Reland 66791 (change was innocent)...

base/singleton.h

 // Copyright (c) 2010 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_
 #pragma once
 
 #include "base/at_exit.h"
 #include "base/atomicops.h"
 #include "base/third_party/dynamic_annotations/dynamic_annotations.h"
+#include "base/thread_restrictions.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
     // initialization.
     return new Type();
   }
 
   // Destroys the object.
   static void Delete(Type* x) {
     delete x;
   }
 
   // Set to true to automatically register deletion of the object on process
   // exit. See below for the required call that makes this happen.
   static const bool kRegisterAtExit = true;
+
+  // Set to false to disallow access on a non-joinable thread.  This is
+  // different from kRegisterAtExit because StaticMemorySingletonTraits allows
+  // access on non-joinable threads, and gracefully handles this.
+  static const bool kAllowedToAccessOnNonjoinableThread = false;
 };
 
 
 // Alternate traits for use with the Singleton<Type>.  Identical to
 // DefaultSingletonTraits except that the Singleton will not be cleaned up
 // at exit.
 template<typename Type>
 struct LeakySingletonTraits : public DefaultSingletonTraits<Type> {
   static const bool kRegisterAtExit = false;
+  static const bool kAllowedToAccessOnNonjoinableThread = true;
 };
 
 
 // Alternate traits for use with the Singleton<Type>.  Allocates memory
 // for the singleton instance from a static buffer.  The singleton will
 // be cleaned up at exit, but can't be revived after destruction unless
 // the Resurrect() method is called.
 //
 // This is useful for a certain category of things, notably logging and
 // tracing, where the singleton instance is of a type carefully constructed to
@@ skipping 26 matching lines @@
   }
 
   static void Delete(Type* p) {
     base::subtle::NoBarrier_Store(&dead_, 1);
     base::subtle::MemoryBarrier();
     if (p != NULL)
       p->Type::~Type();
   }
 
   static const bool kRegisterAtExit = true;
+  static const bool kAllowedToAccessOnNonjoinableThread = true;
 
   // Exposed for unittesting.
   static void Resurrect() {
     base::subtle::NoBarrier_Store(&dead_, 0);
   }
 
  private:
   static const size_t kBufferSize = (sizeof(Type) +
                                      sizeof(intptr_t) - 1) / sizeof(intptr_t);
   static intptr_t buffer_[kBufferSize];
@@ skipping 71 matching lines @@
 template <typename Type,
           typename Traits = DefaultSingletonTraits<Type>,
           typename DifferentiatingType = Type>
 class Singleton {
  public:
   // 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() {
+    if (!Traits::kAllowedToAccessOnNonjoinableThread)
+      base::ThreadRestrictions::AssertSingletonAllowed();
+
     // 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) {
       // See the corresponding HAPPENS_BEFORE below.
       ANNOTATE_HAPPENS_AFTER(&instance_);
       return reinterpret_cast<Type*>(value);
     }
@@ skipping 60 matching lines @@
     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_