RFR: 8271471: [IR Framework] Rare occurrence of "<!-- safepoint while printing -->" in PrintIdeal/PrintOptoAssembly can let tests fail

[David Holmes]

On Thu, 29 Jul 2021 12:25:27 GMT, Christian Hagedorn <chagedorn at openjdk.org> wrote:

> A test VM used by the IR framework sometimes prints `` in the middle of emitting a `PrintIdeal` or `PrintOptoAssembly` output which could lead to IR matching failures:
> https://github.com/openjdk/jdk/blob/489e5fd12a37a45f4f5ea64b05f85c6f99f70811/src/hotspot/share/utilities/ostream.cpp#L918-L927
> 
> I thought about just bailing out of IR matching if this string is found after a failure but this issue also affects internal framework tests (I observed one case locally where this happened in the test `TestIRMatching`, letting it fail).
> 
> Handling `` makes things more complicated for the IR framework tests. I'm not sure about the value of printing this message in the first place. But if nobody objects, I suggest to either remove it or at least guard it with `Verbose`, for example. I went with the latter solution in this PR.
> 
> Thanks,
> Christian

I think the expectation is that a safepoint whilst printing and holding the tty lock should be a very rare thing, possibly indicative of an error, and so something we want to know about. If this is hidden by Verbose then it will effectively always be hidden and we won't spot this.

Do you understand why this is getting printed in this context, and that it doesn't indicate a problem?

Thanks,
David

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PR: https://git.openjdk.java.net/jdk/pull/4932