1. receive status

   sender                         receiver                   receiver
   ACK:CR                          ACK:CR                     ACK:CR

2. sender get EX of TOKEN
   sender get EX of MESSAGE
   sender                          receiver                   receiver
   TOKEN:EX                         ACK:CR                     ACK:CR
   MESSAGE:EX
   ACK:CR

3. sender write LVB.
   sender down-convert MESSAGE from EX to CR
   sender try to get EX of ACK
   [ wait until all receiver has *processed* the MESSAGE ]

                                     [ triggered by bast of ACK ]
                                     receiver get CR of MESSAGE
                                     receiver read LVB
                                     receiver processes the message
				     [ wait finish ]
                                     receiver release ACK

   sender                         receiver                   receiver
   TOKEN:EX                       MESSAGE:CR                 MESSAGE:CR
   MESSAGE:CR
   ACK:EX

4. sender down-convert ACK from EX to CR
   sender release MESSAGE
   sender release TOKEN
				  receiver upconvert to EX of MESSAGE
                                  receiver get CR of ACK
				  receiver release MESSAGE

   sender                        receiver                   receiver
   ACK:CR                         ACK:CR                     ACK:CR
Signed-off-by: Lidong Zhong <lzhong@suse.com>
Signed-off-by: Goldwyn Rodrigues <rgoldwyn@suse.com>