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

[Vitaly Davidovich]

In addition to Peter's comment, full fence seems unnecessarily strong and
will cause performance issues (especially if the fence is per object in the
graph).  A storeFence should be sufficient here, no?

sent from my phone
On Feb 19, 2015 11:32 AM, "Chris Hegarty" <chris.hegarty at oracle.com> wrote:

> Additional note ( forgotten from original mail):
>
> The fence is needed for "final-freeze" is a one-off barrier at the end of
> deserialization, similar that of constructors . Under normal circumstances
> the object being deserialized is not visible until deserialization
> completes, so you don't need a "freeze" until deserialization completes.
>
> -Chris.
>
> On 19 Feb 2015, at 16:25, Chris Hegarty <chris.hegarty at oracle.com> wrote:
>
> > A number of years ago there was a proposal to use Unsafe.put*Volatile
> methods to set final fields during default deserialisation [1][2], but it
> never made it due to concerns about the potential negative impact of the
> additional fences. Now we have a, private, fences API in the platform, I
> think it is time to revisit this.
> >
> > Webrev:
> >  http://cr.openjdk.java.net/~chegar/deserialFence/webrev.00/webrev/
> >
> > Note:
> >  - Section 17.5.3 in the JLS [3], “Freezes of a final field occur both
> >    at the end of the constructor in which the final field is set, and
> >    immediately after each modification of a final field via reflection
> >    or other special mechanism.” I believe this is a consequence of
> >    the way in which setting of final fields is supported in the public
> >    API, Field.setAccessible(), ( as defined by JSR 133 ) and should
> >    not restrict an implementation from using a more performant
> >    means, as is suggested here.  The statement in the JLS should
> >    be revisited.
> >
> > - Default Serialization already has a dependency on Unsafe, and
> >   I don’t see this additional dependency as making that any worse.
> >
> > - Open question, should we include volatile fields as well as final?
> >
> > - The changes in the webrev will issue a fence even if custom
> >   deserialization is performed. I think this is ok, as it will be more
> >   consuming to try to determine if a custom readObject set a final
> >   through reflection, or not.
> >
> > -Chris.
> >
> > [1] https://bugs.openjdk.java.net/browse/JDK-6647361
> > [2]
> http://mail.openjdk.java.net/pipermail/core-libs-dev/2010-November/005292.html
> >
> http://mail.openjdk.java.net/pipermail/core-libs-dev/2010-December/005456.html
> > [3]
> http://docs.oracle.com/javase/specs/jls/se8/html/jls-17.html#jls-17.5.3
>
>