RFR: JDK-8214097: Rework thread initialization and teardown logic

[Robbin Ehn]

Hi David,

Looks good, thanks!

/Robbin

On 12/19/18 10:21 PM, David Holmes wrote:
> Following on from the preliminary RFR:
> 
> http://mail.openjdk.java.net/pipermail/hotspot-dev/2018-December/035737.html
> 
> I've merged with Kim's changes from 8215097.
> 
> Bug: https://bugs.openjdk.java.net/browse/JDK-8214097
> Webrev: http://cr.openjdk.java.net/~dholmes/8214097/webrev.v2/
> 
> Changes since previous discussion:
> 
> - Replaced Kim's initial_thread_created assertion with a check of 
> Thread::current_or_null, with an explanation
> 
> - Removed NJT list addition at construction time as it's not needed after 8215097.
> 
> - Moved the JavaThread call to this->exit(false); from the end of 
> thread_main_inner to the start of post_run - as Markus suggested. This also 
> necessitated a change to the gtest logic compared to the original as it has to 
> override post_run() now to avoid the exit call.
> 
> - Made get_thread_name_string virtual so that the JavaThread subclasses in the 
> gtest can override it and allow their names to be seen in hs_err files. (Makes 
> debugging so much easier when you know which thread crashed!).
> 
> Testing:
>   - Mach 5 tiers 1 - 3
>   - All runtime tests with:
>     - default GC
>     - ZGC
>     - Shenandoah GC
> - gc/g1
> - gc/serial
> - gc/epsilon
> - gc/shenandoah
> 
> Thanks,
> David