2 files changed, 13 insertions, 6 deletions
diff --git a/base/threading/thread.h b/base/threading/thread.h
index d7451ec..2ee4fa2 100644
--- a/base/threading/thread.h
+++ b/base/threading/thread.h
@@ -21,6 +21,8 @@ namespace base {
 // pending tasks queued on the thread's message loop will run to completion
 // before the thread is terminated.
 //
+// NOTE: Subclasses must call Stop() in their destructor. See ~Thread below.
+//
 // After the thread is stopped, the destruction sequence is:
 //
 //  (1) Thread::CleanUp()
@@ -48,9 +50,13 @@ class BASE_EXPORT Thread : PlatformThread::Delegate {
 
   // Destroys the thread, stopping it if necessary.
   //
-  // NOTE: If you are subclassing from Thread, and you wish for your CleanUp
-  // method to be called, then you need to call Stop() from your destructor.
-  //
+  // NOTE: All subclasses of Thread must call Stop() in their
+  // destructor, or otherwise ensure Stop() is called before the
+  // subclass is destructed.  This is required to avoid a data race
+  // between the destructor modifying the vtable, and the thread's
+  // ThreadMain calling the virtual method Run.  It also ensures that
+  // the CleanUp() virtual method is called on the subclass before it
+  // is destructed.
   virtual ~Thread();
 
   // Starts the thread.  Returns true if the thread was successfully started;
diff --git a/base/threading/thread_unittest.cc b/base/threading/thread_unittest.cc
index fe39627..68a24cf 100644
--- a/base/threading/thread_unittest.cc
+++ b/base/threading/thread_unittest.cc
@@ -1,4 +1,4 @@
-// Copyright (c) 2006-2008 The Chromium Authors. All rights reserved.
+// Copyright (c) 2011 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.
 
@@ -48,7 +48,9 @@ class SleepInsideInitThread : public Thread {
     ANNOTATE_BENIGN_RACE(
         this, "Benign test-only data race on vptr - http://crbug.com/98219");
   }
-  virtual ~SleepInsideInitThread() { }
+  virtual ~SleepInsideInitThread() {
+    Stop();
+  }
 
   virtual void Init() {
     base::PlatformThread::Sleep(500);
@@ -85,7 +87,6 @@ class CaptureToEventList : public Thread {
   }
 
   virtual ~CaptureToEventList() {
-    // Must call Stop() manually to have our CleanUp() function called.
     Stop();
   }