RFR 8199435 : Unsafe publication of java.util.Properties.map

[Claes Redestad]

I'd suggest something simple like this to ensure correctness, while 
keeping the number of volatile reads to a minimum:

http://cr.openjdk.java.net/~redestad/8199435.00/

Then file a follow-up RFE to investigate if we can make these fields 
non-volatile, e.g. using careful fencing as suggested
by Peter.

/Claes

On 2018-06-18 15:27, Claes Redestad wrote:
>
>
> On 2018-06-18 13:06, Peter Levart wrote:
>>> Adding a volatile read on every read through Properties is likely to 
>>> have some performance impact,
>>
>> On non-Intel architectures in particular. On intel it would just 
>> inhibit some JIT optimizations like hoisting the read of field out of 
>> loop... 
>
> Right, and coincidentally those platforms are where I'd expect the 
> current implementation to cause bugs (I've not been able to provoke
> any real error on my Intel-based workstations).
>
> I'd be surprised if we'd be much slower than pre-8029891 using 
> volatiles (volatile read vs synchronized - even with biased locking),
> and we'd still retain the scalability benefits of 8029891.
>
> Ignore my remarks about clone - I'm just back from vacation and have 
> apparently forgotten how cloning works. :-)
>
> /Claes