[9] RFR(S): 8065740: compiler/codecache/OverflowCodeCacheTest.java fails with SIGSEGV

[Tobias Hartmann]

Hi,

please review the following patch.

Bug: https://bugs.openjdk.java.net/browse/JDK-8065740
Webrev: http://cr.openjdk.java.net/~thartmann/8065740/webrev.00/

Problem:
The test allocates CodeBlobs in the code cache by using the Whitebox API method
'WhiteBox::allocate_code_blob' introduced by JDK-8059624. The VM crashes while
sweeping because it encounters an allocated but uninitialized CodeBlob in the
code cache (crash happens in NMethodIterator::next_method because we call
'_code_blob->is_nmethod()' on an uninitialised CodeBlob).
The problem is that 'WhiteBox::allocate_code_blob' gives up the CodeCache_lock
before initializing the CodeBlob. This allows the sweeper thread to encounter a
yet uninitialized CodeBlob while iterating over the code cache.

Solution:
I moved the initialization of the CodeBlob into the scope of the CodeCache_lock.
I also fixed some typos and removed a comment that became meaningless with
JDK-8046809.

Testing:
- Failing testcase
- JPRT

Thanks,
Tobias