[jboss-jira] [JBoss JIRA] Commented: (JGRP-532) TCP: hangs without FC

[Bela Ban (JIRA)]

    [ http://jira.jboss.com/jira/browse/JGRP-532?page=comments#action_12365487 ] 
            
Bela Ban commented on JGRP-532:
-------------------------------

Not true, also happens when send queues are disabled. What happens is that Connection._send() can block on the TCP write(), as the receiver node set the sliding window to 0. Example: 
- A and B
- A (NAKACK) receives a message from B, acquires a lock on B's NakReceiverWindow and passes the message up.
- In A.STABLE, we determine that we've seen enough bytes, and send down a STABLE message
- The STABLE message blocks on write() (B has temporarily set its sliding window to 0)
- Now all messages from B will not get processed as the lock for B's NRW is held by the blocked write() thread
- Therefore A will send a sliding window size of 0 to B, which will cause B's write() to block 
==> deadlock

> TCP: hangs without FC
> ---------------------
>
>                 Key: JGRP-532
>                 URL: http://jira.jboss.com/jira/browse/JGRP-532
>             Project: JGroups
>          Issue Type: Bug
>            Reporter: Bela Ban
>         Assigned To: Bela Ban
>             Fix For: 2.5
>
>         Attachments: config.txt, tcp.xml, tmp.txt
>
>
> Usually, FC is enabled, but when FC is not present, perf.Test with 2 senders and the attached tcp.xml/config.txt hangs. Stack trace attached too.

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