RE: [PATCH v3 0/8] rtw88: prepare locking for SDIO support

From: Pkshih <pkshih@realtek.com>
To: Martin Blumenstingl <martin.blumenstingl@googlemail.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>
Subject: RE: [PATCH v3 0/8] rtw88: prepare locking for SDIO support
Date: Fri, 28 Jan 2022 00:51:11 +0000	[thread overview]
Message-ID: <53bea965043548539b995514d36f48e5@realtek.com> (raw)
In-Reply-To: <CAFBinCDjfKK3+WOXP2xbcAK-KToWof+kSzoxYztqRcc=7T1eyg@mail.gmail.com>

Hi,

> -----Original Message-----
> From: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
> Sent: Friday, January 28, 2022 5:53 AM
> To: Pkshih <pkshih@realtek.com>
> Cc: linux-wireless@vger.kernel.org; tony0620emma@gmail.com; kvalo@codeaurora.org;
> johannes@sipsolutions.net; netdev@vger.kernel.org; linux-kernel@vger.kernel.org; Neo Jou
> <neojou@gmail.com>; Jernej Skrabec <jernej.skrabec@gmail.com>; Ed Swierk <eswierk@gh.st>
> Subject: Re: [PATCH v3 0/8] rtw88: prepare locking for SDIO support
> 
> Hi Ping-Ke,
> 
> On Mon, Jan 24, 2022 at 3:59 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.

[...]

> 
> For the sta use-case I thought about adding a dedicated rwlock
> (include/linux/rwlock.h) for rtw_dev->mac_id_map.
> rtw_sta_{add,remove} would take a write-lock.
> rtw_iterate_stas() takes the read-lock (the lock would be acquired
> before calling into ieee80211_iterate_...). Additionally
> rtw_iterate_stas() needs to check if the station is still valid
> according to mac_id_map - if not: skip/ignore it for that iteration.
> This could be combined with your
> 0001-rtw88-use-atomic-to-collect-stas-and-does-iterators.patch.

Using a 'disabled' flag within rtw_vif/rtw_sta will be intuitive and
better than bitmap of mac_id_map. Please reference my mention above.

> 
> 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.

Ping-Ke