Thread::Stop() must be called before any subclass's destructor completes.

base/threading/thread.h

 // 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.
 
 #ifndef BASE_THREAD_H_
 #define BASE_THREAD_H_
 #pragma once
 
 #include <string>
 
 #include "base/base_export.h"
 #include "base/message_loop.h"
 #include "base/message_loop_proxy.h"
 #include "base/threading/platform_thread.h"
 
 namespace base {
 
 // A simple thread abstraction that establishes a MessageLoop on a new thread.
 // The consumer uses the MessageLoop of the thread to cause code to execute on
 // the thread.  When this object is destroyed the thread is terminated.  All
 // 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()
 //  (2) MessageLoop::~MessageLoop
 //  (3.b)    MessageLoop::DestructionObserver::WillDestroyCurrentMessageLoop
 class BASE_EXPORT Thread : PlatformThread::Delegate {
  public:
   struct Options {
     Options() : message_loop_type(MessageLoop::TYPE_DEFAULT), stack_size(0) {}
     Options(MessageLoop::Type type, size_t size)
         : message_loop_type(type), stack_size(size) {}
 
     // Specifies the type of message loop that will be allocated on the thread.
     MessageLoop::Type message_loop_type;
 
     // Specifies the maximum stack size that the thread is allowed to use.
     // This does not necessarily correspond to the thread's initial stack size.
     // A value of 0 indicates that the default maximum should be used.
     size_t stack_size;
   };
 
   // Constructor.
   // name is a display string to identify the thread.
   explicit Thread(const char* name);
 
   // 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;
   // otherwise, returns false.  Upon successful return, the message_loop()
   // getter will return non-null.
   //
   // Note: This function can't be called on Windows with the loader lock held;
   // i.e. during a DllMain, global object construction or destruction, atexit()
   // callback.
   bool Start();
@@ skipping 118 matching lines @@
   std::string name_;
 
   friend class ThreadQuitTask;
 
   DISALLOW_COPY_AND_ASSIGN(Thread);
 };
 
 }  // namespace base
 
 #endif  // BASE_THREAD_H_