Added dynamic annotation files into base/...,...

base/singleton.h

 // Copyright (c) 2006-2008 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef BASE_SINGLETON_H_
 #define BASE_SINGLETON_H_
 
 #include "base/at_exit.h"
 #include "base/atomicops.h"
+#include "base/dynamic_annotations.h"
 #include "base/platform_thread.h"
 
 // Default traits for Singleton<Type>. Calls operator new and operator delete on
 // the object. Registers automatic deletion at process exit.
 // Overload if you need arguments or another memory allocation function.
 template<typename Type>
 struct DefaultSingletonTraits {
   // Allocates the object.
   static Type* New() {
     // The parenthesis is very important here; it forces POD type
@@ skipping 89 matching lines @@
   // This class is safe to be constructed and copy-constructed since it has no
   // member.
 
   // Return a pointer to the one true instance of the class.
   static Type* get() {
     // Our AtomicWord doubles as a spinlock, where a value of
     // kBeingCreatedMarker means the spinlock is being held for creation.
     static const base::subtle::AtomicWord kBeingCreatedMarker = 1;
 
     base::subtle::AtomicWord value = base::subtle::NoBarrier_Load(&instance_);
-    if (value != 0 && value != kBeingCreatedMarker)
+    if (value != 0 && value != kBeingCreatedMarker) {
+      // See the corresponding HAPPENS_BEFORE below.
+      ANNOTATE_HAPPENS_AFTER(&instance_);
       return reinterpret_cast<Type*>(value);
+    }
 
     // Object isn't created yet, maybe we will get to create it, let's try...
     if (base::subtle::Acquire_CompareAndSwap(&instance_,
                                              0,
                                              kBeingCreatedMarker) == 0) {
       // instance_ was NULL and is now kBeingCreatedMarker.  Only one thread
       // will ever get here.  Threads might be spinning on us, and they will
       // stop right after we do this store.
       Type* newval = Traits::New();
+
+      // This annotation helps race detectors recognize correct lock-less
+      // synchronization between different threads calling get().
+      // See the corresponding HAPPENS_AFTER below and above.
+      ANNOTATE_HAPPENS_BEFORE(&instance_);
       base::subtle::Release_Store(
           &instance_, reinterpret_cast<base::subtle::AtomicWord>(newval));
 
       if (Traits::kRegisterAtExit)
         base::AtExitManager::RegisterCallback(OnExit, NULL);
 
       return newval;
     }
 
     // We hit a race.  Another thread beat us and either:
     // - Has the object in BeingCreated state
     // - Already has the object created...
     // We know value != NULL.  It could be kBeingCreatedMarker, or a valid ptr.
     // Unless your constructor can be very time consuming, it is very unlikely
     // to hit this race.  When it does, we just spin and yield the thread until
     // the object has been created.
     while (true) {
       value = base::subtle::NoBarrier_Load(&instance_);
       if (value != kBeingCreatedMarker)
         break;
       PlatformThread::YieldCurrentThread();
     }
 
+    // See the corresponding HAPPENS_BEFORE above.
+    ANNOTATE_HAPPENS_AFTER(&instance_);
     return reinterpret_cast<Type*>(value);
   }
 
   // Shortcuts.
   Type& operator*() {
     return *get();
   }
 
   Type* operator->() {
     return get();
   }
 
  private:
   // Adapter function for use with AtExit().  This should be called single
   // threaded, but we might as well take the precautions anyway.
   static void OnExit(void* unused) {
     // AtExit should only ever be register after the singleton instance was
     // created.  We should only ever get here with a valid instance_ pointer.
     Traits::Delete(reinterpret_cast<Type*>(
         base::subtle::NoBarrier_AtomicExchange(&instance_, 0)));
   }
   static base::subtle::AtomicWord instance_;
 };
 
 template <typename Type, typename Traits, typename DifferentiatingType>
 base::subtle::AtomicWord Singleton<Type, Traits, DifferentiatingType>::
     instance_ = 0;
 
 #endif  // BASE_SINGLETON_H_