[MAC80211]: improve locking of sta_info related structures

The sta_info code has some awkward locking which prevents some driver
callbacks from being allowed to sleep. This patch makes the locking more
focused so code that calls driver callbacks are allowed to sleep. It also
converts sta_lock to a rwlock.

Signed-off-by: Michael Wu <flamingice@sourmilk.net>
Signed-off-by: Jiri Benc <jbenc@suse.cz>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

1 files changed, 74 insertions, 110 deletions

diff --git a/net/mac80211/sta_info.c b/net/mac80211/sta_info.c
index ab7b1f067c6e..34245b882c2b 100644
--- a/net/mac80211/sta_info.c
+++ b/net/mac80211/sta_info.c
@@ -32,38 +32,34 @@ static void sta_info_hash_add(struct ieee80211_local *local,
 
 
 /* Caller must hold local->sta_lock */
-static void sta_info_hash_del(struct ieee80211_local *local,
-			      struct sta_info *sta)
+static int sta_info_hash_del(struct ieee80211_local *local,
+			     struct sta_info *sta)
 {
 	struct sta_info *s;
 
 	s = local->sta_hash[STA_HASH(sta->addr)];
 	if (!s)
-		return;
-	if (memcmp(s->addr, sta->addr, ETH_ALEN) == 0) {
+		return -ENOENT;
+	if (s == sta) {
 		local->sta_hash[STA_HASH(sta->addr)] = s->hnext;
-		return;
+		return 0;
 	}
 
-	while (s->hnext && memcmp(s->hnext->addr, sta->addr, ETH_ALEN) != 0)
+	while (s->hnext && s->hnext != sta)
 		s = s->hnext;
-	if (s->hnext)
-		s->hnext = s->hnext->hnext;
-	else
-		printk(KERN_ERR "%s: could not remove STA " MAC_FMT " from "
-		       "hash table\n", local->mdev->name, MAC_ARG(sta->addr));
-}
+	if (s->hnext) {
+		s->hnext = sta->hnext;
+		return 0;
+	}
 
-static inline void __sta_info_get(struct sta_info *sta)
-{
-	kref_get(&sta->kref);
+	return -ENOENT;
 }
 
 struct sta_info *sta_info_get(struct ieee80211_local *local, u8 *addr)
 {
 	struct sta_info *sta;
 
-	spin_lock_bh(&local->sta_lock);
+	read_lock_bh(&local->sta_lock);
 	sta = local->sta_hash[STA_HASH(addr)];
 	while (sta) {
 		if (memcmp(sta->addr, addr, ETH_ALEN) == 0) {
@@ -72,7 +68,7 @@ struct sta_info *sta_info_get(struct ieee80211_local *local, u8 *addr)
 		}
 		sta = sta->hnext;
 	}
-	spin_unlock_bh(&local->sta_lock);
+	read_unlock_bh(&local->sta_lock);
 
 	return sta;
 }
@@ -85,7 +81,7 @@ int sta_info_min_txrate_get(struct ieee80211_local *local)
 	int min_txrate = 9999999;
 	int i;
 
-	spin_lock_bh(&local->sta_lock);
+	read_lock_bh(&local->sta_lock);
 	mode = local->oper_hw_mode;
 	for (i = 0; i < STA_HASH_SIZE; i++) {
 		sta = local->sta_hash[i];
@@ -95,7 +91,7 @@ int sta_info_min_txrate_get(struct ieee80211_local *local)
 			sta = sta->hnext;
 		}
 	}
-	spin_unlock_bh(&local->sta_lock);
+	read_unlock_bh(&local->sta_lock);
 	if (min_txrate == 9999999)
 		min_txrate = 0;
 
@@ -150,7 +146,6 @@ struct sta_info * sta_info_add(struct ieee80211_local *local,
 	sta->rate_ctrl_priv = rate_control_alloc_sta(sta->rate_ctrl, gfp);
 	if (!sta->rate_ctrl_priv) {
 		rate_control_put(sta->rate_ctrl);
-		kref_put(&sta->kref, sta_info_release);
 		kfree(sta);
 		return NULL;
 	}
@@ -162,14 +157,14 @@ struct sta_info * sta_info_add(struct ieee80211_local *local,
 	skb_queue_head_init(&sta->tx_filtered);
 	__sta_info_get(sta);	/* sta used by caller, decremented by
 				 * sta_info_put() */
-	spin_lock_bh(&local->sta_lock);
+	write_lock_bh(&local->sta_lock);
 	list_add(&sta->list, &local->sta_list);
 	local->num_sta++;
 	sta_info_hash_add(local, sta);
-	spin_unlock_bh(&local->sta_lock);
 	if (local->ops->sta_table_notification)
 		local->ops->sta_table_notification(local_to_hw(local),
 						  local->num_sta);
+	write_unlock_bh(&local->sta_lock);
 	sta->key_idx_compression = HW_KEY_IDX_INVALID;
 
 #ifdef CONFIG_MAC80211_VERBOSE_DEBUG
@@ -178,47 +173,25 @@ struct sta_info * sta_info_add(struct ieee80211_local *local,
 #endif /* CONFIG_MAC80211_VERBOSE_DEBUG */
 
 #ifdef CONFIG_MAC80211_DEBUGFS
-	if (!in_interrupt()) {
-		sta->debugfs_registered = 1;
-		ieee80211_sta_debugfs_add(sta);
-		rate_control_add_sta_debugfs(sta);
-	} else {
-		/* debugfs entry adding might sleep, so schedule process
-		 * context task for adding entry for STAs that do not yet
-		 * have one. */
-		queue_work(local->hw.workqueue, &local->sta_debugfs_add);
-	}
+	/* debugfs entry adding might sleep, so schedule process
+	 * context task for adding entry for STAs that do not yet
+	 * have one. */
+	queue_work(local->hw.workqueue, &local->sta_debugfs_add);
 #endif
 
 	return sta;
 }
 
-static void finish_sta_info_free(struct ieee80211_local *local,
-				 struct sta_info *sta)
-{
-#ifdef CONFIG_MAC80211_VERBOSE_DEBUG
-	printk(KERN_DEBUG "%s: Removed STA " MAC_FMT "\n",
-	       local->mdev->name, MAC_ARG(sta->addr));
-#endif /* CONFIG_MAC80211_VERBOSE_DEBUG */
-
-	if (sta->key) {
-		ieee80211_debugfs_key_remove(sta->key);
-		ieee80211_key_free(sta->key);
-		sta->key = NULL;
-	}
-
-	rate_control_remove_sta_debugfs(sta);
-	ieee80211_sta_debugfs_remove(sta);
-
-	sta_info_put(sta);
-}
-
-static void sta_info_remove(struct sta_info *sta)
+/* Caller must hold local->sta_lock */
+void sta_info_remove(struct sta_info *sta)
 {
 	struct ieee80211_local *local = sta->local;
 	struct ieee80211_sub_if_data *sdata;
 
-	sta_info_hash_del(local, sta);
+	/* don't do anything if we've been removed already */
+	if (sta_info_hash_del(local, sta))
+		return;
+
 	list_del(&sta->list);
 	sdata = IEEE80211_DEV_TO_SUB_IF(sta->dev);
 	if (sta->flags & WLAN_STA_PS) {
@@ -228,30 +201,29 @@ static void sta_info_remove(struct sta_info *sta)
 	}
 	local->num_sta--;
 	sta_info_remove_aid_ptr(sta);
+
+	if (local->ops->sta_table_notification)
+		local->ops->sta_table_notification(local_to_hw(local),
+						   local->num_sta);
 }
 
-void sta_info_free(struct sta_info *sta, int locked)
+void sta_info_free(struct sta_info *sta)
 {
 	struct sk_buff *skb;
 	struct ieee80211_local *local = sta->local;
 
-	if (!locked) {
-		spin_lock_bh(&local->sta_lock);
-		sta_info_remove(sta);
-		spin_unlock_bh(&local->sta_lock);
-	} else {
-		sta_info_remove(sta);
-	}
-	if (local->ops->sta_table_notification)
-		local->ops->sta_table_notification(local_to_hw(local),
-						  local->num_sta);
+	might_sleep();
+
+	write_lock_bh(&local->sta_lock);
+	sta_info_remove(sta);
+	write_unlock_bh(&local->sta_lock);
 
 	while ((skb = skb_dequeue(&sta->ps_tx_buf)) != NULL) {
 		local->total_ps_buffered--;
-		dev_kfree_skb_any(skb);
+		dev_kfree_skb(skb);
 	}
 	while ((skb = skb_dequeue(&sta->tx_filtered)) != NULL) {
-		dev_kfree_skb_any(skb);
+		dev_kfree_skb(skb);
 	}
 
 	if (sta->key) {
@@ -276,13 +248,21 @@ void sta_info_free(struct sta_info *sta, int locked)
 		sta->key_idx_compression = HW_KEY_IDX_INVALID;
 	}
 
-#ifdef CONFIG_MAC80211_DEBUGFS
-	if (in_atomic()) {
-		list_add(&sta->list, &local->deleted_sta_list);
-		queue_work(local->hw.workqueue, &local->sta_debugfs_add);
-	} else
-#endif
-		finish_sta_info_free(local, sta);
+#ifdef CONFIG_MAC80211_VERBOSE_DEBUG
+	printk(KERN_DEBUG "%s: Removed STA " MAC_FMT "\n",
+	       local->mdev->name, MAC_ARG(sta->addr));
+#endif /* CONFIG_MAC80211_VERBOSE_DEBUG */
+
+	if (sta->key) {
+		ieee80211_debugfs_key_remove(sta->key);
+		ieee80211_key_free(sta->key);
+		sta->key = NULL;
+	}
+
+	rate_control_remove_sta_debugfs(sta);
+	ieee80211_sta_debugfs_remove(sta);
+
+	sta_info_put(sta);
 }
 
 
@@ -343,13 +323,13 @@ static void sta_info_cleanup(unsigned long data)
 	struct ieee80211_local *local = (struct ieee80211_local *) data;
 	struct sta_info *sta;
 
-	spin_lock_bh(&local->sta_lock);
+	read_lock_bh(&local->sta_lock);
 	list_for_each_entry(sta, &local->sta_list, list) {
 		__sta_info_get(sta);
 		sta_info_cleanup_expire_buffered(local, sta);
 		sta_info_put(sta);
 	}
-	spin_unlock_bh(&local->sta_lock);
+	read_unlock_bh(&local->sta_lock);
 
 	local->sta_cleanup.expires = jiffies + STA_INFO_CLEANUP_INTERVAL;
 	add_timer(&local->sta_cleanup);
@@ -363,35 +343,20 @@ static void sta_info_debugfs_add_task(struct work_struct *work)
 	struct sta_info *sta, *tmp;
 
 	while (1) {
-		spin_lock_bh(&local->sta_lock);
-		if (!list_empty(&local->deleted_sta_list)) {
-			sta = list_entry(local->deleted_sta_list.next,
-					 struct sta_info, list);
-			list_del(local->deleted_sta_list.next);
-		} else
-			sta = NULL;
-		spin_unlock_bh(&local->sta_lock);
-		if (!sta)
-			break;
-		finish_sta_info_free(local, sta);
-	}
-
-	while (1) {
 		sta = NULL;
-		spin_lock_bh(&local->sta_lock);
+		read_lock_bh(&local->sta_lock);
 		list_for_each_entry(tmp, &local->sta_list, list) {
-			if (!tmp->debugfs_registered) {
+			if (!tmp->debugfs.dir) {
 				sta = tmp;
 				__sta_info_get(sta);
 				break;
 			}
 		}
-		spin_unlock_bh(&local->sta_lock);
+		read_unlock_bh(&local->sta_lock);
 
 		if (!sta)
 			break;
 
-		sta->debugfs_registered = 1;
 		ieee80211_sta_debugfs_add(sta);
 		rate_control_add_sta_debugfs(sta);
 		sta_info_put(sta);
@@ -401,9 +366,8 @@ static void sta_info_debugfs_add_task(struct work_struct *work)
 
 void sta_info_init(struct ieee80211_local *local)
 {
-	spin_lock_init(&local->sta_lock);
+	rwlock_init(&local->sta_lock);
 	INIT_LIST_HEAD(&local->sta_list);
-	INIT_LIST_HEAD(&local->deleted_sta_list);
 
 	init_timer(&local->sta_cleanup);
 	local->sta_cleanup.expires = jiffies + STA_INFO_CLEANUP_INTERVAL;
@@ -423,17 +387,8 @@ int sta_info_start(struct ieee80211_local *local)
 
 void sta_info_stop(struct ieee80211_local *local)
 {
-	struct sta_info *sta, *tmp;
-
 	del_timer(&local->sta_cleanup);
-
-	list_for_each_entry_safe(sta, tmp, &local->sta_list, list) {
-		/* sta_info_free must be called with 0 as the last
-		 * parameter to ensure all debugfs sta entries are
-		 * unregistered. We don't need locking at this
-		 * point. */
-		sta_info_free(sta, 0);
-	}
+	sta_info_flush(local, NULL);
 }
 
 void sta_info_remove_aid_ptr(struct sta_info *sta)
@@ -461,10 +416,19 @@ void sta_info_remove_aid_ptr(struct sta_info *sta)
 void sta_info_flush(struct ieee80211_local *local, struct net_device *dev)
 {
 	struct sta_info *sta, *tmp;
+	LIST_HEAD(tmp_list);
 
-	spin_lock_bh(&local->sta_lock);
+	write_lock_bh(&local->sta_lock);
 	list_for_each_entry_safe(sta, tmp, &local->sta_list, list)
-		if (!dev || dev == sta->dev)
-			sta_info_free(sta, 1);
-	spin_unlock_bh(&local->sta_lock);
+		if (!dev || dev == sta->dev) {
+			__sta_info_get(sta);
+			sta_info_remove(sta);
+			list_add_tail(&sta->list, &tmp_list);
+		}
+	write_unlock_bh(&local->sta_lock);
+
+	list_for_each_entry_safe(sta, tmp, &tmp_list, list) {
+		sta_info_free(sta);
+		sta_info_put(sta);
+	}
 }