Re: [PATCH] net: mac80211: rx.c: Use built-in RCU list checking

From: Johannes Berg
Date: Sat Feb 22 2020 - 07:53:58 EST


On Sat, 2020-02-22 at 15:48 +0530, madhuparnabhowmik10@xxxxxxxxx wrote:
> From: Madhuparna Bhowmik <madhuparnabhowmik10@xxxxxxxxx>
>
> list_for_each_entry_rcu() has built-in RCU and lock checking.
>
> Pass cond argument to list_for_each_entry_rcu() to silence
> false lockdep warning when CONFIG_PROVE_RCU_LIST is enabled
> by default.

Umm. What warning?

> +++ b/net/mac80211/rx.c
> @@ -3547,7 +3547,8 @@ static void ieee80211_rx_cooked_monitor(struct ieee80211_rx_data *rx,
> skb->pkt_type = PACKET_OTHERHOST;
> skb->protocol = htons(ETH_P_802_2);
>
> - list_for_each_entry_rcu(sdata, &local->interfaces, list) {
> + list_for_each_entry_rcu(sdata, &local->interfaces, list,
> + lockdep_is_held(&rx->local->rx_path_lock)) {
> if (!ieee80211_sdata_running(sdata))
> continue;

This is not related at all.

> @@ -4114,7 +4115,8 @@ void __ieee80211_check_fast_rx_iface(struct ieee80211_sub_if_data *sdata)
>
> lockdep_assert_held(&local->sta_mtx);
>
> - list_for_each_entry_rcu(sta, &local->sta_list, list) {
> + list_for_each_entry_rcu(sta, &local->sta_list, list,
> + lockdep_is_held(&local->sta_mtx)) {

And this isn't even a real RCU iteration, since we _must_ hold the mutex
here.

johannes