df4684: === mode 2: rcu_barrier() no-op vs module unload ===
df4684: call_rcu enqueued (callback 0xffffffff82eb0020 fires in >=1s)
df4684: dummy RCU callback executed (module text 0xffffffff82eb0020 still mapped)
df4684: rcu_barrier() returned (no-op on this port) M-bM^@M^T kldunload NOW; the pending callback will execute into unmapped module text ~1s later
df4684: === mode 2 armed M-bM^@M^T run: kldunload df4684; sleep 3 ===
df4684: unloading