mac80211: reduce station management complexity

Now that IBSS no longer needs to insert stations
from atomic context, we can get rid of all the
special cases for that, and even get rid of the
sta_lock (though it needs to stay as tim_lock.)

This makes the station management code much more
straight-forward.

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

net/mac80211/ieee80211_i.h

@@ -855,18 +855,15 @@ struct ieee80211_local {
 
 	/* Station data */
 	/*
-	 * The mutex only protects the list and counter,
-	 * reads are done in RCU.
-	 * Additionally, the lock protects the hash table,
-	 * the pending list and each BSS's TIM bitmap.
+	 * The mutex only protects the list, hash table and
+	 * counter, reads are done with RCU.
 	 */
 	struct mutex sta_mtx;
-	spinlock_t sta_lock;
+	spinlock_t tim_lock;
 	unsigned long num_sta;
-	struct list_head sta_list, sta_pending_list;
+	struct list_head sta_list;
 	struct sta_info __rcu *sta_hash[STA_HASH_SIZE];
 	struct timer_list sta_cleanup;
-	struct work_struct sta_finish_work;
 	int sta_generation;
 
 	struct sk_buff_head pending[IEEE80211_MAX_QUEUES];

net/mac80211/sta_info.c

@@ -62,14 +62,14 @@
  * freed before they are done using it.
  */
 
-/* Caller must hold local->sta_lock */
+/* Caller must hold local->sta_mtx */
 static int sta_info_hash_del(struct ieee80211_local *local,
 			     struct sta_info *sta)
 {
 	struct sta_info *s;
 
 	s = rcu_dereference_protected(local->sta_hash[STA_HASH(sta->sta.addr)],
-				      lockdep_is_held(&local->sta_lock));
+				      lockdep_is_held(&local->sta_mtx));
 	if (!s)
 		return -ENOENT;
 	if (s == sta) {
@@ -81,7 +81,7 @@ static int sta_info_hash_del(struct ieee80211_local *local,
 	while (rcu_access_pointer(s->hnext) &&
 	       rcu_access_pointer(s->hnext) != sta)
 		s = rcu_dereference_protected(s->hnext,
-					lockdep_is_held(&local->sta_lock));
+					lockdep_is_held(&local->sta_mtx));
 	if (rcu_access_pointer(s->hnext)) {
 		RCU_INIT_POINTER(s->hnext, sta->hnext);
 		return 0;
@@ -98,14 +98,12 @@ struct sta_info *sta_info_get(struct ieee80211_sub_if_data *sdata,
 	struct sta_info *sta;
 
 	sta = rcu_dereference_check(local->sta_hash[STA_HASH(addr)],
-				    lockdep_is_held(&local->sta_lock) ||
 				    lockdep_is_held(&local->sta_mtx));
 	while (sta) {
 		if (sta->sdata == sdata && !sta->dummy &&
 		    memcmp(sta->sta.addr, addr, ETH_ALEN) == 0)
 			break;
 		sta = rcu_dereference_check(sta->hnext,
-					    lockdep_is_held(&local->sta_lock) ||
 					    lockdep_is_held(&local->sta_mtx));
 	}
 	return sta;
@@ -119,14 +117,12 @@ struct sta_info *sta_info_get_rx(struct ieee80211_sub_if_data *sdata,
 	struct sta_info *sta;
 
 	sta = rcu_dereference_check(local->sta_hash[STA_HASH(addr)],
-				    lockdep_is_held(&local->sta_lock) ||
 				    lockdep_is_held(&local->sta_mtx));
 	while (sta) {
 		if (sta->sdata == sdata &&
 		    memcmp(sta->sta.addr, addr, ETH_ALEN) == 0)
 			break;
 		sta = rcu_dereference_check(sta->hnext,
-					    lockdep_is_held(&local->sta_lock) ||
 					    lockdep_is_held(&local->sta_mtx));
 	}
 	return sta;
@@ -143,7 +139,6 @@ struct sta_info *sta_info_get_bss(struct ieee80211_sub_if_data *sdata,
 	struct sta_info *sta;
 
 	sta = rcu_dereference_check(local->sta_hash[STA_HASH(addr)],
-				    lockdep_is_held(&local->sta_lock) ||
 				    lockdep_is_held(&local->sta_mtx));
 	while (sta) {
 		if ((sta->sdata == sdata ||
@@ -152,7 +147,6 @@ struct sta_info *sta_info_get_bss(struct ieee80211_sub_if_data *sdata,
 		    memcmp(sta->sta.addr, addr, ETH_ALEN) == 0)
 			break;
 		sta = rcu_dereference_check(sta->hnext,
-					    lockdep_is_held(&local->sta_lock) ||
 					    lockdep_is_held(&local->sta_mtx));
 	}
 	return sta;
@@ -169,7 +163,6 @@ struct sta_info *sta_info_get_bss_rx(struct ieee80211_sub_if_data *sdata,
 	struct sta_info *sta;
 
 	sta = rcu_dereference_check(local->sta_hash[STA_HASH(addr)],
-				    lockdep_is_held(&local->sta_lock) ||
 				    lockdep_is_held(&local->sta_mtx));
 	while (sta) {
 		if ((sta->sdata == sdata ||
@@ -177,7 +170,6 @@ struct sta_info *sta_info_get_bss_rx(struct ieee80211_sub_if_data *sdata,
 		    memcmp(sta->sta.addr, addr, ETH_ALEN) == 0)
 			break;
 		sta = rcu_dereference_check(sta->hnext,
-					    lockdep_is_held(&local->sta_lock) ||
 					    lockdep_is_held(&local->sta_mtx));
 	}
 	return sta;
@@ -228,10 +220,11 @@ void sta_info_free(struct ieee80211_local *local, struct sta_info *sta)
 	kfree(sta);
 }
 
-/* Caller must hold local->sta_lock */
+/* Caller must hold local->sta_mtx */
 static void sta_info_hash_add(struct ieee80211_local *local,
 			      struct sta_info *sta)
 {
+	lockdep_assert_held(&local->sta_mtx);
 	sta->hnext = local->sta_hash[STA_HASH(sta->sta.addr)];
 	RCU_INIT_POINTER(local->sta_hash[STA_HASH(sta->sta.addr)], sta);
 }
@@ -339,89 +332,6 @@ struct sta_info *sta_info_alloc(struct ieee80211_sub_if_data *sdata,
 	return sta;
 }
 
-static int sta_info_finish_insert(struct sta_info *sta,
-				bool async, bool dummy_reinsert)
-{
-	struct ieee80211_local *local = sta->local;
-	struct ieee80211_sub_if_data *sdata = sta->sdata;
-	struct station_info sinfo;
-	unsigned long flags;
-	int err = 0;
-
-	lockdep_assert_held(&local->sta_mtx);
-
-	if (!sta->dummy || dummy_reinsert) {
-		/* notify driver */
-		err = drv_sta_add(local, sdata, &sta->sta);
-		if (err) {
-			if (sdata->vif.type != NL80211_IFTYPE_ADHOC)
-				return err;
-			printk(KERN_DEBUG "%s: failed to add IBSS STA %pM to "
-					  "driver (%d) - keeping it anyway.\n",
-			       sdata->name, sta->sta.addr, err);
-		} else
-			sta->uploaded = true;
-
-		sdata = sta->sdata;
-	}
-
-	if (!dummy_reinsert) {
-		local->num_sta++;
-		local->sta_generation++;
-		smp_mb();
-
-		/* make the station visible */
-		spin_lock_irqsave(&local->sta_lock, flags);
-		sta_info_hash_add(local, sta);
-		spin_unlock_irqrestore(&local->sta_lock, flags);
-
-		list_add(&sta->list, &local->sta_list);
-	} else {
-		sta->dummy = false;
-	}
-
-	if (!sta->dummy) {
-		ieee80211_sta_debugfs_add(sta);
-		rate_control_add_sta_debugfs(sta);
-
-		memset(&sinfo, 0, sizeof(sinfo));
-		sinfo.filled = 0;
-		sinfo.generation = local->sta_generation;
-		cfg80211_new_sta(sdata->dev, sta->sta.addr, &sinfo, GFP_KERNEL);
-	}
-
-	return 0;
-}
-
-static void sta_info_finish_pending(struct ieee80211_local *local)
-{
-	struct sta_info *sta;
-	unsigned long flags;
-
-	spin_lock_irqsave(&local->sta_lock, flags);
-	while (!list_empty(&local->sta_pending_list)) {
-		sta = list_first_entry(&local->sta_pending_list,
-				       struct sta_info, list);
-		list_del(&sta->list);
-		spin_unlock_irqrestore(&local->sta_lock, flags);
-
-		sta_info_finish_insert(sta, true, false);
-
-		spin_lock_irqsave(&local->sta_lock, flags);
-	}
-	spin_unlock_irqrestore(&local->sta_lock, flags);
-}
-
-static void sta_info_finish_work(struct work_struct *work)
-{
-	struct ieee80211_local *local =
-		container_of(work, struct ieee80211_local, sta_finish_work);
-
-	mutex_lock(&local->sta_mtx);
-	sta_info_finish_pending(local);
-	mutex_unlock(&local->sta_mtx);
-}
-
 static int sta_info_insert_check(struct sta_info *sta)
 {
 	struct ieee80211_sub_if_data *sdata = sta->sdata;
@@ -441,70 +351,24 @@ static int sta_info_insert_check(struct sta_info *sta)
 	return 0;
 }
 
-static int sta_info_insert_ibss(struct sta_info *sta) __acquires(RCU)
-{
-	struct ieee80211_local *local = sta->local;
-	struct ieee80211_sub_if_data *sdata = sta->sdata;
-	unsigned long flags;
-
-	spin_lock_irqsave(&local->sta_lock, flags);
-	/* check if STA exists already */
-	if (sta_info_get_bss_rx(sdata, sta->sta.addr)) {
-		spin_unlock_irqrestore(&local->sta_lock, flags);
-		rcu_read_lock();
-		return -EEXIST;
-	}
-
-	local->num_sta++;
-	local->sta_generation++;
-	smp_mb();
-	sta_info_hash_add(local, sta);
-
-	list_add_tail(&sta->list, &local->sta_pending_list);
-
-	rcu_read_lock();
-	spin_unlock_irqrestore(&local->sta_lock, flags);
-
-#ifdef CONFIG_MAC80211_VERBOSE_DEBUG
-	wiphy_debug(local->hw.wiphy, "Added IBSS STA %pM\n",
-			sta->sta.addr);
-#endif /* CONFIG_MAC80211_VERBOSE_DEBUG */
-
-	ieee80211_queue_work(&local->hw, &local->sta_finish_work);
-
-	return 0;
-}
-
 /*
  * should be called with sta_mtx locked
  * this function replaces the mutex lock
  * with a RCU lock
  */
-static int sta_info_insert_non_ibss(struct sta_info *sta) __acquires(RCU)
+static int sta_info_insert_finish(struct sta_info *sta) __acquires(RCU)
 {
 	struct ieee80211_local *local = sta->local;
 	struct ieee80211_sub_if_data *sdata = sta->sdata;
-	unsigned long flags;
 	struct sta_info *exist_sta;
 	bool dummy_reinsert = false;
 	int err = 0;
 
 	lockdep_assert_held(&local->sta_mtx);
 
-	/*
-	 * On first glance, this will look racy, because the code
-	 * in this function, which inserts a station with sleeping,
-	 * unlocks the sta_lock between checking existence in the
-	 * hash table and inserting into it.
-	 *
-	 * However, it is not racy against itself because it keeps
-	 * the mutex locked.
-	 */
-
-	spin_lock_irqsave(&local->sta_lock, flags);
 	/*
 	 * check if STA exists already.
-	 * only accept a scenario of a second call to sta_info_insert_non_ibss
+	 * only accept a scenario of a second call to sta_info_insert_finish
 	 * with a dummy station entry that was inserted earlier
 	 * in that case - assume that the dummy station flag should
 	 * be removed.
@@ -514,20 +378,47 @@ static int sta_info_insert_non_ibss(struct sta_info *sta) __acquires(RCU)
 		if (exist_sta == sta && sta->dummy) {
 			dummy_reinsert = true;
 		} else {
-			spin_unlock_irqrestore(&local->sta_lock, flags);
-			mutex_unlock(&local->sta_mtx);
-			rcu_read_lock();
-			return -EEXIST;
+			err = -EEXIST;
+			goto out_err;
 		}
 	}
 
-	spin_unlock_irqrestore(&local->sta_lock, flags);
+	if (!sta->dummy || dummy_reinsert) {
+		/* notify driver */
+		err = drv_sta_add(local, sdata, &sta->sta);
+		if (err) {
+			if (sdata->vif.type != NL80211_IFTYPE_ADHOC)
+				goto out_err;
+			printk(KERN_DEBUG "%s: failed to add IBSS STA %pM to "
+					  "driver (%d) - keeping it anyway.\n",
+			       sdata->name, sta->sta.addr, err);
+		} else
+			sta->uploaded = true;
+	}
 
-	err = sta_info_finish_insert(sta, false, dummy_reinsert);
-	if (err) {
-		mutex_unlock(&local->sta_mtx);
-		rcu_read_lock();
-		return err;
+	if (!dummy_reinsert) {
+		local->num_sta++;
+		local->sta_generation++;
+		smp_mb();
+
+		/* make the station visible */
+		sta_info_hash_add(local, sta);
+
+		list_add(&sta->list, &local->sta_list);
+	} else {
+		sta->dummy = false;
+	}
+
+	if (!sta->dummy) {
+		struct station_info sinfo;
+
+		ieee80211_sta_debugfs_add(sta);
+		rate_control_add_sta_debugfs(sta);
+
+		memset(&sinfo, 0, sizeof(sinfo));
+		sinfo.filled = 0;
+		sinfo.generation = local->sta_generation;
+		cfg80211_new_sta(sdata->dev, sta->sta.addr, &sinfo, GFP_KERNEL);
 	}
 
 #ifdef CONFIG_MAC80211_VERBOSE_DEBUG
@@ -543,47 +434,28 @@ static int sta_info_insert_non_ibss(struct sta_info *sta) __acquires(RCU)
 		mesh_accept_plinks_update(sdata);
 
 	return 0;
+ out_err:
+	mutex_unlock(&local->sta_mtx);
+	rcu_read_lock();
+	return err;
 }
 
 int sta_info_insert_rcu(struct sta_info *sta) __acquires(RCU)
 {
 	struct ieee80211_local *local = sta->local;
-	struct ieee80211_sub_if_data *sdata = sta->sdata;
 	int err = 0;
 
+	might_sleep();
+
 	err = sta_info_insert_check(sta);
 	if (err) {
 		rcu_read_lock();
 		goto out_free;
 	}
 
-	/*
-	 * In ad-hoc mode, we sometimes need to insert stations
-	 * from tasklet context from the RX path. To avoid races,
-	 * always do so in that case -- see the comment below.
-	 */
-	if (sdata->vif.type == NL80211_IFTYPE_ADHOC) {
-		err = sta_info_insert_ibss(sta);
-		if (err)
-			goto out_free;
-
-		return 0;
-	}
-
-	/*
-	 * It might seem that the function called below is in race against
-	 * the function call above that atomically inserts the station... That,
-	 * however, is not true because the above code can only
-	 * be invoked for IBSS interfaces, and the below code will
-	 * not be -- and the two do not race against each other as
-	 * the hash table also keys off the interface.
-	 */
-
-	might_sleep();
-
 	mutex_lock(&local->sta_mtx);
 
-	err = sta_info_insert_non_ibss(sta);
+	err = sta_info_insert_finish(sta);
 	if (err)
 		goto out_free;
 
@@ -617,7 +489,7 @@ int sta_info_reinsert(struct sta_info *sta)
 
 	might_sleep();
 
-	err = sta_info_insert_non_ibss(sta);
+	err = sta_info_insert_finish(sta);
 	rcu_read_unlock();
 	return err;
 }
@@ -704,7 +576,7 @@ void sta_info_recalc_tim(struct sta_info *sta)
 	}
 
  done:
-	spin_lock_irqsave(&local->sta_lock, flags);
+	spin_lock_irqsave(&local->tim_lock, flags);
 
 	if (indicate_tim)
 		__bss_tim_set(bss, sta->sta.aid);
@@ -717,7 +589,7 @@ void sta_info_recalc_tim(struct sta_info *sta)
 		local->tim_in_locked_section = false;
 	}
 
-	spin_unlock_irqrestore(&local->sta_lock, flags);
+	spin_unlock_irqrestore(&local->tim_lock, flags);
 }
 
 static bool sta_info_buffer_expired(struct sta_info *sta, struct sk_buff *skb)
@@ -841,7 +713,6 @@ static int __must_check __sta_info_destroy(struct sta_info *sta)
 {
 	struct ieee80211_local *local;
 	struct ieee80211_sub_if_data *sdata;
-	unsigned long flags;
 	int ret, i, ac;
 	struct tid_ampdu_tx *tid_tx;
 
@@ -862,15 +733,12 @@ static int __must_check __sta_info_destroy(struct sta_info *sta)
 	set_sta_flag(sta, WLAN_STA_BLOCK_BA);
 	ieee80211_sta_tear_down_BA_sessions(sta, true);
 
-	spin_lock_irqsave(&local->sta_lock, flags);
 	ret = sta_info_hash_del(local, sta);
-	/* this might still be the pending list ... which is fine */
-	if (!ret)
-		list_del(&sta->list);
-	spin_unlock_irqrestore(&local->sta_lock, flags);
 	if (ret)
 		return ret;
 
+	list_del(&sta->list);
+
 	mutex_lock(&local->key_mtx);
 	for (i = 0; i < NUM_DEFAULT_KEYS; i++)
 		__ieee80211_key_free(key_mtx_dereference(local, sta->gtk[i]));
@@ -1025,11 +893,9 @@ static void sta_info_cleanup(unsigned long data)
 
 void sta_info_init(struct ieee80211_local *local)
 {
-	spin_lock_init(&local->sta_lock);
+	spin_lock_init(&local->tim_lock);
 	mutex_init(&local->sta_mtx);
 	INIT_LIST_HEAD(&local->sta_list);
-	INIT_LIST_HEAD(&local->sta_pending_list);
-	INIT_WORK(&local->sta_finish_work, sta_info_finish_work);
 
 	setup_timer(&local->sta_cleanup, sta_info_cleanup,
 		    (unsigned long)local);
@@ -1058,9 +924,6 @@ int sta_info_flush(struct ieee80211_local *local,
 	might_sleep();
 
 	mutex_lock(&local->sta_mtx);
-
-	sta_info_finish_pending(local);
-
 	list_for_each_entry_safe(sta, tmp, &local->sta_list, list) {
 		if (!sdata || sdata == sta->sdata)
 			WARN_ON(__sta_info_destroy(sta));

net/mac80211/tx.c

@@ -2333,9 +2333,9 @@ struct sk_buff *ieee80211_beacon_get_tim(struct ieee80211_hw *hw,
 			} else {
 				unsigned long flags;
 
-				spin_lock_irqsave(&local->sta_lock, flags);
+				spin_lock_irqsave(&local->tim_lock, flags);
 				ieee80211_beacon_add_tim(ap, skb, beacon);
-				spin_unlock_irqrestore(&local->sta_lock, flags);
+				spin_unlock_irqrestore(&local->tim_lock, flags);
 			}
 
 			if (tim_offset)