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From "Kathey Marsden (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (DERBY-5561) Race conditions in LogicalConnection checking for a null physical connection
Date Wed, 28 Dec 2011 17:58:31 GMT

    [ https://issues.apache.org/jira/browse/DERBY-5561?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13176727#comment-13176727
] 

Kathey Marsden commented on DERBY-5561:
---------------------------------------

Do you have multiple threads accessing the same  connection at the same time?   If so is it
intentional? Typically when that is being done it is not intentional as even if the various
methods were synchronized the two threads would share transaction and other state that would
be difficult to coordinate.


                
> Race conditions in LogicalConnection checking for a null physical connection
> ----------------------------------------------------------------------------
>
>                 Key: DERBY-5561
>                 URL: https://issues.apache.org/jira/browse/DERBY-5561
>             Project: Derby
>          Issue Type: Bug
>          Components: Network Client
>    Affects Versions: 10.8.2.2
>         Environment: Solaris 10
> Glassfish V2.1.1
> ClientXADataSource connection pool
>            Reporter: Brett Bergquist
>
> There are race conditions with checkForNullPhysicalConnection calls in LogicalConnection.
 checkForNullPhysicalConnection is not synchronized and it checks for the member "phsyicalConnection"
which can be cleared by "nullPhsyicalConnection" (which is synchronized) and "close" (which
is synchronized) and "closeWithoutRecyclingToPool" (which is synchronized).
> This affects "nativeSQL", "getAutoCommit", "getTransactionIsolation", "getWarnings",
"isReadOnly", "getCatalog", "getTypeMap", "createStatement", "prepareCall", "prepareStatement",
"setHoldability", "getHoldability", "setSavePoint", "rollBack", "releaseSavePoint", "getSchema",
"setSchema".
> All of these call "checkForNullPhysicalConnection" and then use the member "physicalConnection"
after that call returns.  Because these methods are not synchronized, between the time "checkForNullPhysicalConnectoin"
returns and "physicalConnection" is used, the "physicalConnection" member could be set to
null and then a NPE occurs.
> Probably all of these methods should be changed to synchronized.

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