Fwd: RFR: 8181085: Race condition in method resolution may produce spurious NullPointerException

[Andrew Dinn]

Apologies but this RFR is retracted -- the problem only applies to jdk8.

I will be posting a revised RFR to jdk8u.

regards,


Andrew Dinn
-----------
Senior Principal Software Engineer
Red Hat UK Ltd
Registered in England and Wales under Company Registration No. 03798903
Directors: Michael Cunningham, Michael ("Mike") O'Neill, Eric Shander

On 25/05/17 14:16, Andrew Dinn wrote:
> Forwarding this to hotpsot-dev which is probably the more appropriate
> destination.
>
>
> -------- Forwarded Message --------
> Subject: RFR: 8181085: Race condition in method resolution may produce
> spurious NullPointerException
> Date: Thu, 25 May 2017 14:12:53 +0100
> From: Andrew Dinn <adinn at redhat.com>
> To: jdk10-dev <jdk10-dev at openjdk.java.net>
>
> The following webrev fixes a race condition that is present in jdk10 and
> also jdk9 and jdk8. It is caused by a misplaced volatile keyword that
> faild to ensure correct ordering of writes by the compiler. Reviews welcome.
>
>   http://cr.openjdk.java.net/~adinn/8181085/webrev.00/
>
> Backporting:
> This same fix is required in jdk9 and jdk8.
>
> Testing:
> The reproducer posted with the original issue manifests the NPE reliably
> on jdk8. It does not manifest on jdk9/10 but that is only thanks to
> changes introduced into the resolution process in jdk9 which change the
> timing of execution. However, without this fix the out-of-order write
> problem is still present in jdk9/10, as can be seen by eyeballing the
> compiled code for ConstantPoolCacheEntry::set_direct_or_vtable_call.
>
> The patch has been validated on jdk8 by running the reproducer. It stops
> any resulting NPEs.
>
> The code for ConstantPoolCacheEntry::set_direct_or_vtable_call on
> jdk8-10 has been eyeballed to ensure that post-patch the assignments now
> occur in the correct order.
>
> regards,
>
>
> Andrew Dinn
> -----------
> Senior Principal Software Engineer
> Red Hat UK Ltd
> Registered in England and Wales under Company Registration No. 03798903
> Directors: Michael Cunningham, Michael ("Mike") O'Neill, Eric Shander
>
>