From 13f383ff5fc8ff095501794d4ce758f0067ff9b5 Mon Sep 17 00:00:00 2001
From: "darin@chromium.org"
 <darin@chromium.org@0039d316-1c4b-4281-b951-d872f2087c98>
Date: Mon, 28 Sep 2009 18:12:55 +0000
Subject: Assert that thread-safe reference counting is used with cross-thread
 NewRunnableMethod.

This assertion caught such an error in VisitedLinkMaster!

My approach, modify RunnableMethodTraits<T> to assert that
when ReleaseCallee happens on a different thread from
RetainCallee that the type supports thread-safe reference
counting.  I do this by adding a static method to both
RefCounted<T> and RefCountedThreadSafe<T>.

This results in a little ugliness in cases where people
implement AddRef and Release by hand (to make the no-ops).
There may be a nicer way to deal with those few cases.

R=brettw
BUG=none
TEST=none

Review URL: http://codereview.chromium.org/251012

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@27379 0039d316-1c4b-4281-b951-d872f2087c98
---
 base/task.h | 34 ++++++++++++++++++++++++++++------
 1 file changed, 28 insertions(+), 6 deletions(-)

(limited to 'base/task.h')

diff --git a/base/task.h b/base/task.h
index c827681..e9da8b3 100644
--- a/base/task.h
+++ b/base/task.h
@@ -205,12 +205,33 @@ class ReleaseTask : public CancelableTask {
 
 template <class T>
 struct RunnableMethodTraits {
-  static void RetainCallee(T* obj) {
+  RunnableMethodTraits() {
+#ifndef NDEBUG
+    origin_thread_id_ = PlatformThread::CurrentId();
+#endif
+  }
+
+  ~RunnableMethodTraits() {
+#ifndef NDEBUG
+    // If destroyed on a separate thread, then we had better have been using
+    // thread-safe reference counting!
+    if (origin_thread_id_ != PlatformThread::CurrentId())
+      DCHECK(T::ImplementsThreadSafeReferenceCounting());
+#endif
+  }
+
+  void RetainCallee(T* obj) {
     obj->AddRef();
   }
-  static void ReleaseCallee(T* obj) {
+
+  void ReleaseCallee(T* obj) {
     obj->Release();
   }
+
+ private:
+#ifndef NDEBUG
+  PlatformThreadId origin_thread_id_;
+#endif
 };
 
 // RunnableMethod and RunnableFunction -----------------------------------------
@@ -240,13 +261,13 @@ struct RunnableMethodTraits {
 // RunnableMethod and NewRunnableMethod implementation -------------------------
 
 template <class T, class Method, class Params>
-class RunnableMethod : public CancelableTask,
-                       public RunnableMethodTraits<T> {
+class RunnableMethod : public CancelableTask {
  public:
   RunnableMethod(T* obj, Method meth, const Params& params)
       : obj_(obj), meth_(meth), params_(params) {
-    RetainCallee(obj_);
+    traits_.RetainCallee(obj_);
   }
+
   ~RunnableMethod() {
     ReleaseCallee();
   }
@@ -263,7 +284,7 @@ class RunnableMethod : public CancelableTask,
  private:
   void ReleaseCallee() {
     if (obj_) {
-      RunnableMethodTraits<T>::ReleaseCallee(obj_);
+      traits_.ReleaseCallee(obj_);
       obj_ = NULL;
     }
   }
@@ -271,6 +292,7 @@ class RunnableMethod : public CancelableTask,
   T* obj_;
   Method meth_;
   Params params_;
+  RunnableMethodTraits<T> traits_;
 };
 
 template <class T, class Method>
-- 
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