Re: [Boost-users] [Mutex] behaviour??

From: Yasmina Berber (yasmina.berber_at_[hidden])
Date: 2008-03-13 07:15:19

Yasmina Berber wrote:
> Hi, everybody
> I have a problem to understand mutex behaviour in a server client program .
> basically there are two threads that execute different code in two
> different classes but manipulate the same resource:
> fisrt Class is Subscriber with these members :
>  
> public:
> ACE_Unbounded_Set<client_reference> m_set;
>  typedef boost::recursive_mutex Mutex;
>  typedef boost::recursive_mutex::scoped_lock Lock;
>  Mutex mutex_set;
>
> and methods:
> Subscribe (client_reference) : inserts  (add) a reference client
> to the set
> { ...
>  Lock theScope( mutex_set);
>  m_set.insert (client_reference) 
>   ...
> }
> Unsubscribe(client_reference) : removes a reference client from the set
> { ...
> Lock theScope( mutex_set);
> m_set.remove (client_reference)
> }
>
>
> the second class is Manager that has a shared pointer to Subscriber
> (SubscriberPtr) and does a specific opeartion on each
> client_reference inside a for loop in the method
> Manage()
> { 
> boost::recursive_mutex::scoped_lock scoped_lock(subscriberPtr->mutex_set)
>   for (Subscriber::Set_Iterator iter (subscriberPtr->m_set);  iter.next
> (...) != 0 ; iter.advance ())
>     {
>        specific opeartion on each client reference
>     }
> }
> What happens is that a client can be removed (call to Unsubscribe()) by
> the first thread during the second one is executing manage() : the set
> is not well protected and  this causes of course seg fault.
>
> I probably do something wrong,
> If you need more details please let me know.
> Regards.
>
>
>   
Hi
Could any one help me in this forum?
Thank you