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
Hi Johannes, Hi Ping-Ke,
On Mon, Jul 19, 2021 at 8:36 AM Johannes Berg <[email protected]> wrote:
>
> 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.
you are right, I was not aware of this
> 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.
To me it's also not clear what the goal of the whole locking is.
The lock in ieee80211_iterate_stations_atomic is obviously for the
mac80211-internal state-machine
But I *believe* that there's a second purpose (rtw88 specific) -
here's my understanding of that part:
- rtw_sta_info contains a "mac_id" which is an identifier for a
specific station used by the rtw88 driver and is shared with the
firmware
- rtw_ops_sta_{add,remove} uses rtwdev->mutex to protect the rtw88
side of this "mac_id" identifier
- (for some reason rtw_update_sta_info doesn't use rtwdev->mutex)
So now I am wondering if the ieee80211_iterate_stations_atomic lock is
also used to protect any modifications to rtw_sta_info.
Ping-Ke, I am wondering if the attached patch (untested - to better
demonstrate what I want to say) would:
- allow us to move the register write outside of
ieee80211_iterate_stations_atomic
- mean we can keep ieee80211_iterate_stations_atomic (instead of the
non-atomic variant)
- protect the code managing the "mac_id" with rtwdev->mutex consistently
> The other cases look OK, it's being called from outside contexts
> (wowlan, etc.)
Thanks for reviewing this Johannes!
Best regards,
Martin