RFR: 8253742: POSIX signal code cleanup

[Thomas Stuefe]

On Tue, 3 Nov 2020 09:42:19 GMT, David Holmes <dholmes at openjdk.org> wrote:

> I hadn't realized that JVM_handle_XXX_signal defined a per-platform "public" entry point to allow external callers of the signal handling function in conjunction with -XX:+AllowUserSignalHandlers. We need to keep these but they can each call JVM_handle_posix_signal as their implementation.

We should disentangle https://bugs.openjdk.java.net/browse/JDK-8255711 and this patch, https://bugs.openjdk.java.net/browse/JDK-8253742.

I started by giving my patch a less generic name ("Fix and unify hotspot signal handlers"). I propose to do the same with this patch, or even split this patch into two smaller parts, since it does two things:
- unify diagnostic printing code
- unify SR handler setup

As I wrote, I'd prefer to keep changes to JVM_xxx and javaSignalHandler out of this patch completely. I have to change those functions since the point of my patch is signal handler unification. 

In turn, I will keep my hands off any other code in signals_posix.xxx to decrease chances of conflict with this patch.

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PR: https://git.openjdk.java.net/jdk/pull/636