RFR (S) 8074355: make MutexLocker smarter about non-JavaThreads

[coleen.phillimore at oracle.com]

On 4/26/19 12:10 PM, coleen.phillimore at oracle.com wrote:
> Summary: Use safepoint_check_always/safepoint_check_never instead of 
> safepoint_check_sometimes for locks that are taken by JavaThreads and 
> non-JavaThreads
>
> This patch moves all but 3 of the locks to not be 
> safepoint_check_sometimes.  We have plans to fix these three. Also, 
> this patch allows for being explicit about safepoint checking or not 
> when the thread is a non-java thread, which is something that Kim 
> objected to in my first patch.
>
> Tested with mach5 tier1-3.
>
> open webrev at http://cr.openjdk.java.net/~coleenp/2019/8074355.03/webrev
> bug link https://bugs.openjdk.java.net/browse/JDK-8074355
>
> Thanks,
> Coleen
One note about the additional ShutdownTest.  This is an old test that 
was removed that shows that Heap_lock needs to be taken in 
Threads::destroy_vm().   So I've added the test back.

Coleen