I right clicked on a dynamic web project and chose configure > enable jax rs 1.1 and Eclipse froze.

I ran jstack on it and noticed this trace:

"main" prio=6 tid=0000000013000800 nid=0xa0705540 in Object.wait() [00000000bfffd000]
java.lang.Thread.State: TIMED_WAITING (on object monitor)
at java.lang.Object.wait(Native Method)

• waiting on <0000000016914448> (a org.eclipse.core.internal.jobs.Semaphore)
  at org.eclipse.core.internal.jobs.Semaphore.acquire(Semaphore.java:39)
• locked <0000000016914448> (a org.eclipse.core.internal.jobs.Semaphore)
  at org.eclipse.core.internal.jobs.JobManager.join(JobManager.java:847)
  at org.eclipse.core.internal.jobs.InternalJob.join(InternalJob.java:380)
  at org.eclipse.core.runtime.jobs.Job.join(Job.java:385)
  at org.jboss.tools.ws.jaxrs.ui.cnf.UriMappingsContentProvider.getChildren(UriMappingsContentProvider.java:67)
  at org.eclipse.ui.internal.navigator.extensions.SafeDelegateTreeContentProvider.getChildren(SafeDelegateTreeContentProvider.java:96)
  at org.eclipse.ui.internal.navigator.extensions.SafeDelegateTreeContentProvider.getChildren(SafeDelegateTreeContentProvider.java:275)
  at org.eclipse.ui.internal.navigator.extensions.SafeDelegateTreeContentProvider.getChildren(SafeDelegateTreeContentProvider.java:94)
  at org.eclipse.ui.internal.navigator.NavigatorContentServiceContentProvider$1.run(NavigatorContentServiceContentProvider.java:152)
  at org.eclipse.core.runtime.SafeRunner.run(SafeRunner.java:42)
  at org.eclipse.ui.internal.navigator.NavigatorContentServiceContentProvider.internalGetChildren(NavigatorContentServiceContentProvider.java:139)
  at org.eclipse.ui.internal.navigator.NavigatorContentServiceContentProvider.getChildren(NavigatorContentServiceContentProvider.java:125)
  at org.eclipse.jface.viewers.AbstractTreeViewer.getRawChildren(AbstractTreeViewer.java:1352)
  at org.eclipse.jface.viewers.TreeViewer.getRawChildren(TreeViewer.java:391)
  at org.eclipse.jface.viewers.StructuredViewer.getFilteredChildren(StructuredViewer.java:917)

Looks like it is forcing a wait or lock on the project ?