If implementation is task based and task always runs on same virtual CPU (slots equaling CPUs or parallelism), wonder if something like below might help.

RW lock could be implemented using an array of length equal to slots and proper padding to ensure each slot is in its own face line (avoid invalidating CPU cache when different slot is read/written).

For read lock: Each task acquires the lock for their slot.

For write lock: Acquire lock from left most slot to right. Writes can starve readers when they block on in-flight reader at a different slot when moving from left to right.

I do not know how Rust RW locks are implemented.