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https://issues.apache.org/jira/browse/DERBY-6679?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14077665#comment-14077665
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Rick Hillegas commented on DERBY-6679:
--------------------------------------
Thanks, Diogo. There's a bit of defensive code at the beginning of
BaseMonitor.shutdown() which is supposed to prevent the method from being
invoked by more than one caller. So I don't see how more than one caller could
get to the suspicious code block you flagged. Thanks.
> Possible Atomicity Violation in BaseMonitor.shutdown()
> ------------------------------------------------------
>
> Key: DERBY-6679
> URL: https://issues.apache.org/jira/browse/DERBY-6679
> Project: Derby
> Issue Type: Bug
> Components: Services
> Affects Versions: 10.10.2.0
> Environment: all
> Reporter: Diogo Sousa
> Priority: Minor
>
> I'm developing a tool for atomicity violation detection and I think it have
> found an atomicity violations in derby.
> In org.apache.derby.impl.services.monitor.BaseMonitor there might be an
> atomicity violation in method shutdown(), lines 181-206:
> {noformat}
> for ( ; ; ) {
> synchronized (this) {
> 181: position = services.size() - 1;
> if (position == 0)
> break;
> ...
> }
> ...
> }
> ...
> 206: ((TopService) services.get(0)).shutdown();
> {noformat}
> Between the execution of lines 181 and 206 a concurrent thread may remove the
> only remaining service, causing the access to "services" in line 206 to fail.
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