RFR(XXS): 8165018: Missing memory barrier for PPC64 in Unsafe_GetObjectVolatile

David Holmes david.holmes at oracle.com
Fri Sep 2 05:03:39 UTC 2016


Hi Martin,

Adding GC folk

On 30/08/2016 8:51 PM, Doerr, Martin wrote:
> Hi,
>
> we found that a memory barrier for PPC64 is missing in the current Unsafe implementation. get_volatile already contains the memory barrier for "support_IRIW_for_not_multiple_copy_atomic_cpu". The same is needed in Unsafe_GetObjectVolatile.
>
> Here's my webrev:
> http://cr.openjdk.java.net/~mdoerr/8165018_UnsafePPC64/webrev.00/

That looks fine to me.

> And while looking at it I wonder why Unsafe_GetObjectVolatile does not contain a G1 barrier like Unsafe_GetObject. Is it not possible to use the Volatile version to access the referent field of a Reference?

That looks like a bug to me. :)

> Please review. As it is shared code, I will need a sponsor, please.

I can sponsor.

Thanks,
David

> Best regards,
> Martin
>


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