RFR: 8298853: JvmtiVTMSTransitionDisabler should support disabling one virtual thread transitions [v2]

[Serguei Spitsyn]

On Tue, 20 Dec 2022 04:49:46 GMT, David Holmes <dholmes at openjdk.org> wrote:

>> This update just follows the common pattern which was introduced about two years ago. At the moment I do not remember the exact reason. This code needs to wait for the counter to become zero and to use `ThreadBlockInVM` which can reach a safepoint in the destructor. Can we lock with a safepoint check in this case? Or we should get rid of the `ThreadBlockInVM` then?
>> I'll check if this can be fixed.
>
> This can be a separate RFE if the reason for it being a nosafepoint lock no longer holds. It would be cleaner to use a normal safepoint checking lock than to artificially make the thread safepoint-safe before using it.

Agreed. I was thinking about a separate RFE. I started seeing some failures in the S/R related tests with the removed `ThreadBlockInVM` and `_no_safepoint_check_flag`. Need to investigated why. Otherwise, it seems to be working well.

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PR: https://git.openjdk.org/jdk/pull/11690