DIP 1024---Shared Atomics---Community Review Round 2

[Timon Gehr]

On 27.10.19 13:20, Mike Parker wrote:
> This is the feedback thread for the second round of Community Review for 
> DIP 1024, "Shared Atomics":
> 
> https://github.com/dlang/DIPs/blob/0093abce72fa803b9e4067db500171c634daa4a9/DIPs/DIP1024.md 
> 
> 
> All review-related feedback on and discussion of the DIP should occur in 
> this thread. The review period will end at 11:59 PM ET on November 10, 
> or when I make a post declaring it complete.
> 
> At the end of Round 2, if further review is deemed necessary, the DIP 
> will be scheduled for another round of Community Review. Otherwise, it 
> will be queued for the Final Review and Formal Assessment.
> 
> Anyone intending to post feedback in this thread is expected to be 
> familiar with the reviewer guidelines:
> 
> https://github.com/dlang/DIPs/blob/master/docs/guidelines-reviewers.md
> 
> *Please stay on topic!*
> 
> Thanks in advance to all who participate.

Looks good, except for this sentence:

"Atomic reads perform an acquire operation, writes perform a release 
operation, and read-modify-write performs an acquire, then a 
modification, and then a release. The result is sequentially consistent 
ordering, and each thread observes the same order of operations (total 
order)."

While atomics that act like this already provide some useful guarantees, 
this is not enough to ensure sequential consistency for more than two 
threads. This post explains it well: https://stackoverflow.com/a/14864466

Probably the sentence can just be dropped from the DIP, as it does not 
actually describe a language change, and core.atomic is more general 
than this anyway.