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 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.
