RFR: 8288984: Simplification in Shutdown.exit [v2]

[Chris Hegarty]

On Mon, 4 Jul 2022 16:31:22 GMT, Alan Bateman <alanb at openjdk.org> wrote:

>> I reworded with the suggested text in mind. I also added another sentence referencing native signal handlers, which may also initiate shutdown. I think this clarification is important so that it is clear the status code of all invocations from Java may still be ignored. See [2253259](https://github.com/openjdk/jdk/pull/9351/commits/2253259c82b13e7b2186429a80cc42497235b035).
>
> I think the wording in the latest commit (9d972b) is problematic. One reason is that you've changed it to "will run shutdown hooks" but it doesn't run the hooks, it starts them, and so conflicts with the previous paragraph. I also think "That invocation may be initiated via platform specific signal handlers" is confusing here as there is no notion of "signal handler" to reference. There may be scope for text elsewhere, maybe with an implNote for signals such as HUP, but I don't think this is the PR for this. So I think it better to try the wording that David suggested and see if it needs any improvement.

YAO (Yet Another Opinion)!  But I think we're actually converging.

David's wording:
>Invocations of this method are serialized such that only one invocation will actually proceed with the shutdown sequence and terminate the VM with the given status code.

... gives the impression that an invocation of this method WILL terminate the VM with the given status code - which is not actually true, given the potential for signals. This is already alluded to in `Runtime::addShutdownHook`. I agree that this could be resolved separately, but we should _allow_ for it.
 
The original wording:
> If this method is invoked after all shutdown hooks have already been run ... 

... seems quite clever (and allows for signals). Maybe we could:
> If this method is invoked after shutdown hooks have already been started it will block indefinitely. If this method is invoked from a shutdown hook the system will deadlock.

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

PR: https://git.openjdk.org/jdk/pull/9351