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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). Following this checklist to help us incorporate your contribution quickly and easily: - [x] Make sure there is a [JIRA issue](https://issues.apache.org/jira/browse/MNG-7716) filed for the change (usually before you start working on it). Trivial changes like typos do not require a JIRA issue. Your pull request should address just this issue, without pulling in other changes. - [x] Each commit in the pull request should have a meaningful subject line and body. - [x] Format the pull request title like `[MNG-XXX] SUMMARY`, where you replace `MNG-XXX` and `SUMMARY` with the appropriate JIRA issue. - [x] Also format the first line of the commit message like `[MNG-XXX] SUMMARY`. Best practice is to use the JIRA issue title in both the pull request title and in the first line of the commit message. - [x] Write a pull request description that is detailed enough to understand what the pull request does, how, and why. - [x] Run `mvn clean verify` to make sure basic checks pass. A more thorough check will be performed on your pull request automatically. - [ ] You have run the [Core IT][core-its] successfully. If your pull request is about ~20 lines of code you don't need to sign an [Individual Contributor License Agreement](https://www.apache.org/licenses/icla.pdf) if you are unsure please ask on the developers list. To make clear that you license your contribution under the [Apache License Version 2.0, January 2004](http://www.apache.org/licenses/LICENSE-2.0) you have to acknowledge this by using the following check-box. - [x] I hereby declare this contribution to be licenced under the [Apache License Version 2.0, January 2004](http://www.apache.org/licenses/LICENSE-2.0) - [ ] In any other case, please file an [Apache Individual Contributor License Agreement](https://www.apache.org/licenses/icla.pdf). [core-its]: https://maven.apache.org/core-its/core-it-suite/ > 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 -- This message was sent by Atlassian Jira (v8.20.10#820010)