Protecting multiple objects with one lock

[mahkoh]

I have the following requirements:

1. I have multiple objects connected via Arc and interior mutability.
2. These objects contain mutable data.
3. I want all of that data to be protected by a single lock.
4. It is ok if the lock only hands out immutable references as long as it maps Send to Sync like ReentrantLock. I can then use cheap, non-Sync interior mutability for the actual mutations.

I've implemented this here on top of the parking_lot RawMutex: https://docs.rs/shared-lock

Do you think it makes sense to support this pattern in parking_lot directly?

[qti3e]

You might find this pattern interesting: https://github.com/torvalds/linux/blob/master/rust/kernel/sync/locked_by.rs

[mahkoh]

It's similar but not the same. Both implementations map Send to Sync but my implementation provides

(&Locked<T>, &Guard) -> &T

whereas the implementation you linked only provides

(&Locked<T>, &mut Guard) -> &mut T

if T is not Sync (thereby also requiring that the underlying lock is not re-entrant).

Both seem to be useful depending on the circumstances but in my usecase I need to access multiple fields at the same time.