[RFR] Instrumentation for Unsafe CAS

[Arthur Eubanks]

New webrev: http://cr.openjdk.java.net/~aeubanks/tsancas/webrev.02

On Mon, Sep 23, 2019 at 2:30 PM Man Cao <manc at google.com> wrote:

> 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?
>
> Went back to the original version but used
index_oop_from_field_offset_long() instead of AccessInternal::field_addr().

> 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".
>
> Done

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

> -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.
>>
>