RFR(S): 8189368: Add information on current bias holder for BiasedLockRevocation event

[David Holmes]

Hi Robin,

On 25/10/2017 11:52 PM, Robin Westberg wrote:
> Hi all,
> 
> Please review the following changes which add a new field to the BiasedLockRevocation event, previousOwner, containing information on which thread (if any) owned the bias before it was revoked.

So to be clear the previous bias owner is only recorded for the case 
where we are doing a direct bias revocation**, at a safepoint and the 
owner thread is still alive - correct?

** By which I mean the only case you don't pass NULL to revoke_bias.

Is it necessary for the thread to still be alive to get the thread-id? 
(If yes then SMR may help here). I was just thinking that it might be 
useful to distinguish the anonymously-biased case from the 
owner-was-dead case.

But overall this seems fine for what it does.

Thanks,
David

> Issue:
> https://bugs.openjdk.java.net/browse/JDK-8189368
> 
> Webrev:
> http://cr.openjdk.java.net/~egahlin/8189368_1/
> 
> Best regards,
> Robin
>