[RFR] Instrumentation for Unsafe CAS

[Man Cao]

My main comment is:

+  ScopedReleaseAcquire(oop obj, ptrdiff_t offset):
addr_(AccessInternal::field_addr(obj, offset)) {

This could use "index_oop_from_field_offset_long(obj, offset)", right?

Also discussed with Arthur that when TSAN is disabled at build-time,
the code would still create the ScopedReleaseAcquire object, but
hopefully the C++ compiler will optimize out no-op objects.

Minor comments:

+class ScopedReleaseAcquire {+private:+  void* addr_;

This class should inherit from "public StackObj".
HotSpot style guide
<https://wiki.openjdk.java.net/display/HotSpot/StyleGuide#StyleGuide-Names>
says instance variable name should start with _, so "_addr".

-Man



On Mon, Sep 23, 2019 at 12:52 PM Arthur Eubanks <aeubanks at google.com> wrote:

> webrev: http://cr.openjdk.java.net/~aeubanks/tsancas/webrev.00/index.html
>
> This is fairly self explanatory. I went down the route of using a C++
> class's constructor/destructor for the release/acquire so I didn't have to
> touch the existing code too much.
>