: \
+        static bool invokePreFinalizer(void* object, Visitor& visitor)   \
+        { \
+            Class* self = reinterpret_cast<Class*>(object); \
+            if (visitor.isAlive(self)) \
+                return false; \
+            self->method(); \
+            return true; \
+        } \
+        typedef char UsingPreFinazlizerMacroNeedsTrailingSemiColon
+
 // List of typed heaps. The list is used to generate the implementation
 // of typed heap related methods.
 //
 // To create a new typed heap add a H(<ClassName>) to the
 // FOR_EACH_TYPED_HEAP macro below.
 #define FOR_EACH_TYPED_HEAP(H)  \
     H(Node)
 
 #define TypedHeapEnumName(Type) Type##Heap,
 #define TypedHeapEnumNameNonFinalized(Type) Type##HeapNonFinalized,
@@ skipping 478 matching lines @@
 
     void getStats(HeapStats&);
     HeapStats& stats() { return m_stats; }
     HeapStats& statsAfterLastGC() { return m_statsAfterLastGC; }
 
     void setupHeapsForTermination();
 
     void registerSweepingTask();
     void unregisterSweepingTask();
 
+    // Request to call a pref-finalizer of the target object before the object
+    // is destructed.  The class T must have USING_PRE_FINALIZER().  The
+    // argument should be |*this|.  Registering a lot of objects affects GC
+    // performance.  We should register an object only if the object really
+    // requires pre-finalizer, and we should unregister the object if
+    // pre-finalizer is unnecessary.
+    template<typename T>
+    void registerPreFinalizer(T& target)
+    {
+        ASSERT(!m_preFinalizers.contains(&target));
+        ASSERT(!isSweepInProgress());
+        m_preFinalizers.add(&target, &T::invokePreFinalizer);
+    }
+
+    // Cancel above requests.  The argument should be |*this|.  This function is
+    // ignored if it is called in pre-finalizer functions.
+    template<typename T>
+    void unregisterPreFinalizer(T& target)
+    {
+        ASSERT(&T::invokePreFinalizer);
+        unregisterPreFinalizerInternal(&target);
+    }
+
     Mutex& sweepMutex() { return m_sweepMutex; }
 
 private:
     explicit ThreadState();
     ~ThreadState();
 
     friend class SafePointBarrier;
     friend class SafePointAwareMutexLocker;
 
     void enterSafePoint(StackState, void*);
@@ skipping 18 matching lines @@
     // to sweep away any objects that are left on this heap.
     // We assert that nothing must remain after this cleanup.
     // If assertion does not hold we crash as we are potentially
     // in the dangling pointer situation.
     void cleanup();
     void cleanupPages();
 
     void setLowCollectionRate(bool value) { m_lowCollectionRate = value; }
 
     void waitUntilSweepersDone();
+    void unregisterPreFinalizerInternal(void*);
+    void invokePreFinalizers(Visitor&);
 
     static WTF::ThreadSpecific<ThreadState*>* s_threadSpecific;
     static SafePointBarrier* s_safePointBarrier;
 
     // This variable is flipped to true after all threads are stoped
     // and outermost GC has started.
     static bool s_inGC;
 
     // We can't create a static member of type ThreadState here
     // because it will introduce global constructor and destructor.
@@ skipping 31 matching lines @@
     bool m_isTerminating;
 
     bool m_lowCollectionRate;
 
     OwnPtr<blink::WebThread> m_sweeperThread;
     int m_numberOfSweeperTasks;
     Mutex m_sweepMutex;
     ThreadCondition m_sweepThreadCondition;
 
     CallbackStack* m_weakCallbackStack;
+    HashMap<void*, bool (*)(void*, Visitor&)> m_preFinalizers;
 
 #if defined(ADDRESS_SANITIZER)
     void* m_asanFakeStack;
 #endif
 };
 
 template<ThreadAffinity affinity> class ThreadStateFor;
 
 template<> class ThreadStateFor<MainThreadOnly> {
 public:
@@ skipping 116 matching lines @@
     // whether the page is part of a terminting thread or
     // if the page is traced after being terminated (orphaned).
     uintptr_t m_terminating : 1;
     uintptr_t m_tracedAfterOrphaned : 1;
     uintptr_t m_promptlyFreedSize : 17; // == blinkPageSizeLog2
 };
 
 }
 
 #endif // ThreadState_h