[jmm-dev] bitwise RMW operators, specifically testAndSetBit/BTS

[Doug Lea]

On 07/18/2016 07:43 AM, Paul Sandoz wrote:

> In terms of the Unsafe Java implementations have i got the following correct (it’s the acquire variant i am unsure of)?
>

These look OK. For ARM/POWER, it's possible to avoid some fences in loops
at assembly level, but that's why they are intrinsics.

>
> Separately, i would like to propose a naming scheme:
>
> - for the read or write method, plain is the default.
>
> - for read-modify-write methods volatile is the default volatile
>    - rename weakCompareAndSet to weakCompareAndSetPlain
>    - rename weakCompareAndSetVolatile to weakCompareAndSet
>    - deprecate (not for removal) Atomic*.weakCompareAndSet, add Atomic*.weakCompareAndSetPlain
>      which leaves the inconsistency of Atomic*.weakCompareAndSetVolatile.
>

Sure. This does seem slightly better.
(And I'm content to continue to take the blame for OKing the naming :-)

> On 07/18/2016 02:27 PM, Andrew Haley wrote:
>> On 18/07/16 12:43, Paul Sandoz wrote:
>>> - for the read or write method, plain is the default.
>>>
>>> - for read-modify-write methods volatile is the default volatile
>>>    - rename weakCompareAndSet to weakCompareAndSetPlain
>>
>> Why "plain"?  Is this the same as C++ "relaxed"?

In this case, yes. But Java-plain is not necessarily always the
same as C++ relaxed, so we've been cautious with namings.

-Doug