How could self link help GC?

[Robert Lu]

Hi, Damon.

But once dequeued, old node is dead object. The pointer(h.next) from dead
object to alive/dead object makes no difference to GC.
So I thinks h.next=h is meaningless.

And, why isn't it h.next=null ?


On Mon, Jun 22, 2020 at 12:18 AM Damon Hart-Davis <dhd at exnet.com> wrote:

> By avoiding spurious pointers to h.next keeping the ’next’ item alive
> longer than necessary.
>
> Rgds
>
> Damon
>
> On 21 Jun 2020, at 12:59, Robert Lu <robberphex at gmail.com> wrote:
>
> Hi,
> On java.util.concurrent.LinkedBlockingQueue#dequeue
> https://github.com/openjdk/jdk/blob/master/src/java.base/share/classes/java/util/concurrent/LinkedBlockingQueue.java#L217
> :
>
> private E dequeue() {
>     // assert takeLock.isHeldByCurrentThread();
>     // assert head.item == null;
>     Node<E> h = head;
>     Node<E> first = h.next;
>     h.next = h; // help GC
>     head = first;
>     E x = first.item;
>     first.item = null;
>     return x;
> }
>
> Why does h.next = h help GC?
>
> --
> Robert Lu <robberphex at gmail.com>
> About me: https://www.robberphex.com/about-me
>
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>
>

-- 
Robert Lu <robberphex at gmail.com>
About me: https://www.robberphex.com/about-me
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