RFR (XS): CR 6885297: java -XX:RefDiscoveryPolicy=2 or -XX:TLABWasteTargetPercent=0 causes JVM crash

[John Cuthbertson]

Hi Everyone,

Can I have a couple of volunteers review the changes for this CR? The 
changes can be found at http://cr.openjdk.java.net/~johnc/6885297/webrev.0/.

The problem here was that the values of these flags were not checked 
against an acceptable interval range. With RefDiscoveryPolicy the 
acceptable range was 0 or 1. Passing in the value 2 caused a guarantee 
in referenceProcessor.cpp to trip. The value of TLABWasteTargetPercent 
is used in a division expression in threadLocalAllocationBuffer.cpp when 
setting the target number of TLAB refills between pauses. A value of 0 
gives a divide-by-zero error. The question I have is: should zero be an 
acceptable input value for this flag?

Testing: The failing flag combinations.

Thanks,

JohnC