RFR: 8203028: Simplify reference processing in light of JDK-8175797 (original) (raw)

mandy chung mandy.chung at oracle.com
Tue May 22 22:09:36 UTC 2018

Hi Kim,

Thanks for doing this work and rewriting the comments.  It's great to see this simplification.  It looks good in general.  I have a couple of personal preferences if you are okay to update them.

I like to keep the existing indentation of the description of different states (line 50-75) that makes them easy to read.

"normal reference"  - I suggest to change it to "soft, weak, or phantom reference".   FinalReference is also a Reference object and it's an implementation class that supports finalization.   Making it explicit would avoid confusion.

86 * FinalReference (which exists to support finalization, which was 87 * deprecated in JDK 9) differs from normal references

I suggest to drop "which was deprecated in JDK 9" since @Deprecated is in the javadoc and no implication to the implementation.

Thanks for adding the comment of the possible transitions.   I was tempted to make an ascii flow chart.   State change due to the API makes it harder to draw.   This is my first snap but it's not yet in a satisfying state.   I think this is clearer than the text description.  What do you think?  If we like this, I can clean that up and send you a revised version.

114 * -> inactive/unregistered - GC, clear, enqueue

Under what circumstance does GC make a reference from active/unregistered -> inactive/unregistered?

Mandy

On 5/20/18 8:12 AM, Kim Barrett wrote:

On May 15, 2018, at 12:09 AM, Kim Barrett <kim.barrett at oracle.com> wrote: New webrev, rebased to include JDK-8201491: http://cr.openjdk.java.net/~kbarrett/8203028/open.01/

New webrevs with above changes: full: http://cr.openjdk.java.net/~kbarrett/8203028/open.02/ incr: http://cr.openjdk.java.net/~kbarrett/8203028/open.02.inc/ Following up on a suggestion from Mark Reinhold in the discussion of JDK-8203327 on the core-libs list, I’ve added the following comment to the Reference.queue field. diff -r 98982cddbac0 -r 2429129c4d48 src/java.base/share/classes/java/lang/ref/Reference.java --- a/src/java.base/share/classes/java/lang/ref/Reference.java Mon May 14 18:01:36 2018 -0400 +++ b/src/java.base/share/classes/java/lang/ref/Reference.java Sun May 20 11:06:48 2018 -0400 @@ -131,6 +131,14 @@ private T referent; /* Treated specially by GC */ + /* The queue this reference gets enqueued to by GC notification or by + * calling enqueue(). + * + * When registered: the queue with which this reference is registered. + * enqueued: ReferenceQueue.ENQUEUE + * dequeued: ReferenceQueue.NULL + * unregistered: ReferenceQueue.NULL + */ volatile ReferenceQueue<? super T> queue; /* The link in a ReferenceQueue's list of Reference objects.

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