Re: [Boost-users] how to wait for a thread until it stopped

From: Ben Hutchings (ben.hutchings_at_[hidden])
Date: 2005-08-10 08:53:07

Christian Henning wrote:

>Hi there, I'm still working on the transistion from an old thread lib
>to the boost thread lib.
>
>I have two threads, the GUI thread and a worker thread. The worker
>thread is always inside a loop that only breaks if someone set the
>flag.
>
>The GUI thread has from time to time to stop the worker thread. This
>is currently done by setting a flag ( _bStop ) and the worker thread
>will eventually stop like:
>
>void run()
>{
>   boost::mutex::scoped_lock oLock( _oRunMutex );
>
>   do
>   {
>      ...
>
>      if( _bStop  )
>         _oRunCondition.wait( oLock );
>
>   } while( _bTerminate == false );
>}
>  
>
You must use "while" rather than "if" to test the condition associated 
with a condition variable because of the possibility of spurious 
wake-ups (and in some cases the possibility of the condition becoming 
false by the time the thread reacquires the mutex).

Also you should not use an initial underscore in the names of global 
variables. It's not clear from this code whether you're using such names 
for global or class member variables.

>I believe that this implemention can lead to deadlocks. But how can I
>implement the behavior that the GUI thread will break until the worker thread has stopped.
>  
>
Use the thread::join function.

Ben.