RFR: JDK-8284874: Add comment to ProcessHandle/OnExitTest to describe zombie problem

Thu Apr 14 09:39:38 UTC 2022

ProcessHandle/OnExitTest is vulnerable to misconfigured systems that do not reap zombies in a timely fashion. [JDK-8284282](https://bugs.openjdk.java.net/browse/JDK-8284282) describes this problem in detail.

Until we figure out a way to fix that (if at all - see comments in JBS), let us have a clarifying comment in the test itself.

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Commit messages:
 - add comment

Changes: https://git.openjdk.java.net/jdk/pull/8240/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=8240&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8284874
  Stats: 17 lines in 1 file changed: 17 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/8240.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/8240/head:pull/8240

PR: https://git.openjdk.java.net/jdk/pull/8240