RFR: AArch64: 8179954: AArch64: C1 and C2 volatile accesses are not sequentially consistent

[Aleksey Shipilev]

On 05/09/2017 07:18 PM, Andrew Haley wrote:
> In C2 we use LDAR/STLR to handle volatile accesses, but in C1 and the
> interpreter we use separate DMB instructions and relaxed loads. When
> used together, these do not form a sequentially-consistent memory
> ordering. For example, if stores use STLR and loads use LDR;DMB a
> simple Dekker idiom will fail.
> 
> This is extremely hard to test because the loads and stores have to be
> in separately-compiled methods, but it is incorrect, and likely to
> fail in very weakly-ordered implementations.
> 
> Note: this is for JDK 9.
> 
>  http://cr.openjdk.java.net/~aph/8179954/

Makes sense to me.

-Aleksey