Received-SPF: pass (google.com: domain of linux-wireless-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
MIME-Version: 1.0
References: <20220108005533.947787-1-martin.blumenstingl@googlemail.com>
 <423f474e15c948eda4db5bc9a50fd391@realtek.com> <CAFBinCBVEndU0t-6d5atE31OFYHzPyk7pOe78v0XrrFWcBec9w@mail.gmail.com>
 <5ef8ab4f78e448df9f823385d0daed88@realtek.com> <CAFBinCDjfKK3+WOXP2xbcAK-KToWof+kSzoxYztqRcc=7T1eyg@mail.gmail.com>
 <53bea965043548539b995514d36f48e5@realtek.com>
In-Reply-To: <53bea965043548539b995514d36f48e5@realtek.com>
From:   Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Date:   Sun, 30 Jan 2022 22:40:06 +0100
Message-ID: <CAFBinCBcgEKB3Zak9oGrZ-azqgot691gFSRGGeOP-hr4e+9C4Q@mail.gmail.com>
Subject: Re: [PATCH v3 0/8] rtw88: prepare locking for SDIO support
To:     Pkshih <pkshih@realtek.com>
Cc:     "linux-wireless@vger.kernel.org" <linux-wireless@vger.kernel.org>,
        "tony0620emma@gmail.com" <tony0620emma@gmail.com>,
        "kvalo@codeaurora.org" <kvalo@codeaurora.org>,
        "johannes@sipsolutions.net" <johannes@sipsolutions.net>,
        "netdev@vger.kernel.org" <netdev@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Neo Jou <neojou@gmail.com>,
        Jernej Skrabec <jernej.skrabec@gmail.com>,
        Ed Swierk <eswierk@gh.st>
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

Hi Ping-Ke,

On Fri, Jan 28, 2022 at 1:51 AM Pkshih <pkshih@realtek.com> wrote:
[...]
>
> > >
> > > To avoid this, we can add a flag to struct rtw_vif, and set this flag
> > > when ::remove_interface. Then, only collect vif without this flag into list
> > > when we use iterate_actiom().
> > >
> > > As well as ieee80211_sta can do similar fix.
> > >
>
> I would prefer my method that adds a 'bool disabled' flag to struct rtw_vif/rtw_sta
> and set it when ::remove_interface/::sta_remove. Then rtw_iterate_stas() can
> check this flag to decide whether does thing or not.
That would indeed be a very straight forward approach and easy to read.
In net/mac80211/iface.c there's some cases where after
drv_remove_interface() (which internally calls our .remove_interface
op) will kfree the vif (sdata). Doesn't that then result in a
use-after-free if we rely on a boolean within rtw_vif?

[...]
> > For the interface use-case it's not clear to me how this works at all.
> > rtw_ops_add_interface() has (in a simplified view):
> >     u8 port = 0;
> >     // the port variable is never changed
> >     rtwvif->port = port;
> >     rtwvif->conf = &rtw_vif_port[port];
> >     rtw_info(rtwdev, "start vif %pM on port %d\n", vif->addr, rtwvif->port);
> > How do multiple interfaces (vifs) work in rtw88 if the port is always
> > zero? Is some kind of tracking of the used ports missing (similar to
> > how we track the used station IDs - also called mac_id - in
> > rtw_dev->mac_id_map)?
>
> The port should be allocated dynamically if we support two or more vifs.
> We have internal tree that is going to support p2p by second vif.
I see, thanks for clarifying this!


Best regards,
Martin