RE: Rfcomm Use Count

Hi Marcel,

> > Making bluez_accept_dequeue() return sockets regardless of 
> state is a
> > potential solution. Accept() for rfcomm and l2cap would 
> then need to be
> > modified to kill already closed sockets. The existing loop 
> in the accept()'s
> > would need to be modified or a new one added to handle
> > bluez_accept_dequeue() not always returning an open socket.
> 
> I don't like that idea and the problem is not in 
> ...cleanup_listen() and
> so I am not sure if it will really help us.

Fair enough. Though I'm talking about changing bluez_accept_dequeue(), not
necessarily cleanup_listen().

> > I may not have been clear about my thoughts on 
> rfcomm_sock_cleanup_listen().
> > If bluez_accept_dequeue() did return sockets regardless of 
> state, then
> > rfcomm_sock_cleanup_listen() should work (unless calling 
> close on an already
> > closed socket causes trouble). When it calls 
> rfcomm_sock_kill(), sock_put()
> > gets called which calls destruct() which should decrement 
> the use count.
> 
> The ...cleanup_listen() kicks in when you stop the listening 
> server, but
> that is far too late. The problematic part already happened. 
> We close a
> connection that wasn't accepted. We must fix it there and not 
> afterwards
> like somekind of garbage collection. This is the kernel and not some
> weird Jave/C++ code.

With my suggestion above the condition would be handled by either accept()
or cleanup_listen(), whichever is called first. Though I guess you could
still consider that to be garbage collection.

> > What if bluez_accept_dequeue() called sk->shutdown() on 
> sockets which are
> > already closed in the accept queue?
> 
> I am not sure about the side effects, but this can be a 
> solution. What I
> think is that setting the socket to BT_CLOSED is wrong. Maybe using
> BT_DISCONN is better, but this involves changing the state machine.

Calling sk->shutdown() is bluez_accept_dequeue() would be virtually the same
timing (i.e. garbage collecting likeness) as the suggestion above (returning
the closed socket in ...accept_dequeue). It would happen only when accept()
or cleanup_listen() are called.

> > I'll try out l2cap later for you. We should see the same thing.
> 
> I am not sure anymore. Maybe this is only RFCOMM related.

I sent another e-mail a moment ago...  It doesn't happen with l2cap (or at
least I wasn't able to get it to happen).

-Daryl.



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