linux-kernel - [PATCH v3 6/8] rtw88: Configure the registers from rtw_bf

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Date:   Sat,  8 Jan 2022 01:55:31 +0100
From:   Martin Blumenstingl <martin.blumenstingl@...glemail.com>
To:     linux-wireless@...r.kernel.org
Cc:     tony0620emma@...il.com, kvalo@...eaurora.org,
        johannes@...solutions.net, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, Neo Jou <neojou@...il.com>,
        Jernej Skrabec <jernej.skrabec@...il.com>,
        Pkshih <pkshih@...ltek.com>, Ed Swierk <eswierk@...st>,
        Martin Blumenstingl <martin.blumenstingl@...glemail.com>
Subject: [PATCH v3 6/8] rtw88: Configure the registers from rtw_bf_assoc() outside the RCU lock

Upcoming SDIO support may sleep in the read/write handlers. Shrink the
RCU critical section so it only cover the ieee80211_find_sta() call 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 a "scheduling while atomic" issue when accessing the registers
using an SDIO card.

Signed-off-by: Martin Blumenstingl <martin.blumenstingl@...glemail.com>
---
v2 -> v3:
- no changes

v1 -> v2:
- shrink the critical section as suggested by Ping-Ke

 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 df750b3a35e9..792eb9930269 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->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,
-- 
2.34.1