RFR: JDK-8313656: assert(!JvmtiExport::can_support_virtual_threads()) with -XX:-DoJVMTIVirtualThreadTransitions

[Leonid Mesnik]

On Thu, 10 Aug 2023 01:45:47 GMT, Alex Menkov <amenkov at openjdk.org> wrote:

> The change fixes several issues with capability management:
> - handling can_support_virtual_threads capability. JvmtiExport::can_support_virtual_threads() should be set to true if we have one or more agent with can_support_virtual_threads capability;
> - JvmtiManageCapabilities (used by GetPotentialCapabilities/AddCapabilities/RelinquishCapabilities/GetCapabilities) is not thread safe;
> - SuspendAllVirtualThreads and ResumeAllVirtualThreads should check capability on the caller agent (and not JvmtiExport::can_support_virtual_threads()).
> 
> Testing: tier1..5

Marked as reviewed by lmesnik (Reviewer).

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PR Review: https://git.openjdk.org/jdk/pull/15219#pullrequestreview-1603587986