RFR: Barriers for locks rewrite

[Andrew Haley]

On 10/10/16 09:34, Roman Kennke wrote:
> Am Montag, den 10.10.2016, 09:28 +0100 schrieb Andrew Haley:
>> On 10/10/16 09:14, Roman Kennke wrote:
>>>
>>> http://cr.openjdk.java.net/~rkennke/lockbarriers/webrev.00/
>>>
>>> Ok?
>>
>> What to do about AArch64?
> 
> Good point!
> 
> Not doing anything should be safe & conservative.
> 
> If we want to do similar improvement as on x86, seek out all the places
> where we modify the mark word (e.g. grep for mark_offset_in_bytes...
> hopefully we haven't used any 0s in there ;-) ) and place an
> appropriate barrier right before that. In x86, the tricky part was to
> get the interpreter_write_barrier() code correct for use with c1. (Side
> note: I would like to use the stub that's used by C2 for C1 and
> interpreter too... should not be hard). And then remove the early
> write-barriers in the monitorenter/exit code for interpreter and c1.

It's important that AArch64 and x86 don't diverge.  It would be best
if all arch-dependent Shenandoah patches had Aarch64 and x86 code
included.  Failing that, we need to keep a list of such x86 changes so
they can be back-ported.

Andrew.