RFR(XS): 8028306: nsk stress tests, CodeCache fills, then safepoint asserts

[Albert Noll]

Hi,

could I have reviews for this small patch?

webrev: http://cr.openjdk.java.net/~anoll/8028306/webrev.00/
bug: https://bugs.openjdk.java.net/browse/JDK-8028306

problem: 1) ciEnv::register_method() calls 
CodeCache::handle_full_code_cache() in a
                    block where no safepoints are allowed. However, 
handle_full_code_cache
                    can reach a safepoint since it uses locks.
                 2) I added a check in 'possibly_sweep()' that ensures 
that only compiler threads
                     can sweep the code cache. It can happen that normal 
Java threads can call
                     'possibly_sweep()' via 'handle_full_code_cache()'.
solution:  1) move call to 'handle_full_code_cache()' outside the block 
where no safepoints
                     are allowed
                 2) see above

testing: failing test case passes.


Many thanks in advance,
Albert