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https://issues.apache.org/jira/browse/MNG-7716?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17695765#comment-17695765
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ASF GitHub Bot commented on MNG-7716:
-------------------------------------
laeubi opened a new pull request, #1028:
URL: https://github.com/apache/maven/pull/1028
If ConcurrencyDependencyGraph#getRootSchedulableBuilds returns an empty list
then MultiThreadedBuilder is locked forever as it never gets a build result
(because nothing is scheduled).
This changes the method, that in such case just the first project is
returned, this might not give the best performance, but ensures that there is
at least one build scheduled and the build-loop can proceed.
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> ConcurrencyDependencyGraph deadlock if no root can be selected
> --------------------------------------------------------------
>
> Key: MNG-7716
> URL: https://issues.apache.org/jira/browse/MNG-7716
> Project: Maven
> Issue Type: Bug
> Reporter: Christoph Läubrich
> Priority: Major
>
> At Tycho we got a bug-report that results in a deadlock when calling the
> tycho-version-plugin:
> https://github.com/eclipse-tycho/tycho/issues/2169
> I debugged the problem and it seems that ConcurrencyDependencyGraph is
> actually the culprit here because it can return an empty list of projects to
> initially build. As no builds are scheduled then the code in the
> MultiThreadedBuilder waits forever for the result, this is what happening
> here:
> * There is one segment {code}org.faktorips:base:pom:23.6.0-SNAPSHOT ->
> [org.eclipse.tycho:tycho-versions-plugin:3.0.4-SNAPSHOT:set-version]{code}
> * This segment has a transitive reactor dependency to {code}MavenProject:
> org.faktorips:codequality-config:23.6.0-SNAPSHOT @
> faktorips.base/codequality-config/pom.xml{code} (this is not a problem
> because we only execute a reactor=true mojo!)
> * So now the loop finds that there is no "independent" project and returns an
> empty list
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