RFR [9]: default Serialization should issue a fence after reconstructing an Object with final fields

[David Holmes]

Hi Chris,

On 23/02/2015 9:01 PM, Chris Hegarty wrote:
> Peter, David, Vitaly,
>
> Can you please take a look at the latest version of this change:
>
>    http://cr.openjdk.java.net/~chegar/deserialFence/webrev.02/webrev/

It seems reasonable but I don't have a clear picture of the connection 
between readObject and readSerialData.

David

> On 20/02/15 15:09, Peter Levart wrote:
>> ...
>> This looks good now. But I wonder if issuing fences after nested calls
>> to readObject() makes much sense. If cycles are present in a subgraph
>> deserialized by nested call to readObject(), a field pointing back to an
>> object not part of the subgraph stream will point to the object that
>> will not be fully initialized yet, so nested calls to readObject()
>> should not be expected to return a reference to a fully constructed
>> subgraph anyway. Only top-level call is guaranteed to return a fully
>> constructed graph.
>
> Right. I was never convinced of this myself either. Removed. Unnecessary
> complication.
>
>> If you optimize this and only issue one fence for top-level call to
>> readObject(), tracking of 'requiresFence' (I would call it
>> requiresFreeze to be in line with JMM terminology - the fence is just a
>
> 'requiresFreeze' is better. Updated
>
>> way to achieve freeze) can also be micro-optimized. You currently do it
>> like this:
>>
>> 1900             requiresFence |= slotDesc.hasFinalField();
>>
>> which is a shortcut for:
>>
>> requiresFence = requiresFence | slotDesc.hasFinalField();
>>
>> ...which means that the field is overwritten multiple times
>> unnecessarily and slotDesc.hasFinalField() is called every time. You can
>> write the same logic as:
>>
>> if (!requiresFence && slotDesc.hasFinalField()) {
>>      requiresFence = true;
>> }
>
> ... and it is more readable. Updated.
>
>> There will be at most one write to the field and potentially less calls
>> to slotDesc.hasFinalField().
>
> -Chris.