Revert "wifi: wilc1000: convert list management to RCU"

This reverts commit f236464f1db7bea80075e6e31ac70dc6eb80547f

Commit f236464f1db7 ("wifi: wilc1000: convert list management to RCU")
replaced SRCU with RCU, aiming to simplify RCU usage in the driver. No
documentation or commit history hinted about why SRCU has been preferred
in original design, so it has been assumed to be safe to do this
conversion.
Unfortunately, some static analyzers raised warnings, confirmed by runtime
checker, not long after the merge. At least three different issues arose
when switching to RCU:
- wilc_wlan_txq_filter_dup_tcp_ack is executed in a RCU read critical
  section yet calls wait_for_completion_timeout
- wilc_wfi_init_mon_interface calls kmalloc and register_netdevice while
  manipulating a vif retrieved from vif list
- set_channel sends command to chip (and so, also waits for a completion)
  while holding a vif retrieved from vif list (so, in RCU read critical
  section)

Some of those issues are not trivial to fix and would need bigger driver
rework. Fix those issues by reverting the SRCU to RCU conversion commit

Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
Closes: https://lore.kernel.org/linux-wireless/3b46ec7c-baee-49fd-b760-3bc12fb12eaf@moroto.mountain/
Fixes: f236464f1db7 ("wifi: wilc1000: convert list management to RCU")
Signed-off-by: Alexis Lothoré <alexis.lothore@bootlin.com>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://msgid.link/20240528-wilc_revert_srcu_to_rcu-v1-1-bce096e0798c@bootlin.com

1 files changed, 24 insertions, 17 deletions

diff --git a/drivers/net/wireless/microchip/wilc1000/cfg80211.c b/drivers/net/wireless/microchip/wilc1000/cfg80211.c
index 7d9fb9f2d527..089102ed9ae5 100644
--- a/drivers/net/wireless/microchip/wilc1000/cfg80211.c
+++ b/drivers/net/wireless/microchip/wilc1000/cfg80211.c
@@ -237,11 +237,12 @@ static int set_channel(struct wiphy *wiphy,
 	struct wilc_vif *vif;
 	u32 channelnum;
 	int result;
+	int srcu_idx;
 
-	rcu_read_lock();
+	srcu_idx = srcu_read_lock(&wl->srcu);
 	vif = wilc_get_wl_to_vif(wl);
 	if (IS_ERR(vif)) {
-		rcu_read_unlock();
+		srcu_read_unlock(&wl->srcu, srcu_idx);
 		return PTR_ERR(vif);
 	}
 
@@ -252,7 +253,7 @@ static int set_channel(struct wiphy *wiphy,
 	if (result)
 		netdev_err(vif->ndev, "Error in setting channel\n");
 
-	rcu_read_unlock();
+	srcu_read_unlock(&wl->srcu, srcu_idx);
 	return result;
 }
 
@@ -805,8 +806,9 @@ static int set_wiphy_params(struct wiphy *wiphy, u32 changed)
 	struct wilc *wl = wiphy_priv(wiphy);
 	struct wilc_vif *vif;
 	struct wilc_priv *priv;
+	int srcu_idx;
 
-	rcu_read_lock();
+	srcu_idx = srcu_read_lock(&wl->srcu);
 	vif = wilc_get_wl_to_vif(wl);
 	if (IS_ERR(vif))
 		goto out;
@@ -861,7 +863,7 @@ static int set_wiphy_params(struct wiphy *wiphy, u32 changed)
 		netdev_err(priv->dev, "Error in setting WIPHY PARAMS\n");
 
 out:
-	rcu_read_unlock();
+	srcu_read_unlock(&wl->srcu, srcu_idx);
 	return ret;
 }
 
@@ -1537,19 +1539,20 @@ static struct wireless_dev *add_virtual_intf(struct wiphy *wiphy,
 
 	if (type == NL80211_IFTYPE_MONITOR) {
 		struct net_device *ndev;
+		int srcu_idx;
 
-		rcu_read_lock();
+		srcu_idx = srcu_read_lock(&wl->srcu);
 		vif = wilc_get_vif_from_type(wl, WILC_AP_MODE);
 		if (!vif) {
 			vif = wilc_get_vif_from_type(wl, WILC_GO_MODE);
 			if (!vif) {
-				rcu_read_unlock();
+				srcu_read_unlock(&wl->srcu, srcu_idx);
 				goto validate_interface;
 			}
 		}
 
 		if (vif->monitor_flag) {
-			rcu_read_unlock();
+			srcu_read_unlock(&wl->srcu, srcu_idx);
 			goto validate_interface;
 		}
 
@@ -1557,12 +1560,12 @@ static struct wireless_dev *add_virtual_intf(struct wiphy *wiphy,
 		if (ndev) {
 			vif->monitor_flag = 1;
 		} else {
-			rcu_read_unlock();
+			srcu_read_unlock(&wl->srcu, srcu_idx);
 			return ERR_PTR(-EINVAL);
 		}
 
 		wdev = &vif->priv.wdev;
-		rcu_read_unlock();
+		srcu_read_unlock(&wl->srcu, srcu_idx);
 		return wdev;
 	}
 
@@ -1610,7 +1613,7 @@ static int del_virtual_intf(struct wiphy *wiphy, struct wireless_dev *wdev)
 	list_del_rcu(&vif->list);
 	wl->vif_num--;
 	mutex_unlock(&wl->vif_mutex);
-	synchronize_rcu();
+	synchronize_srcu(&wl->srcu);
 	return 0;
 }
 
@@ -1635,23 +1638,25 @@ static void wilc_set_wakeup(struct wiphy *wiphy, bool enabled)
 {
 	struct wilc *wl = wiphy_priv(wiphy);
 	struct wilc_vif *vif;
+	int srcu_idx;
 
-	rcu_read_lock();
+	srcu_idx = srcu_read_lock(&wl->srcu);
 	vif = wilc_get_wl_to_vif(wl);
 	if (IS_ERR(vif)) {
-		rcu_read_unlock();
+		srcu_read_unlock(&wl->srcu, srcu_idx);
 		return;
 	}
 
 	netdev_info(vif->ndev, "cfg set wake up = %d\n", enabled);
 	wilc_set_wowlan_trigger(vif, enabled);
-	rcu_read_unlock();
+	srcu_read_unlock(&wl->srcu, srcu_idx);
 }
 
 static int set_tx_power(struct wiphy *wiphy, struct wireless_dev *wdev,
 			enum nl80211_tx_power_setting type, int mbm)
 {
 	int ret;
+	int srcu_idx;
 	s32 tx_power = MBM_TO_DBM(mbm);
 	struct wilc *wl = wiphy_priv(wiphy);
 	struct wilc_vif *vif;
@@ -1659,10 +1664,10 @@ static int set_tx_power(struct wiphy *wiphy, struct wireless_dev *wdev,
 	if (!wl->initialized)
 		return -EIO;
 
-	rcu_read_lock();
+	srcu_idx = srcu_read_lock(&wl->srcu);
 	vif = wilc_get_wl_to_vif(wl);
 	if (IS_ERR(vif)) {
-		rcu_read_unlock();
+		srcu_read_unlock(&wl->srcu, srcu_idx);
 		return -EINVAL;
 	}
 
@@ -1674,7 +1679,7 @@ static int set_tx_power(struct wiphy *wiphy, struct wireless_dev *wdev,
 	ret = wilc_set_tx_power(vif, tx_power);
 	if (ret)
 		netdev_err(vif->ndev, "Failed to set tx power\n");
-	rcu_read_unlock();
+	srcu_read_unlock(&wl->srcu, srcu_idx);
 
 	return ret;
 }
@@ -1757,6 +1762,7 @@ static void wlan_init_locks(struct wilc *wl)
 	init_completion(&wl->cfg_event);
 	init_completion(&wl->sync_event);
 	init_completion(&wl->txq_thread_started);
+	init_srcu_struct(&wl->srcu);
 }
 
 void wlan_deinit_locks(struct wilc *wilc)
@@ -1767,6 +1773,7 @@ void wlan_deinit_locks(struct wilc *wilc)
 	mutex_destroy(&wilc->txq_add_to_head_cs);
 	mutex_destroy(&wilc->vif_mutex);
 	mutex_destroy(&wilc->deinit_lock);
+	cleanup_srcu_struct(&wilc->srcu);
 }
 
 int wilc_cfg80211_init(struct wilc **wilc, struct device *dev, int io_type,