Jann Horn [off-list ref] wrote:

Does this mean that refcount_read() isn't sufficient for what you want
to do with tracing (because for some reason you actually need to know
the values atomically at the time of increment/decrement)?

Correct.  There's a gap and if an interrupt or something occurs, it's
sufficiently big for the refcount trace to go weird.

I've seen it in afs/rxrpc where the incoming network packets that are part of
the rxrpc call flow disrupt the refcounts noted in trace lines.

David