RFR (S): CR 8005926: (thread) Merge ThreadLocalRandom state into java.lang.Thread

[Chris Hegarty]

Martin, Alan,

OK, I finally got back to this.

I agree that Martins changes should be fine for jdk8, but removing all 
these fields may cause an issue with jdk7. Removing pads, fine. The rnd 
and initialized fields are still applicable in jdk7 ( or 7 will need 
changes to remove their dependency ).

For example, a serialized TLR from jdk8 with Martins changes, 
deserialized with jdk7 would contain no field values, therefore the 
defaults would apply. Calling setSeed on this object would not throw the 
expected UOE.

I think minimally TLR in jdk8 needs to keep initialized, and possibly 
write some reasonable value for rnd.

-Chris.

On 19/02/2013 17:48, Martin Buchholz wrote:
>
>
> On Wed, Jan 16, 2013 at 7:01 AM, Chris Hegarty <chris.hegarty at oracle.com
> <mailto:chris.hegarty at oracle.com>> wrote:
>
>     Thanks to all for the reviews and suggestions here. As you probably
>     seen, I pushed these changes to jdk8/tl earlier today (sorry, I
>     missed Alan as an official reviewer on the changeset.). Consider it
>     an initial version, pending any outcome from this, or other,
>     discussions.
>
>     Also, 8006409: "ThreadLocalRandom should dropping padding fields
>     from its serialized form", has been filed to follow up on the
>     changes required to update the serial form.
>
>     For those watching, I was preferable to push on with these changes (
>     and I apologize if it appeared pushy ), as the Double/Long
>     Adder/Accumulator implementation, Striped64, now has a dependency on
>     this change. It has become unbearable to keep in sync with different
>     version of across different repositories.
>
>
> Taking a look at this, I don't see any reason why we can't simply do
> (while maintaining serialization compatibility):
>
>   diff --git
> a/src/share/classes/java/util/concurrent/ThreadLocalRandom.java
> b/src/share/classes/java/util/concurrent/ThreadLocalRandom.java
> --- a/src/share/classes/java/util/concurrent/ThreadLocalRandom.java
> +++ b/src/share/classes/java/util/concurrent/ThreadLocalRandom.java
> @@ -368,50 +368,6 @@
>       private static final long serialVersionUID = -5851777807851030925L;
>       /**
> -     * @serialField rnd long
> -     * @serialField initialized boolean
> -     * @serialField pad0 long
> -     * @serialField pad1 long
> -     * @serialField pad2 long
> -     * @serialField pad3 long
> -     * @serialField pad4 long
> -     * @serialField pad5 long
> -     * @serialField pad6 long
> -     * @serialField pad7 long
> -     */
> -    private static final ObjectStreamField[] serialPersistentFields = {
> -            new ObjectStreamField("rnd", long.class),
> -            new ObjectStreamField("initialized", boolean.class),
> -            new ObjectStreamField("pad0", long.class),
> -            new ObjectStreamField("pad1", long.class),
> -            new ObjectStreamField("pad2", long.class),
> -            new ObjectStreamField("pad3", long.class),
> -            new ObjectStreamField("pad4", long.class),
> -            new ObjectStreamField("pad5", long.class),
> -            new ObjectStreamField("pad6", long.class),
> -            new ObjectStreamField("pad7", long.class) };
> -
> -    /**
> -     * Saves the {@code ThreadLocalRandom} to a stream (that is,
> serializes it).
> -     */
> -    private void writeObject(java.io.ObjectOutputStream out)
> -        throws java.io.IOException {
> -
> -        java.io.ObjectOutputStream.PutField fields = out.putFields();
> -        fields.put("rnd", 0L);
> -        fields.put("initialized", true);
> -        fields.put("pad0", 0L);
> -        fields.put("pad1", 0L);
> -        fields.put("pad2", 0L);
> -        fields.put("pad3", 0L);
> -        fields.put("pad4", 0L);
> -        fields.put("pad5", 0L);
> -        fields.put("pad6", 0L);
> -        fields.put("pad7", 0L);
> -        out.writeFields();
> -    }
> -
> -    /**
>        * Returns the {@link #current() current} thread's {@code
> ThreadLocalRandom}.
>        */
>       private Object readResolve() {
>