RFR: 8288324: Loom: Uninitialized JvmtiEnvs in VM_Virtual* ops

[Alan Bateman]

On Mon, 13 Jun 2022 18:14:56 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

> SonarCloud reports a few uninitialized fields in new VM_Virtual* ops. Those fields are used, and therefore this is a serious bug. These ops seem to be used only from a few corner cases, which is probably why this was never actually found in testing.
> 
> Additional testing:
>  - [x] Linux x86_64 fastdebug, `jdk_loom hotspot_loom`
>  - [x] Linux x86_64 fastdebug, `serviceability/jvmti`

@sspitsyn @lmesnik If I read this correctly then this calling JVMTI GetFrameCount or GetStackTrace with a jthread to a virtual thread that is not mounted. I'm surprised this wasn't caught by any tests. Should we add tests for these cases?

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PR: https://git.openjdk.org/jdk19/pull/10