move `ARef<T>` and `AlwaysRefCounted` to `sync`

[BennoLossin]

ARef<T> and AlwaysRefCounted are currently defined in types.rs which doesn't really fit. Thus move them to sync/aref.rs.

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[Shankari02]

Hello,

I would be interested to work on this issue. Will send a patch to the mailing-list according to the specified instructions.

[Shankari02]

Hello @BennoLossin,

I've moved ARef<T> and AlwaysRefCounted from types.rs to sync/aref.rs as suggested. However, several modules across the kernel tree currently import these types from crate::types.

Would you prefer that I:
Re-export them from types.rs to maintain compatibility, or
Update all call sites to import directly from sync::aref?

Let me know which approach you'd prefer for this patch. Thanks!

[ojeda]

If there are not too many, it may be possible to do it at once early in a kernel cycle. In general, we may need a transition period, i.e. we do one kernel cycle with all existing instances moved, and then early the next kernel cycle we remove the re-export at the same time that we move any new ones that appeared during the last one.

(Side-note: for bigger ones in the future, we may want to leverage Clippy).

[Shankari02]

If there are not too many, it may be possible to do it at once early in a kernel cycle. In general, we may need a transition period, i.e. we do one kernel cycle with all existing instances moved, and then early the next kernel cycle we remove the re-export at the same time that we move any new ones that appeared during the last one.

(Side-note: for bigger ones in the future, we may want to leverage Clippy).

I can see around 29 references. Possibly I'll re-export them from types.rs to aref.rs in this patch and in the next patch, i'll update the call sites to import from sync::aref?

[BennoLossin]

splitting the update patch from the moving patch sounds like a good idea.

I don't think that we need to split the two patches over different cycles. As Miguel said, we can just pick it early in the cycle.

[Shankari02]

Sent a patch