Should AbstractInterruptibleChannel.close() still use a synchronized block?

[Mark Rotteveel]

Prompted by this Stack Overflow question 
[https://stackoverflow.com/q/77315894/466862], I'm wondering if the use 
of a synchronized block in AbstractInterruptibleChannel.close() as-of 
Java 21 is correct, and shouldn't be replaced with a ReentrantLock or 
something else.

As shown in the question, closing of a channel derived from 
AbstractInterruptibleChannel can cause pinning of virtual threads.

Mark
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Mark Rotteveel