RFR [12] 8213418: Socket/ServerSocket supportedOptions does not work with custom SocketImpl

[Alan Bateman]

On 07/11/2018 15:16, Chris Hegarty wrote:
> Socket and ServerSocket supportedOptions() caches the supported options
> in a static field on the assumption that all implementations support
> the same set of options. This assumption is incorrect.
>
> The cache can be on a per-socket basis ( which has been implemented in
> the webrev ), or maybe even removed completely and just defer to the
> impl. The reason I left the per-socket cache is to avoid creating the
> additional unmodifiable wrapper for every access ( Argh! why didn't we
> specify that SocketImpl::supportedOptions returns an unmodifiable set,
> then there would be no need for this defensive wrapper )
>
> This should to be fixed in advance of JEP 337, which will use a RDMA
> SocketImpl that supports RDMA specific socket options.
>
> http://cr.openjdk.java.net/~chegar/8213418/webrev.00/
Right, the caching, if any, has to be per instance in order to work with 
different SocketImpl implementations. The change drops the 
synchronization and so brings up the question as to whether this method 
is thread safe or not. One simple approach (and there are several) is to 
get rid of the optionsSet flag and change options to be volatile. You 
could use Set.copyOf too.

-Alan