RFR: 8287281: adjust guarantee in Handshake::execute for the case of target thread being current

[Robbin Ehn]

On Thu, 2 Jun 2022 13:47:23 GMT, Johan Sjölén <duke at openjdk.java.net> wrote:

> Please review this PR for fixing JDK-8287281.
> 
> I chose a different solution than the one suggested. Looking at all callers of `Handshake::execute`, it seems that only one depends on `target == current`. The rest special case that by calling `is_handshake_safe_for` and `do_thread` directly.  I converted the only instance of `Handshake::execute` with `target == current` to just directly call `do_thread`.
> 
> Furthermore we now explicitly check for this case in `Handshake::execute` with an assert and document that this should not be done.
> 
> Finally:  Should `VirtualThreadGetThreadClosure` and its `do_thread()` body be inlined instead? We can do this in this PR, imho, but I'm hoping to get some input on this.
> 
> 
> Currently running tier1-5 to check if I'm missing something.

I agree, thanks for fixing.

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Marked as reviewed by rehn (Reviewer).

PR: https://git.openjdk.java.net/jdk/pull/8992