linux-kernel - Re: [PATCH 4/4] net: mac80211: mlme.c: Add lockdep condition for RCU list usage

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Date:   Fri, 24 Apr 2020 11:24:40 +0200
From:   Johannes Berg <johannes@...solutions.net>
To:     madhuparnabhowmik10@...il.com, davem@...emloft.net, kuba@...nel.org
Cc:     linux-wireless@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, frextrite@...il.com,
        joel@...lfernandes.org, paulmck@...nel.org,
        linux-kernel-mentees@...ts.linuxfoundation.org
Subject: Re: [PATCH 4/4] net: mac80211: mlme.c: Add lockdep condition for
 RCU list usage

On Thu, 2020-04-09 at 13:59 +0530, madhuparnabhowmik10@...il.com wrote:
> From: Madhuparna Bhowmik <madhuparnabhowmik10@...il.com>
> 
> ieee80211_add_vht_ie() is called with sdata->wdev.mtx held from
> ieee80211_send_assoc(). Add lockdep condition to avoid false positive
> warnings.

Again, wrong lock!

Over the course of the three patches, you've now claimed that any one of

 * RTNL,
 * local->iflist_mtx,
 * local->mtx, and
 * sdata->wdev.mtx

are sufficient to iterate the interface list, but only the first two are
really true.

johannes