RFR: JDK-8303861: Error handling step timeouts should never be blocked by OnError and others [v3]

[Thomas Stuefe]

> Fatal error handling is subject to several timeouts:
> - a global timeout (controlled via ErrorLogTimeout)
> - local error reporting step timeouts.
> 
> The latter aims to "give the JVM a kick" if it gets stuck in one particular place during error reporting. This prevents one error reporting step from hogging all the time allotted to error reporting under ErrorLogTimeout.
> 
> There are three situations where atm we suppress the global error timeout:
> - if the JVM is embedded and the launcher has its abort hook installed. Obviously, that must be allowed to run.
> - if the user specified one or more OnError commands to run, and these did not yet run. These must have a chance to run unmolested.
> - if the user (typically developer) specified ShowMessageBoxOnError, and the error box has not yet been shown
> 
> There is a bug though, that also prevents the step timeout from firing if either condition is true. That is plain wrong.
> 
> In addition to that, the test interval WatcherThread uses to check for timeouts should be decreased. It sits at 1 second, which is too coarse-grained. 
> 
> --------
> 
> Patch:
> - reworks `VMError::check_timeout()` to never block step timeouts
> - adds clarifying comments
> - quadruples timeout check frequency by watcher thread
> - adds regression test for timeout handling with OnError
> - additionally limits timeout per individual error reporting step to 5 seconds. 5 seconds is usually enough to distinguish a slow error reporting step from one that is endlessly hanging. 
> 
> Tested locally on Linux x64.

Thomas Stuefe has updated the pull request incrementally with one additional commit since the last revision:

  feedback roman

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/12936/files
  - new: https://git.openjdk.org/jdk/pull/12936/files/70b9add7..2c21ac35

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=12936&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=12936&range=01-02

  Stats: 6 lines in 1 file changed: 0 ins; 0 del; 6 mod
  Patch: https://git.openjdk.org/jdk/pull/12936.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/12936/head:pull/12936

PR: https://git.openjdk.org/jdk/pull/12936