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From "Kristian Waagan (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (DERBY-5561) Race conditions in LogicalConnection checking for a null physical connection
Date Thu, 26 Apr 2012 09:47:17 GMT

    [ https://issues.apache.org/jira/browse/DERBY-5561?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13262497#comment-13262497
] 

Kristian Waagan commented on DERBY-5561:
----------------------------------------

Any updates on this issue?
To me the changes look safe and correct. Given that the Connection interface probably won't
see much change, and that writing a test that reliably detects missing synchronization in
future methods (i.e. by using reflection and running  a test pattern for each method) may
be non-trivial, I suggest we commit the patch right away unless Siddharth is planning to write
a test for this shortly.

Siddhart, what's your opinion on this?
                
> 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
>            Assignee: Siddharth Srivastava
>              Labels: derby_triage10_9
>         Attachments: DERBY-5561.patch
>
>
> 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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