[jboss-jira] [JBoss JIRA] Created: (JGRP-447) Non-thread-safe access to FC.creditors

[Brian Stansberry (JIRA)]

Non-thread-safe access to FC.creditors
--------------------------------------

                 Key: JGRP-447
                 URL: http://jira.jboss.com/jira/browse/JGRP-447
             Project: JGroups
          Issue Type: Bug
    Affects Versions: 2.4.1 SP1
            Reporter: Brian Stansberry
         Assigned To: Bela Ban


During load testing of AS HttpSession repl, QE saw RPC transmission errors with the following root cause:

[JBoss] Caused by: java.lang.IndexOutOfBoundsException: Index: 1, Size: 1
[JBoss] at java.util.ArrayList.RangeCheck(ArrayList.java:546)
[JBoss] at java.util.ArrayList.get(ArrayList.java:321)
[JBoss] at org.jgroups.protocols.FC.handleDownMessage(FC.java:390)
[JBoss] at org.jgroups.protocols.FC.down(FC.java:320)
[JBoss] at org.jgroups.stack.Protocol.receiveDownEvent(Protocol.java:517)
[JBoss] at org.jgroups.protocols.FC.receiveDownEvent(FC.java:314)
[JBoss] at org.jgroups.stack.Protocol.passDown(Protocol.java:551)
[JBoss] at org.jgroups.protocols.FRAG2.down(FRAG2.java:167)
[JBoss] at org.jgroups.stack.Protocol.receiveDownEvent(Protocol.java:517)
[JBoss] at org.jgroups.stack.Protocol.passDown(Protocol.java:551)
[JBoss] at org.jgroups.protocols.pbcast.STATE_TRANSFER.down(STATE_TRANSFER.java:294)
[JBoss] at org.jgroups.stack.Protocol.receiveDownEvent(Protocol.java:517)
[JBoss] at org.jgroups.stack.ProtocolStack.down(ProtocolStack.java:385)
[JBoss] at org.jgroups.JChannel.down(JChannel.java:1231)
[JBoss] at org.jgroups.blocks.MessageDispatcher$ProtocolAdapter.down(MessageDispatcher.java:788)
[JBoss] at org.jgroups.blocks.MessageDispatcher$ProtocolAdapter.passDown(MessageDispatcher.java:765)
[JBoss] at org.jgroups.blocks.RequestCorrelator.sendRequest(RequestCorrelator.java:299)
[JBoss] at org.jgroups.blocks.GroupRequest.doExecute(GroupRequest.java:444)
[JBoss] at org.jgroups.blocks.GroupRequest.execute(GroupRequest.java:193)
[JBoss] at org.jgroups.blocks.MessageDispatcher.castMessage(MessageDispatcher.java:429) 

Having a look at FC, in handleDownMessage(), where the problem occurred, there's this:

Util.release(lock);
try
{
   ...
   for(int i=0; i < creditors.size(); i++) {
      sendCreditRequest((Address)creditors.get(i));
  }
}
....

in handleCredit() there's:

if(Util.acquire(lock)) {
   ...
   if(creditors.size() > 0) {  // we are blocked because we expect credit from one or more members
      creditors.remove(sender);
      ...
   }
   ...
}

If the creditors.remove(sender) call is invoked while the handleDownMessage for loop is looping, there's a possibility of IndexOutOfBoundsException.

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