RFR: 8253064: monitor list simplifications and getting rid of TSM [v5]

[Daniel D.Daugherty]

On Tue, 10 Nov 2020 15:02:31 GMT, Daniel D. Daugherty <dcubed at openjdk.org> wrote:

>> I'd rather see ThreadBlockInVM as the convention of allowing the thread to block if a safepoint is requested.  The calls like process_if_requested are becoming alphabet soup and keep changing, so having TBIVM is better in my opinion.
>> That said, this is a strange usage.  This code appears three times.  It should be a function like allow_safepoint_block(LogStream* ls, timer), with some comment above.  Then it's clear that it's checking for a safepoint in a loop that could take a long time and the logging is ancillary.
>
> I previously looked at refactoring the three locations where
> `ThreadBlockInVM` is used. The problem with the refactoring
> is that the log messages and the parameters have some
> differences and some commonalities. Each of these logging
> sites is trying to communicate some local context that is
> unique to that call site along with some global context that
> might have changed from call site to call site.
> 
> I'll take another look at refactoring shortly and will let you
> know what I come up with.

I refactored common ThreadBlockInVM code block into ObjectSynchronizer::chk_for_block_req().
Please let me know if you're okay with it.

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PR: https://git.openjdk.java.net/jdk/pull/642