Received-SPF: pass (google.com: domain of linux-wireless-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Message-ID: <a91e755bf3aee9ed7fcd5dd4d8ba5b315312c22b.camel@sipsolutions.net>
Subject: Re: [PATCH] wifi: wilc1000: fix kernel oops during interface down
 during background scan
From:   Johannes Berg <johannes@sipsolutions.net>
To:     Michael Walle <michael@walle.cc>, Ajay.Kathat@microchip.com,
        Kalle Valo <kvalo@kernel.org>
Cc:     linux-wireless@vger.kernel.org, Claudiu.Beznea@microchip.com,
        Sripad.Balwadgi@microchip.com, mwalle@kernel.org
Date:   Tue, 11 Apr 2023 13:24:35 +0200
In-Reply-To: <f10d69fb17e03eb093d846d005d7496a@walle.cc>
References: <20230404012010.15261-1-ajay.kathat@microchip.com>
         <f10d69fb17e03eb093d846d005d7496a@walle.cc>
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
User-Agent: Evolution 3.46.4 (3.46.4-1.fc37) 
MIME-Version: 1.0
Precedence: bulk

On Wed, 2023-04-05 at 13:40 +0200, Michael Walle wrote:
>=20
> wilc_disconnect() is called from the cfg80211_ops::disconnect
> callback. wilc_deinit() is called from net_device_ops::ndo_stop.
> Is there any lock which prevents both functions be called in
> parallel?

I don't _think_ there's any common lock, ndo_stop() holds the RTNL, but
cfg80211 for a normal nl80211 disconnect command will only briefly hold
the RTNL and drop it again before calling into the driver.

The internal flags here don't indicate requiring RTNL and that wouldn't
make much sense either:

        {
                .cmd =3D NL80211_CMD_DISCONNECT,
                .validate =3D GENL_DONT_VALIDATE_STRICT | GENL_DONT_VALIDAT=
E_DUMP,
                .doit =3D nl80211_disconnect,
                .flags =3D GENL_UNS_ADMIN_PERM,
                .internal_flags =3D IFLAGS(NL80211_FLAG_NEED_NETDEV_UP),
        },


See commit a05829a7222e ("cfg80211: avoid holding the RTNL when calling
the driver").


johannes