RFR: 8187809: UseMembar should be set true and deprecate the flag

[David Holmes]

Looks good.

One nit below ...

On 9/11/2017 6:48 AM, Robbin Ehn wrote:
> Hi all, please review!
> 
> This patch set the default technique for reading thread state to memory 
> barriers instead of using the asymmetric dekker synchronization on all 
> platforms.

That's not quite an accurate description. The option is to use platform 
memory barriers (+UseMembar) or the memory-serialization-page 
"simulated" memory barrier. We still employ asymmetric Dekker 
synchronization.

Thanks,
David

> We also deprecate the option and starting the removal 
> process. There have been discussion with people involved in all 
> platforms and we will have another discussion before obsoleting the flag 
> to make sure no issue have been found.
> 
> More info in CSR:
> https://bugs.openjdk.java.net/browse/JDK-8187812
> 
> Bug:
> https://bugs.openjdk.java.net/browse/JDK-8187809
> 
> Code:
> http://cr.openjdk.java.net/~rehn/8187809/webrev/
> 
> Thanks, Robbin