RFR(S): 7120038: G1: ParallelGCThreads==0 is broken

[John Cuthbertson]

Hi Everyone,

While testing the changes for 7119908 I discovered that running G1 with 
ParallelGCThreads=0 is broken. Can I have a couple of volunteers look 
over the changes fix the issues I discovered? The webrev can be found 
at: http://cr.openjdk.java.net/~johnc/7120038/webrev.0/.

Most of the changes are correcting unguarded references to the work gang 
(which is not created when PGCT==0) and a few assertion failures.

Note: we do have an open RFE to remove code specific to PGCT==0 as it is 
not a typical configuration, but until then...

Testing: GC test suite with/without -XX:ParallelGCThreads=0, 
Kitchensink, jprt.

Thanks,

JohnC