[jira] [Commented] (MNG-7716) ConcurrencyDependencyGraph deadlock if no root can be selected

["ASF GitHub Bot (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/MNG-7716?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17695747#comment-17695747 ] 

ASF GitHub Bot commented on MNG-7716:
-------------------------------------

laeubi opened a new pull request, #1027:
URL: https://github.com/apache/maven/pull/1027

   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.
   
   If this is merged I can contribute a fix for 3.9.x as well!
   
   This relates to:
   - https://github.com/eclipse-tycho/tycho/issues/2169
   
   The fix for this issue was gently sponsored by [Faktor Zehn GmbH](https://www.faktorzehn.com).
   
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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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