RFR: JDK-8260485: Simplify and unify handler vectors in Posix signal code [v2]

[Thomas Stuefe]

On Wed, 3 Feb 2021 00:54:23 GMT, David Holmes <dholmes at openjdk.org> wrote:

>> Thomas Stuefe has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains five additional commits since the last revision:
>> 
>>  - Make SavedSignalHandlers use C-heap for its items
>>  - Removed display-replaced-handler-logic
>>  - Feedback David
>>  - Merge
>>  - JDK-8260485-signal-handler-improvements
>
> src/hotspot/os/posix/signals_posix.cpp line 1392:
> 
>> 1390: 
>> 1391: // Print established signal handler for this signal.
>> 1392: // - if this signal handler was installed by us and is chained to a pre-established user handler
> 
> It is not clear to me that this check still remains somewhere.

I removed this check since I did not think it very useful. We have the checking code with Xcheck:jni, which does the same check. 

But I am now reconsidering. If we run without Xcheck, it still is useful. I'll re-add this test.

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PR: https://git.openjdk.java.net/jdk/pull/2251