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https://issues.apache.org/jira/browse/DERBY-3980?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12655583#action_12655583
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Knut Anders Hatlen commented on DERBY-3980:
-------------------------------------------
Just a guess here, since I haven't checked the details. In the inner
for loop of Deadlock.look(), there's some code to prevent false
positives for self-deadlocks:
// We could be seeing a situation here like
// Granted T1{S}, T2{S}
// Waiting T1{X} - deadlock checking on this
//
// In this case it's not a deadlock, although it
// depends on the locking policy of the Lockable. E.g.
.
.
.
if (lock.canSkip) {
// not a deadlock ...
chain.push(space); // set up as rollback() expects.
rollback(chain);
continue outer;
}
I'm wondering if this perhaps is too broad. Both the transactions that
are waiting for the X lock already have a shared lock on the row, so
they'll both have lock.canSkip==true. We may be giving up finding a
deadlock along that path too early.
> Conflicting select then update with REPEATABLE_READ gives lock timeout
> instead of deadlock
> ------------------------------------------------------------------------------------------
>
> Key: DERBY-3980
> URL: https://issues.apache.org/jira/browse/DERBY-3980
> Project: Derby
> Issue Type: Bug
> Components: Store
> Affects Versions: 10.1.3.1, 10.2.2.0, 10.3.3.0, 10.4.2.0, 10.5.0.0
> Reporter: Kathey Marsden
> Attachments: derby.log, derby.log.10_1,
> javacore.20081209.092827.9800.txt, TryTimeout.java, TryTimeout2.java
>
>
> The attached program TryTimeout.java should detect a deadlock but instead
> throws a lock timeout exception. The program has two threads that attempt:
>
> threadConnection.setAutoCommit(false);
> /* set isolation level to repeatable read */
>
> threadConnection.setTransactionIsolation(Connection.TRANSACTION_REPEATABLE_READ);
>
> ResultSet rs = stmt.executeQuery("select * from t where i = 456");
> while (rs.next());
> stmt.executeUpdate("update t set i = 456 where i = 456");
> threadConnection.commit();
> This gives SQLState 40001 (deadlock) with DB2 but a lock timeout with Derby.
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