RFR: 8291650: Add delay to ClassUnloadEventTest before exiting to give time for JVM to send all events before VMDeath

[Chris Plummer]

On Mon, 1 Aug 2022 21:25:09 GMT, Serguei Spitsyn <sspitsyn at openjdk.org> wrote:

> This looks okay to me.
> However, it can be still unreliable.
> Is there a way to check-wait for the expected class unload events?

The debuggee would need to block until the debugger says it got all the events. Currently the debugger just runs until it gets a VMDeathEvent, then it checks if got the expected ClassUnloadEvents. So it would instead have to wait until it got all the expected ClassUnloadEvents (and time out eventually if not). It would also need to communicate with the debuggee. I don't think any of com/sun/jdi tests currently do this. Possibly we could setup a breakpoint in the debuggee after doing the GC, and have the debugger not resume it until after it gets all the expected events. I just felt doing a short sleep was so much easier, especially given that we aren't 100% sure the early VMDeathEvent is the cause of this issue. At the very least it would be nice to see if this simple solution is fixing the problem.

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PR: https://git.openjdk.org/jdk/pull/9708