RFR: 8293839: Documentation memory consistency effects of runLater

[Kevin Rushforth]

On Wed, 17 Aug 2022 07:21:43 GMT, Jens Lidestrom <duke at openjdk.org> wrote:

> Prior to this change it was not clear from the documentation if callers of Platform#runLater must perform
> any synchronisation to have writes of the calling thread be visible in the JavaFX Application
> Thread. It is important to document either if callers can rely on runLater to do such synchronisation
> internally, or to document is users CAN NOT rely on runLater for this.
> 
> This change documents that actions in a thread prior to submitting a runnable to
> Platform#runLater happen-before actions performed by the runnable in the JavaFX
> Application Thread.
> 
> runLater inherits the memory consistency effects of InvokeLaterDispatcher in most cases. 
> InvokeLaterDispatcher uses BlockingDeque internally. This change documents this
> in the same way as it is documented by BlockingDeque.
> 
> Other implementations of runLater should have similar memory consistency effects.

This is now ready to review, so I'll take a look. One thing to note, though, is that the `/summary` is an optional extra line of information that gets recorded into a commit. Most of the time it is unused, but if it is used, it should not be a copy of the title. I recommend removing it with `/summary` in a comment by itself with no other text.

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PR: https://git.openjdk.org/jfx/pull/872