This plugin is basically required by Jenkins at this point, but its presence makes it very difficult for other plugins to create custom QueueTaskDispatchers without creating deadlock in the Jenkins build queue. There needs to be a way for jobs to elect not to be blocked when upstream jobs are in the build queue. This issue actually is causing deadlocks in our build queue very frequently. We have implemented a QueueTaskDispatcher we need which causes builds to block when downstream jobs are in the build queue. We need this so that only each stage in our pipeline tests only one build at a time (since matrix jobs trigger additional jobs later on due to the touchstone filter). This type of QueueTaskDispatcher does basically the opposite of what DependencyQueueDispatcher, and as a result makes Jenkins very prone to queue deadlocks.