[waddlesplash]

> The Alpha doesn't promise that there's any coherent ordering at all unless you've imposed one

Yes. But why did you bring this up in this thread about API usage? It's the implementation's problem to make this work out. "Add()" should be the equivalent of a full memory barrier (at least for the condition variable's memory) no matter how that happens internally.

> This price isn't unique to Haiku, but the choice to pay it (almost) everywhere is, at least in terms of operating systems people would be using today.

Haiku is, in many ways, poorly optimized when compared on such details with Linux or FreeBSD, all the developers know this fact, and we make no secret of it. If this was your entire point in the first place, why not just say so?

By the way, as far as I can tell, OpenBSD's kernel atomics (sys/atomic.h) do not have different versions for different memory orderings; in fact they use the older-style GCC builtins and not the C++11-style ones, so they are also using sequential consistency everywhere they use atomics. Is OpenBSD not a "modern operating system people would be using today"?

[tialaramex]

I guess, ultimately if the argument is we don't care about performance or capability then, you know, fine, although if you don't care it's weird to do two rewrites focused on performance and write a blog post to highlight the work.

AIUI OpenBSD doesn't lean exclusively on those primitives, you might notice for example it has futexes these days. On the other hand I also don't know anybody who runs OpenBSD.