netdev - Re: [PATCH 2/4] net: mac80211: scan.c: Fix RCU list related warnings.

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Message-ID: <8d6fd8bfa0fb66f8ee4bfd34738a349bb1b7ee59.camel@sipsolutions.net>
Date:   Fri, 24 Apr 2020 11:21:27 +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 2/4] net: mac80211: scan.c: Fix RCU list related
 warnings.

On Thu, 2020-04-09 at 13:58 +0530, madhuparnabhowmik10@...il.com wrote:
> From: Madhuparna Bhowmik <madhuparnabhowmik10@...il.com>
> 
> This patch fixes the following warning:
> 
> WARNING: suspicious RCU usage
> [   84.530619] 5.6.0+ #4 Not tainted
> [   84.530637] -----------------------------
> [   84.530658] net/mac80211/scan.c:454 RCU-list traversed in non-reader section!!
> 
> As local->mtx is held in __ieee80211_scan_completed()

Yeah, but is that really the right lock? I think it should be RTNL or
iflist_mtx for the interface list.

(Not that this is necessarily a good idea - we perhaps should clean up
and significantly reduce the number of locks used here.)

johannes