RFR: JDK-8319633: runtime/posixSig/TestPosixSig.java intermittent timeouts on AIX

[Joachim Kern]

Every 1-2 weeks we run into timeouts when running jtreg test runtime/posixSig/TestPosixSig.java on AIX.
The thread stack shows that we are in line 54 of TestPosixSig.java.

The reason is the following: The test registers a new dummy signal handler for SIGILL, without delegating the task to the previous handler in the chain. In case the VM then calls a Java method marked as not-entrant at least on PPC64 a SIGILL is raised. Because this is not handled by the registered handler the SIGILL will happen again and again in an endless recursion.
One solution would be to add a delegation to the hotspot signal handler, which is the previous handler in the chain.

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Commit messages:
 - JDK-8319633

Changes: https://git.openjdk.org/jdk/pull/16797/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=16797&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8319633
  Stats: 20 lines in 1 file changed: 17 ins; 0 del; 3 mod
  Patch: https://git.openjdk.org/jdk/pull/16797.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/16797/head:pull/16797

PR: https://git.openjdk.org/jdk/pull/16797