FULL PRODUCT VERSION :
java version "1.7.0_71"
Java(TM) SE Runtime Environment (build 1.7.0_71-b14)
Java HotSpot(TM) 64-Bit Server VM (build 24.71-b01, mixed mode)


ADDITIONAL OS VERSION INFORMATION :
Linux sexus.law.di.unimi.it 3.16.4-200.fc20.x86_64 #1 SMP Mon Oct 6 12:57:00 UTC 2014 x86_64 x86_64 x86_64 GNU/Linux


A DESCRIPTION OF THE PROBLEM :
When you inspect a heap with jmap jmap -histo:live PID, sometimes jmap encouters a lock and then THE JVM WRITES AN ERROR MESSAGE "VM warning: GC locker is held; pre-dump GC was skipped" ON STANDARD OUTPUT.

THIS IS SO BROKEN, SO STUPID THAT I CANNOT EVEN EXPLAIN. WE POLLUTED A TERABYTE-SIZED RESULT OF A 12-HOUR COMPUTATION JUST BECAUSE WE HAD A LOOK AT THE HEAP.

It is a first-year thing: error messages go to standard error. Please fix this, it's simply ridiculous.

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Use jmap -histo:live on a running process.

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
I DON'T EXPECT AN INSPECTION TOOL TO SCREW UP THE OUTPUT OF MY PROGRAM.

REPRODUCIBILITY :
This bug can be reproduced always.