db-derby-dev mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From "Knut Anders Hatlen (JIRA)" <j...@apache.org>
Subject [jira] Created: (DERBY-3909) Race condition in NetXAResource.removeXaresFromSameRMchain()
Date Sat, 11 Oct 2008 17:19:44 GMT
Race condition in NetXAResource.removeXaresFromSameRMchain()
------------------------------------------------------------

                 Key: DERBY-3909
                 URL: https://issues.apache.org/jira/browse/DERBY-3909
             Project: Derby
          Issue Type: Bug
          Components: Network Client
    Affects Versions: 10.5.0.0
            Reporter: Knut Anders Hatlen
            Assignee: Knut Anders Hatlen


NetXAResource.removeXaresFromSameRMchain() does the following to remove a NetXAResource from
what's logically a singly-linked list:

1) Mark the NetXAResource to remove with a flag (a field called ignoreMe_)
2) Synchronize on an object that protects the linked list
3) Follow the chain of next pointers in the linked list and remove the first flagged object
4) Release synchronization lock obtained in (2)
5) Clear the flag set in (1)

Now, say that two threads (T1 and T2) perform step 1 in parallel. T1 is granted the synchronization
lock in (2), and T2 must wait. T1 traverses the linked list, finds the object flagged by T2
and removes it. Further T1 releases the synchronization lock and clears the flag on the object
it had flagged. This is not the same object that it removed, so when T2 is granted the synchronization
lock, there is no object flagged for removal. As a result, only the object T2 attempted to
remove was in fact removed. The object that T1 flagged for removal is still in the linked
list.

-- 
This message is automatically generated by JIRA.
-
You can reply to this email to add a comment to the issue online.


Mime
View raw message