RFR: 8252324: Signal related code should be shared among POSIX platforms

[Martin Doerr]

On Wed, 23 Sep 2020 19:12:46 GMT, Gerard Ziemski <gziemski at openjdk.org> wrote:

>>> _Mailing list message from [Doerr, Martin](mailto:martin.doerr at sap.com) on
>>> [hotspot-runtime-dev](mailto:hotspot-runtime-dev at openjdk.java.net):_
>>> Hi Gerard,
>>> 
>>> sorry for the long delay. It took time to get our nightly tests working again on AIX.
>>> I have seen an issue, but it may be unrelated to your change. We'll retest it.
>> 
>> I will take another look at AIX changes to see if I missed something.
>> 
>> 
>>> Note that there's still unused code left in os_aix.cpp (see below).
>>> Thanks again for taking care of AIX. I appreciate having more shared POSIX code.
>> 
>> Thank you for the diff, I'll use it and update the webrev.
>
>> > _Mailing list message from [Doerr, Martin](mailto:martin.doerr at sap.com) on
>> > [hotspot-runtime-dev](mailto:hotspot-runtime-dev at openjdk.java.net):_ Hi Gerard,
>> > sorry for the long delay. It took time to get our nightly tests working again on AIX.
>> > I have seen an issue, but it may be unrelated to your change. We'll retest it.
>> 
>> I will take another look at AIX changes to see if I missed something.
> 
> I took another look at the changes and I have concerns over the following methods:
> 
> PosixSignals::SR_handler
> PosixSignals::do_suspend
> PosixSignals::do_resume
> 
> They seem to differ substantially in parts from the other POSIX platforms. In my early webrevs I have accounted for
> those changes using "#if defined(AIX)", but during pre-reviews you asked me to revert to the common POSIX code.
> Can you please take a look again and tell me if you are OK with the following SA related changes:
> 
> - using POSIX semaphores
> - using the common POSIX code
> 
> I will upload, what I think (based only on the code diffs between the platforms as I lack AIX platform understanding)
> the AIX platform needs here.

I believe the reason for not using POSIX semaphores was that it is not supported on as400 PASE which we don't support
in OpenJDK. I'm not aware of any problems when using this common POSIX code on AIX 7.2. Is SA supported on AIX? That
would be new to me. But I'm not an expert for these topics. I hope that Thomas can find some time to take a look.

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PR: https://git.openjdk.java.net/jdk/pull/157