On 5/30/2024 7:24 PM, Baochen Qiang wrote:
> Current documentation on RCU in ath11k_mac_op_ipv6_changed() says:
>
> /* Note: read_lock_bh() calls rcu_read_lock() */
> read_lock_bh(&idev->lock);
>
> This is wrong because without enabling CONFIG_PREEMPT_RT
> rcu_read_lock() is not called by read_lock_bh(). The reason
> why current code works even in a CONFIG_PREEMPT_RT=n kernel
> is because atomic_notifier_call_chain() already does that for
> us, see:
>
> int atomic_notifier_call_chain()
> {
> ...
> rcu_read_lock();
> ret = notifier_call_chain(&nh->head, val, v, -1, NULL);
> rcu_read_unlock();
> ...
> }
>
> and backtrace:
>
> ath11k_mac_op_ipv6_changed
> ieee80211_ifa6_changed
> notifier_call_chain
> atomic_notifier_call_chain
>
> So update the comment to make it correct.
>
> This is found during code review, compile tested only.
>
> Fixes: feafe59c8975 ("wifi: ath11k: use RCU when accessing struct inet6_dev::ac_list")
> Signed-off-by: Baochen Qiang <quic_bqiang@xxxxxxxxxxx>
Acked-by: Jeff Johnson <quic_jjohnson@xxxxxxxxxxx>
