[v1] rtw88: Four fixes found while working on SDIO support

[PATCH 2/4] rtw88: Configure the registers from rtw_bf_assoc() outside the RCU lock

Posted by Martin Blumenstingl 3 years, 1 month ago

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).

Reviewed-by: Ping-Ke Shih <pkshih@realtek.com>
Signed-off-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
---
 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

Re: [PATCH 2/4] rtw88: Configure the registers from rtw_bf_assoc() outside the RCU lock

Posted by Ping-Ke Shih 3 years, 1 month ago

On Thu, 2022-12-29 at 13:48 +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).
> 
> Reviewed-by: Ping-Ke Shih <pkshih@realtek.com>
> Signed-off-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>

I think my reviewed-by should behind your signed-off-by.

> ---
>  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,

Re: [PATCH 2/4] rtw88: Configure the registers from rtw_bf_assoc() outside the RCU lock

Posted by Martin Blumenstingl 3 years, 1 month ago

Hi Ping-Ke,

On Fri, Dec 30, 2022 at 12:48 AM Ping-Ke Shih <pkshih@realtek.com> wrote:
[...]
> > Reviewed-by: Ping-Ke Shih <pkshih@realtek.com>
> > Signed-off-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
>
> I think my reviewed-by should behind your signed-off-by.
My understanding is that I have to put your Reviewed-by above my
Signed-off-by since I added the Reviewed-by to the description.
If the maintainer adds your Reviewed-by while applying the patch to
the tree they will put your Reviewed-by between my Signed-off-by and
the maintainer's Signed-off-by.

If this is incorrect then please let me know and I'll change it for v3.


Best regards,
Martin

RE: [PATCH 2/4] rtw88: Configure the registers from rtw_bf_assoc() outside the RCU lock

Posted by Ping-Ke Shih 3 years, 1 month ago


> -----Original Message-----
> From: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
> Sent: Wednesday, January 4, 2023 11:44 PM
> To: Ping-Ke Shih <pkshih@realtek.com>
> Cc: linux-wireless@vger.kernel.org; kvalo@kernel.org; s.hauer@pengutronix.de; tony0620emma@gmail.com;
> netdev@vger.kernel.org; linux-kernel@vger.kernel.org
> Subject: Re: [PATCH 2/4] rtw88: Configure the registers from rtw_bf_assoc() outside the RCU lock
> 
> Hi Ping-Ke,
> 
> On Fri, Dec 30, 2022 at 12:48 AM Ping-Ke Shih <pkshih@realtek.com> wrote:
> [...]
> > > Reviewed-by: Ping-Ke Shih <pkshih@realtek.com>
> > > Signed-off-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
> >
> > I think my reviewed-by should behind your signed-off-by.
> My understanding is that I have to put your Reviewed-by above my
> Signed-off-by since I added the Reviewed-by to the description.
> If the maintainer adds your Reviewed-by while applying the patch to
> the tree they will put your Reviewed-by between my Signed-off-by and
> the maintainer's Signed-off-by.
> 
> If this is incorrect then please let me know and I'll change it for v3.
> 

My original thought is to add my reviewed-by in the order like maintainer
applies the patch, but your understanding looks reasonable. Sorry for the noise.

Ping-Ke