On Sun, Jan 08, 2023 at 10:13:22PM +0100, Martin Blumenstingl wrote:
> USB and (upcoming) SDIO support may sleep in the read/write handlers.
> Shrink the RCU critical section so it only cover the call to
> ieee80211_find_sta() and finding the ic_vht_cap/vht_cap based on the
> found station. This moves the chip's BFEE configuration outside the
> rcu_read_lock section and thus prevent "scheduling while atomic" or
> "Voluntary context switch within RCU read-side critical section!"
> warnings when accessing the registers using an SDIO card (which is
> where this issue has been spotted in the real world - but it also
> affects USB cards).
Unfortunately this introduces a regression on my RTW8821CU chip. With
this it constantly looses connection to the AP and reconnects shortly
after:
[ 199.771143] wlan0: authenticate with b0:be:76:5e:7b:34
[ 201.447301] wlan0: send auth to b0:be:76:5e:7b:34 (try 1/3)
[ 201.456789] wlan0: authenticated
[ 201.462356] wlan0: associate with b0:be:76:5e:7b:34 (try 1/3)
[ 201.477263] wlan0: RX AssocResp from b0:be:76:5e:7b:34 (capab=0x431 status=0 aid=2)
[ 201.512995] wlan0: associated
[ 213.790399] wlan0: authenticate with b0:be:76:5e:7b:34
[ 215.467302] wlan0: send auth to b0:be:76:5e:7b:34 (try 1/3)
[ 215.470532] wlan0: authenticated
[ 215.490355] wlan0: associate with b0:be:76:5e:7b:34 (try 1/3)
[ 215.503777] wlan0: RX AssocResp from b0:be:76:5e:7b:34 (capab=0x431 status=0 aid=2)
[ 215.539608] wlan0: associated
[ 227.770596] wlan0: authenticate with b0:be:76:5e:7b:34
[ 229.443302] wlan0: send auth to b0:be:76:5e:7b:34 (try 1/3)
[ 229.451209] wlan0: authenticated
[ 229.462487] wlan0: associate with b0:be:76:5e:7b:34 (try 1/3)
[ 229.476077] wlan0: RX AssocResp from b0:be:76:5e:7b:34 (capab=0x431 status=0 aid=2)
[ 229.513499] wlan0: associated
[ 241.738494] wlan0: authenticate with b0:be:76:5e:7b:34
[ 243.407301] wlan0: send auth to b0:be:76:5e:7b:34 (try 1/3)
[ 243.411207] wlan0: authenticated
[ 243.423213] wlan0: associate with b0:be:76:5e:7b:34 (try 1/3)
[ 243.439822] wlan0: RX AssocResp from b0:be:76:5e:7b:34 (capab=0x431 status=0 aid=2)
[ 243.476731] wlan0: associated
I haven't got any further information yet, I just realized this when I
rebased my own RTW88 bugfix series from v6.2.2 to v6.3-rc4 before
sending it.
RTW8723D and RTW8822CU seem unaffected though.
Sascha
>
> Reviewed-by: Ping-Ke Shih <pkshih@xxxxxxxxxxx>
> Tested-by: Sascha Hauer <s.hauer@xxxxxxxxxxxxxx>
> Signed-off-by: Martin Blumenstingl <martin.blumenstingl@xxxxxxxxxxxxxx>
> ---
> v1 -> v2:
> - Added Ping-Ke's Reviewed-by (thank you!)
>
> v2 -> v3:
> - Added Sascha's Tested-by (thank you!)
> - added "wifi" prefix to the subject and reworded the title accordingly
>
>
> drivers/net/wireless/realtek/rtw88/bf.c | 13 +++++++------
> 1 file changed, 7 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/net/wireless/realtek/rtw88/bf.c b/drivers/net/wireless/realtek/rtw88/bf.c
> index 038a30b170ef..c827c4a2814b 100644
> --- a/drivers/net/wireless/realtek/rtw88/bf.c
> +++ b/drivers/net/wireless/realtek/rtw88/bf.c
> @@ -49,19 +49,23 @@ void rtw_bf_assoc(struct rtw_dev *rtwdev, struct ieee80211_vif *vif,
>
> sta = ieee80211_find_sta(vif, bssid);
> if (!sta) {
> + rcu_read_unlock();
> +
> rtw_warn(rtwdev, "failed to find station entry for bss %pM\n",
> bssid);
> - goto out_unlock;
> + return;
> }
>
> ic_vht_cap = &hw->wiphy->bands[NL80211_BAND_5GHZ]->vht_cap;
> vht_cap = &sta->deflink.vht_cap;
>
> + rcu_read_unlock();
> +
> if ((ic_vht_cap->cap & IEEE80211_VHT_CAP_MU_BEAMFORMEE_CAPABLE) &&
> (vht_cap->cap & IEEE80211_VHT_CAP_MU_BEAMFORMER_CAPABLE)) {
> if (bfinfo->bfer_mu_cnt >= chip->bfer_mu_max_num) {
> rtw_dbg(rtwdev, RTW_DBG_BF, "mu bfer number over limit\n");
> - goto out_unlock;
> + return;
> }
>
> ether_addr_copy(bfee->mac_addr, bssid);
> @@ -75,7 +79,7 @@ void rtw_bf_assoc(struct rtw_dev *rtwdev, struct ieee80211_vif *vif,
> (vht_cap->cap & IEEE80211_VHT_CAP_SU_BEAMFORMER_CAPABLE)) {
> if (bfinfo->bfer_su_cnt >= chip->bfer_su_max_num) {
> rtw_dbg(rtwdev, RTW_DBG_BF, "su bfer number over limit\n");
> - goto out_unlock;
> + return;
> }
>
> sound_dim = vht_cap->cap &
> @@ -98,9 +102,6 @@ void rtw_bf_assoc(struct rtw_dev *rtwdev, struct ieee80211_vif *vif,
>
> rtw_chip_config_bfee(rtwdev, rtwvif, bfee, true);
> }
> -
> -out_unlock:
> - rcu_read_unlock();
> }
>
> void rtw_bf_init_bfer_entry_mu(struct rtw_dev *rtwdev,
> --
> 2.39.0
>
>
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