RFR: Re-enable Thread-local handshakes by default in Shenandoah

[Aleksey Shipilev]

On 06/25/2018 05:54 PM, Roman Kennke wrote:
> Back in February we disabled TLHS because it caused compilation
> failures. I tried today, and it doesn't seem to cause problems. I
> propose to re-enable it and stay with defaults, unless we encounter
> problems again.
> 
> Testing: tier3_gc_shenandoah, some specjvm
> 
> Ok?

OK.

-Aleksey