Atomic::add(jlong) broken?

[David Holmes]

On 3/02/2016 6:55 AM, Roman Kennke wrote:
> Hello,
>
> I believe Atomic::add(jlong) is broken. The comment above it says:
>
>    // Atomically add to a location, return updated value
>
> Except in atomic.cpp, add(jlong) returns the old value.

Yes that seems broken.

> It causes quite some headscratching on my side :-)
>
> Fixing this seems easy. I am wonder if any code uses this though, maybe
> it should be removed altogether?

It was added here:

http://hg.openjdk.java.net/jdk8/jdk8/hotspot//rev/2a241e764894

for the GC log file rotation code back in 2011. But then removed here:

http://hg.openjdk.java.net/jdk8/jdk8/hotspot/rev/0598674c0056

because it was unnecessary and because of the missing Atomic:load(jlong) 
support it required.

I think it can be deleted now and probably should be.

> On the other hand, the implementation there uses a CAS-based loop. I
> think an easier fix would be to cast to size_t or intptr_t and use the
> atomic impl of that.
>
> What do you think?

Delete it.

Thanks,
David

> Roman
>