mac80211: RCU-ify STA info structure access

This makes access to the STA hash table/list use RCU to protect
against freeing of items. However, it's not a true RCU, the
copy step is missing: whenever somebody changes a STA item it
is simply updated. This is an existing race condition that is
now somewhat understandable.

This patch also fixes the race key freeing vs. STA destruction
by making sure that sta_info_destroy() is always called under
RTNL and frees the key.

Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

1 files changed, 18 insertions, 13 deletions

diff --git a/drivers/net/wireless/iwlwifi/iwl-3945-rs.c b/drivers/net/wireless/iwlwifi/iwl-3945-rs.c
index a8223c4cc97..c4bfba6f3c2 100644
--- a/drivers/net/wireless/iwlwifi/iwl-3945-rs.c
+++ b/drivers/net/wireless/iwlwifi/iwl-3945-rs.c
@@ -471,10 +471,11 @@ static void rs_tx_status(void *priv_rate,
 		return;
 	}
 
+	rcu_read_lock();
+
 	sta = sta_info_get(local, hdr->addr1);
 	if (!sta || !sta->rate_ctrl_priv) {
-		if (sta)
-			sta_info_put(sta);
+		rcu_read_unlock();
 		IWL_DEBUG_RATE("leave: No STA priv data to update!\n");
 		return;
 	}
@@ -547,7 +548,7 @@ static void rs_tx_status(void *priv_rate,
 
 	spin_unlock_irqrestore(&rs_sta->lock, flags);
 
-	sta_info_put(sta);
+	rcu_read_unlock();
 
 	IWL_DEBUG_RATE("leave\n");
 
@@ -658,6 +659,8 @@ static void rs_get_rate(void *priv_rate, struct net_device *dev,
 
 	IWL_DEBUG_RATE("enter\n");
 
+	rcu_read_lock();
+
 	sta = sta_info_get(local, hdr->addr1);
 
 	/* Send management frames and broadcast/multicast data using lowest
@@ -668,8 +671,7 @@ static void rs_get_rate(void *priv_rate, struct net_device *dev,
 	    !sta || !sta->rate_ctrl_priv) {
 		IWL_DEBUG_RATE("leave: No STA priv data to update!\n");
 		sel->rate = rate_lowest(local, band, sta);
-		if (sta)
-			sta_info_put(sta);
+		rcu_read_unlock();
 		return;
 	}
 
@@ -811,7 +813,7 @@ static void rs_get_rate(void *priv_rate, struct net_device *dev,
 	else
 		sta->txrate_idx = sta->last_txrate_idx;
 
-	sta_info_put(sta);
+	rcu_read_unlock();
 
 	IWL_DEBUG_RATE("leave: %d\n", index);
 
@@ -843,13 +845,15 @@ int iwl3945_fill_rs_info(struct ieee80211_hw *hw, char *buf, u8 sta_id)
 	unsigned long now = jiffies;
 	u32 max_time = 0;
 
+	rcu_read_lock();
+
 	sta = sta_info_get(local, priv->stations[sta_id].sta.sta.addr);
 	if (!sta || !sta->rate_ctrl_priv) {
-		if (sta) {
-			sta_info_put(sta);
+		if (sta)
 			IWL_DEBUG_RATE("leave - no private rate data!\n");
-		} else
+		else
 			IWL_DEBUG_RATE("leave - no station!\n");
+		rcu_read_unlock();
 		return sprintf(buf, "station %d not found\n", sta_id);
 	}
 
@@ -890,7 +894,7 @@ int iwl3945_fill_rs_info(struct ieee80211_hw *hw, char *buf, u8 sta_id)
 		i = j;
 	}
 	spin_unlock_irqrestore(&rs_sta->lock, flags);
-	sta_info_put(sta);
+	rcu_read_unlock();
 
 	/* Display the average rate of all samples taken.
 	 *
@@ -927,11 +931,12 @@ void iwl3945_rate_scale_init(struct ieee80211_hw *hw, s32 sta_id)
 		return;
 	}
 
+	rcu_read_lock();
+
 	sta = sta_info_get(local, priv->stations[sta_id].sta.sta.addr);
 	if (!sta || !sta->rate_ctrl_priv) {
-		if (sta)
-			sta_info_put(sta);
 		IWL_DEBUG_RATE("leave - no private rate data!\n");
+		rcu_read_unlock();
 		return;
 	}
 
@@ -958,7 +963,7 @@ void iwl3945_rate_scale_init(struct ieee80211_hw *hw, s32 sta_id)
 		break;
 	}
 
-	sta_info_put(sta);
+	rcu_read_unlock();
 	spin_unlock_irqrestore(&rs_sta->lock, flags);
 
 	rssi = priv->last_rx_rssi;