linux-kernel - Re: [PATCH RFC v1 3/7] rtw88: Use rtw_iterate_stas where the iterator reads or writes registers

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Date:   Mon, 19 Jul 2021 08:36:04 +0200
From:   Johannes Berg <johannes@...solutions.net>
To:     Martin Blumenstingl <martin.blumenstingl@...glemail.com>,
        linux-wireless@...r.kernel.org
Cc:     tony0620emma@...il.com, kvalo@...eaurora.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        Neo Jou <neojou@...il.com>,
        Jernej Skrabec <jernej.skrabec@...il.com>
Subject: Re: [PATCH RFC v1 3/7] rtw88: Use rtw_iterate_stas where the
 iterator reads or writes registers

On Sat, 2021-07-17 at 22:40 +0200, Martin Blumenstingl wrote:
> 
> --- a/drivers/net/wireless/realtek/rtw88/mac80211.c
> +++ b/drivers/net/wireless/realtek/rtw88/mac80211.c
> @@ -721,7 +721,7 @@ static void rtw_ra_mask_info_update(struct rtw_dev *rtwdev,
>  	br_data.rtwdev = rtwdev;
>  	br_data.vif = vif;
>  	br_data.mask = mask;
> -	rtw_iterate_stas_atomic(rtwdev, rtw_ra_mask_info_update_iter, &br_data);
> +	rtw_iterate_stas(rtwdev, rtw_ra_mask_info_update_iter, &br_data);

And then you pretty much immediately break that invariant here, namely
that you're calling this within the set_bitrate_mask() method called by
mac80211.

That's not actually fundamentally broken today, but it does *severely*
restrict what we can do in mac80211 wrt. locking, and I really don't
want to keep the dozen or so locks forever, this needs simplification
because clearly we don't even know what should be under what lock.

So like I said on the other patch, I don't have a fundamental objection
to taking such a patch, but the locking mess that this gets us into is
something I'd rather not have.

Maybe just don't support set_bitrate_mask for SDIO drivers for now?

The other cases look OK, it's being called from outside contexts
(wowlan, etc.)

johannes