wg_noise: Remove atomics for kp pointers.

[jhb]

Summary

Atomics are not needed to read the pointers inside of an epoch
due to fences in epoch_*.

Almost all other accesses were under a mutex.

There is one unlocked read of the pointer for which the atomic
load doesn't do anything (in terms of limiting races).

[emaste]

There is one unlocked read of the pointer for which the atomic load doesn't do anything (in terms of limiting races).

Does it make sense for this case to have a comment (i.e., explaining why the race is not important)?

[jhb]

sys/dev/wg/wg_noise.c

730

This is the unlocked read and it's just an optimization to avoid the lock below (and not an uncommon pattern, so I think it is obvious in context)

[emaste]

sys/dev/wg/wg_noise.c

730

Fair enough, I did not look at each case to find the unlocked read and when pointed out in context it's clear enough to me. [That said I don't think a comment wouldn't be out of place]