This was noticed in cockroachdb/cockroach#81511.

This field is declared to be atomic:

Yet we read from it non-atomically here:

A trivial fix would be to update the read-site to read atomically.

While we're in here, we should audit the read/write call-sites to make sure we're honoring the atomic call-site.

It may even be worth some sugar in the struct to highlight the fact that the field is atomic (i.e. block.atomic.writer). I believe I've seen this patten adopted elsewhere.