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

[Aleksey Shipilev]

On 06/25/2018 06:00 PM, Aleksey Shipilev wrote:
> 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.

Well, this makes Serial hang with -XX:+UseShenandoahGC -Xmx4g -XX:+UnlockExperimentalVMOptions
-XX:ShenandoahGCHeuristics=traversal. The hang goes away with -XX:-ThreadLocalHandshakes. Please
reinstate the fix back?

-Aleksey