[jboss-jira] [JBoss JIRA] Created: (JGRP-829) NAKACK: use CAS to determine whether to acquire the lock in NAKACK

[Bela Ban (JIRA)]

NAKACK: use CAS to determine whether to acquire the lock in NAKACK
------------------------------------------------------------------

                 Key: JGRP-829
                 URL: https://jira.jboss.org/jira/browse/JGRP-829
             Project: JGroups
          Issue Type: Bug
            Reporter: Bela Ban
            Assignee: Bela Ban
             Fix For: 2.7


Currently, we acquire a lock for the NakReceiverWindow for a given  sender S. If we have 20 threads for S, then all will add their message to the NRW, then block on the lock. 1 thread will be acble to acquire the lock, all other 19 will block. When the other threads are finally able to acquire the lock, they will return immediately because the first thread already removed and processed all messages.
GOAL:
There should only be one thread for S acquiring the lock and processing the message for S. In the above example, all 19 threads for S will return immediately without acquiring the lock and without blocking.

SOLUTION:
Use a CAS to determine whether a thread need to acquire the NRW lock or not. If not, return immediately. This way, a thread is available in the pool for other msgs to get processed.

We need to make sure that a thread doesn't return when reading the CAS, and immediately afterwards, the other (processing) thread returns, so we have *no* thread processing the messages !

-- 
This message is automatically generated by JIRA.
-
If you think it was sent incorrectly contact one of the administrators: https://jira.jboss.org/jira/secure/Administrators.jspa
-
For more information on JIRA, see: http://www.atlassian.com/software/jira