Consider graduating std::unstable::{sync,atomics} to std::sync

[alexcrichton]

The utilities provided inside of std::unstable::{sync,atomics} are quite useful for writing concurrent code. It would be nice to polish off these interfaces and move them outside of the unstable module.

[emberian]

I think this is blocking on #9758

[alexcrichton]

UnsafeArc is correct as-implemented, that issue is just referring to putting unsafe_no_drop_flag on the struct causes problems. I do not think that that issue blocks this.

[thestinger]

It's correct as-implemented but I'm not sure supporting unwrapping as it does it is a good idea. It seems like it would make a lot more sense to just use Arc<Option<T>>.

This is a lot simpler, and can use faster atomic ordering requirements:

https://github.com/thestinger/rust-core/blob/master/core/arc.rs

[brson]

I also believe that UnsafeArc should not support unwrapping.

[brson]

And agree that these should not be in the unstable module (which should be dismantled in favor of attributes anyway).

[brson]

A lot of the stuff in sync though worries me - it's just misc stuff, and some of it is not appropriate for general use. LittleLock and Exclusive use native mutexes.

[brson]

LittleLock is not the right name for something we want to be part of the public API, and both it and Exclusive are conflated with condvars.

[alexcrichton]

I am currently doing this in a local branch, but it may take some time to land.

[alexcrichton]

I'm leaving everything related to a mutex in unstable for now.

[alexcrichton]

This has been done.

[alexcrichton]

Or at least done to the degree that it should be done at this time.