RFR: JDK-8319633: runtime/posixSig/TestPosixSig.java intermittent timeouts on UNIX [v4]

[Joachim Kern]

> Every 1-2 weeks we run into timeouts when running jtreg test runtime/posixSig/TestPosixSig.java on UNIX.
> 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.

Joachim Kern has updated the pull request incrementally with one additional commit since the last revision:

  tried to follow the suggested comments

-------------

Changes:
  - all: https://git.openjdk.org/jdk/pull/16797/files
  - new: https://git.openjdk.org/jdk/pull/16797/files/d6fe9c6c..714c3c56

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=16797&range=03
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=16797&range=02-03

  Stats: 6 lines in 1 file changed: 1 ins; 0 del; 5 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