RFR: 8259937: guarantee(loc != NULL) failed: missing saved register with native invoker [v4]

[Andrew Dinn]

On Wed, 24 Feb 2021 20:57:10 GMT, Jorn Vernee <jvernee at openjdk.org> wrote:

>> Roland Westrelin has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Revert "test & debug"
>>   
>>   This reverts commit cb9dd24c9fcccc6997e9fca874e2860f966b9576.
>
> Thanks for addressing the comments! Looks good.

@JornVernee I'm not clear that your response addresses my point. I'm concerned that a thread stack dump reported by serviceability code may contain an extra frame for the stub call. This could occur while the Java thread is still in native and it could also include the case wher the native call re-enters into Java i.e. the extra frame could appear at the top of the stack dump or interleaved between Java method frames.

I don't see how that problem is mitigated by your suggestion that this only relates to Panama API use. Code which consumes any such stack dump (incluing 3rd party code) that might be affected by the presence of this extra frame will not care (or even be aware) that the native callout is a Panama call.

Anyway, since no one from the serviceability team has noted this as a potential problem I'm ok to see the patch proceed.

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PR: https://git.openjdk.java.net/jdk/pull/2528