RFR (XS): CR 8004330: Add missing Unsafe entry points for addAndGet() family (original) (raw)

Doug Lea dl at cs.oswego.edu
Wed Jan 9 11:36:40 UTC 2013

On 01/09/13 06:04, Aleksey Shipilev wrote:

I actually have the question about this. What is the usual pattern for using AtomicLong.VMSUPPORTSLONGCAS? AtomicLong seems to use Unsafe directly without the checks. AtomicLongFieldUpdater does the checks. Something is fishy about this whole thing.

Here's the story: Any implementation of Long-CAS on a machine that does not have any other way to support it is allowed to emulate by a synchronized block on enclosing object. For the AtomicXFieldUpdaters classes, there was, at the time they were introduced, no way to express the object to use, so the checks were done explicitly. I don't think this is even necessary anymore, but doesn't hurt. Further, I'm not sure that JDK8 is even targeted to any machines that require this kind of emulation.

-Doug

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