I have a Maven project build with one module, named jenkins-test. This module contains one test, which fails everytime (assertTrue(false) ). There is a problem when this project is executed with "Execute concurrent builds if necessary" turned on and when multiple jobs are started at same time. Multiple builds start and finish, but some of these jobs are completed succesfully and some are marked as failed. What I see in the build status page is something like this:

(Success) Build #180 (May 12, 2012 8:17:09 PM)
...
Module Builds
jenkins-test (didn't run)

(Success) Build #181 (May 12, 2012 8:17:12 PM)
...
Module Builds
(disabled) jenkins-test (didn't run)

(Unstable) Build #182 (May 12, 2012 8:17:19 PM)
...
Module Builds
jenkins-test (Unstable) #182 (Unstable) #183 (Unstable) #184

Logs show that the builds were executed properly (commit ids are right, and "[ERROR] There are test failures." is there). The next build then gets build number #187.

In my setup I'm using Gerrit and Gerrit Trigger to launch jobs, so when I push multiple commits into Gerrit in one push, Jenkins starts multiple jobs at same time. I don't know if you can duplicate this behavior without Gerrit, though.

Currently MavenModule and MavenModuleSet have their own build numbers, which are increment when a new module is built. These might get mixed up when multiple builds are executed concurrently. Multiple MavenModuletSets are built starting at the same time, and some how the numbering of MavenModules gets out of sync.

The commit in https://github.com/jyrkiput/jenkins/commit/0d076e610b39b215ed34c35a5d4840e56183d5e4 fixes this, but I haven't tested it other cases than mine and I don't think that I'm qualified to change something that is this deeply on the jenkins core The commit probably has some unnecessary bits in it too at the moment. So I don't think that it should be merged