On Thu, 19 Jan 2023 01:04:39 GMT, Chris Plummer <[email protected]> wrote:
>> src/jdk.jdi/share/classes/com/sun/tools/jdi/VMState.java line 177:
>>
>>> 175: private void removeUnreachableListeners() {
>>> 176: boolean found = false;
>>> 177: while (listenersReferenceQueue.poll() != null) {
>>
>> Hello Chris, I have no prior knowledge of this code, so this is just a
>> casual observation - should this change here be a `if` instead of a `while`?
>> I see that this `removeUnreachableListeners()` gets called whenever a new
>> listener is being added in `addListener(...)`. With the use of `while`, is
>> this intentionally waiting for the GC to kick in and add at least one
>> reference object to this queue?
>
> No, because we have to clear the queue. This code could have been written as:
>
> boolean found = listenersReferenceQueue.poll();
> while (listenersReferenceQueue.poll() != null);
>
> But you are partly right in that `removeUnreachableListeners()` doesn't
> really do anything until after a GC has triggered adding some objects to the
> queue. When there is one, there are probably a bunch, and they'll all get
> handled by the code below the above code. If there are none on the queue,
> then this method doesn't really do anything and has almost no overhead.
Thank you for that explanation Chris. What you state makes sense. I originally
misread that while construct.
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PR: https://git.openjdk.org/jdk/pull/12081
