On 23/02/15 14:08, Vitaly Davidovich wrote:
Likewise, seems fine.
Thanks Vitaly.
By the way, is there a reason not to call freeze() right before returning obj? Is there something special about the place it's invoked at now?
Probably not. The freeze should probably happen before the ObjectInputValidation callback, as this justs opens another opportunity for early publication of the object, but probably after the handle update and check.
Also, hasFinal field can be final, unless I missed some context in the webrev.
It could be, but I omitted it as it requires a pesky explicit assignment of false in the case where there are not final fields!
For completeness, updated webrev in-place, which I intend to push, unless there are further comments:
http://cr.openjdk.java.net/~chegar/deserialFence/webrev.02/webrev/ -Chris.
sent from my phone On Feb 23, 2015 7:30 AM, "David Holmes" <david.hol...@oracle.com <mailto:david.hol...@oracle.com>> wrote: 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/ <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.
