Reference.reachabilityFence

[Vitaly Davidovich]

It's requesting the runtime to extend the lifetime of an object that would
otherwise be considered dead.  It's true that no heavy lifting happens
behind the scenes, unlike gc or finalization, but that's not the important
part in my opinion.

On Tue, Nov 24, 2015 at 8:14 AM, David Holmes <david.holmes at oracle.com>
wrote:

> On 24/11/2015 11:00 PM, Vitaly Davidovich wrote:
>
>> One can look at reachabilityFence in same light as requesting gc or
>> finalization, both of which live in Runtime.
>>
>
> I don't quite see how they are "in the same light". Both of those are
> requests for specific system services to be executed (and convenience
> wrappers are provided in the System class). reachabilityFence() isn't
> requesting any kind of service.
>
> But each to their own.
>
> David
>
> sent from my phone
>>
>> On Nov 24, 2015 7:54 AM, "David Holmes" <david.holmes at oracle.com
>> <mailto:david.holmes at oracle.com>> wrote:
>>
>>     On 24/11/2015 7:32 PM, Paul Sandoz wrote:
>>
>>
>>             On 24 Nov 2015, at 01:31, mark.reinhold at oracle.com
>>             <mailto:mark.reinhold at oracle.com> wrote:
>>
>>             2015/11/23 8:38 -0800, paul.sandoz at oracle.com
>>             <mailto:paul.sandoz at oracle.com>:
>>
>>
>>                 Please review the addition of
>>                 Reference.reachabilityFence contributed
>>                 by Aleksey, Doug and myself:
>>
>>
>> http://cr.openjdk.java.net/~psandoz/jdk9/JDK-8133348-reachability-fence-jdk/webrev/
>>
>> http://cr.openjdk.java.net/~psandoz/jdk9/JDK-8133348-reachability-fence-hotspot/webrev/
>>
>>
>>             This seems eminently reasonable, but why does it belong in the
>>             java.lang.ref.Reference class?  It has nothing (directly) to
>> do
>>             with reference objects.
>>
>>             java.lang.Runtime, perhaps?
>>
>>
>>         Out of all the places i thought Reference was the least
>>         indirect. The method documentation refers to the notion of
>>         "strongly reachable” in the j.l.ref package doc (I should update
>>         to link directly to that). In effect it’s an operation on
>>         potential referents that relates to reachability, garbage
>>         collection and finalization.
>>
>>         A further weaker argument is Reference is not commonly used thus
>>         there may be less chance of this method being misused.
>>
>>         I do prefer the current location, but i don’t strongly object to
>>         moving it to Runtime.
>>
>>
>>     As all Runtime methods are instance methods the usage here would be
>>     a bit awkward. Personally I thought reference was a very suitable
>>     location for a reachability-related method.
>>
>>     Cheers,
>>     David
>>
>>         Paul.
>>
>>
>>
>>
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