While debugging a JVM performance issue a while back, I encountered the following error when I enabled the DTrace hotspot provider:
$ jinfo -flag +ExtendedDTraceProbes `pgrep java`
590: Unable to open door: target process not responding or HotSpot VM not loaded
After a bit of debugging, I figured out that the jinfo command needs to be run by the user the JVM runs as. Hopefully this will help others who encounter this annoying problem.