RFR: 8322784: JFXPanel calls InputMethodRequests on wrong thread [v2]

[Andy Goryachev]

On Mon, 22 Jan 2024 20:52:56 GMT, Martin Fox <mfox at openjdk.org> wrote:

>> I might be wrong, but array would need to store its size (an int, 8 bytes on 64 bit machines) in addition to the pointers themselves, while AtomicReference needs just the pointer.
>> Plus, its semantics is much cleaner.
>
> Again, thread-safety isn't an issue here. Even if the OS were to invoke the IM methods on different threads (which is a terrifying thought) these adapters are created on a per-call basis so each thread would get its own instance. This also means those extra eight bytes are transitory.
> 
> If there's an established JavaFX pattern of using AtomicReference instead of an array I will gladly make the changes. But this does require manual testing (I still haven't figured out how to automate this) so I'm reluctant to do this based on personal style preferences.

Here is more info [0].

We **are** dealing with multiple threads.

I've seen weird cases where modifying memory from different threads without explicit synchronization resulted in subtle bugs - we don't know all the details of cache coherence [1] implementation in multi-core systems, so I would strongly suggest to use AtomicReference.

[0] https://stackoverflow.com/questions/70381029/java-atomincinteger-vs-one-element-array-for-streams

[1] https://en.wikipedia.org/wiki/Cache_coherence

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

PR Review Comment: https://git.openjdk.org/jfx/pull/1337#discussion_r1462422366