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214 lines
7.1 KiB
214 lines
7.1 KiB
From: Felix Fietkau <nbd@nbd.name>
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Date: Wed, 13 Mar 2019 19:09:22 +0100
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Subject: [PATCH] mac80211: rework locking for txq scheduling / airtime
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fairness
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Holding the lock around the entire duration of tx scheduling can create
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some nasty lock contention, especially when processing airtime information
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from the tx status or the rx path.
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Improve locking by only holding the active_txq_lock for lookups / scheduling
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list modifications.
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Signed-off-by: Felix Fietkau <nbd@nbd.name>
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---
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--- a/include/net/mac80211.h
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+++ b/include/net/mac80211.h
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@@ -6069,8 +6069,6 @@ struct sk_buff *ieee80211_tx_dequeue(str
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* @hw: pointer as obtained from ieee80211_alloc_hw()
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* @ac: AC number to return packets from.
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*
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- * Should only be called between calls to ieee80211_txq_schedule_start()
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- * and ieee80211_txq_schedule_end().
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* Returns the next txq if successful, %NULL if no queue is eligible. If a txq
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* is returned, it should be returned with ieee80211_return_txq() after the
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* driver has finished scheduling it.
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@@ -6078,51 +6076,41 @@ struct sk_buff *ieee80211_tx_dequeue(str
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struct ieee80211_txq *ieee80211_next_txq(struct ieee80211_hw *hw, u8 ac);
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/**
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- * ieee80211_return_txq - return a TXQ previously acquired by ieee80211_next_txq()
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- *
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- * @hw: pointer as obtained from ieee80211_alloc_hw()
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- * @txq: pointer obtained from station or virtual interface
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- *
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- * Should only be called between calls to ieee80211_txq_schedule_start()
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- * and ieee80211_txq_schedule_end().
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- */
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-void ieee80211_return_txq(struct ieee80211_hw *hw, struct ieee80211_txq *txq);
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-
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-/**
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- * ieee80211_txq_schedule_start - acquire locks for safe scheduling of an AC
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+ * ieee80211_txq_schedule_start - start new scheduling round for TXQs
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*
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* @hw: pointer as obtained from ieee80211_alloc_hw()
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* @ac: AC number to acquire locks for
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*
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- * Acquire locks needed to schedule TXQs from the given AC. Should be called
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- * before ieee80211_next_txq() or ieee80211_return_txq().
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+ * Should be called before ieee80211_next_txq() or ieee80211_return_txq().
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*/
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-void ieee80211_txq_schedule_start(struct ieee80211_hw *hw, u8 ac)
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- __acquires(txq_lock);
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+void ieee80211_txq_schedule_start(struct ieee80211_hw *hw, u8 ac);
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+
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+/* (deprecated) */
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+static inline void ieee80211_txq_schedule_end(struct ieee80211_hw *hw, u8 ac)
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+{
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+}
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/**
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- * ieee80211_txq_schedule_end - release locks for safe scheduling of an AC
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+ * ieee80211_schedule_txq - schedule a TXQ for transmission
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*
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* @hw: pointer as obtained from ieee80211_alloc_hw()
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- * @ac: AC number to acquire locks for
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+ * @txq: pointer obtained from station or virtual interface
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*
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- * Release locks previously acquired by ieee80211_txq_schedule_end().
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+ * Schedules a TXQ for transmission if it is not already scheduled.
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*/
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-void ieee80211_txq_schedule_end(struct ieee80211_hw *hw, u8 ac)
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- __releases(txq_lock);
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+void ieee80211_schedule_txq(struct ieee80211_hw *hw, struct ieee80211_txq *txq);
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/**
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- * ieee80211_schedule_txq - schedule a TXQ for transmission
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+ * ieee80211_return_txq - return a TXQ previously acquired by ieee80211_next_txq()
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*
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* @hw: pointer as obtained from ieee80211_alloc_hw()
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* @txq: pointer obtained from station or virtual interface
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- *
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- * Schedules a TXQ for transmission if it is not already scheduled. Takes a
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- * lock, which means it must *not* be called between
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- * ieee80211_txq_schedule_start() and ieee80211_txq_schedule_end()
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*/
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-void ieee80211_schedule_txq(struct ieee80211_hw *hw, struct ieee80211_txq *txq)
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- __acquires(txq_lock) __releases(txq_lock);
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+static inline void
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+ieee80211_return_txq(struct ieee80211_hw *hw, struct ieee80211_txq *txq)
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+{
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+ ieee80211_schedule_txq(hw, txq);
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+}
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/**
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* ieee80211_txq_may_transmit - check whether TXQ is allowed to transmit
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--- a/net/mac80211/tx.c
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+++ b/net/mac80211/tx.c
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@@ -3648,16 +3648,17 @@ EXPORT_SYMBOL(ieee80211_tx_dequeue);
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struct ieee80211_txq *ieee80211_next_txq(struct ieee80211_hw *hw, u8 ac)
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{
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struct ieee80211_local *local = hw_to_local(hw);
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+ struct ieee80211_txq *ret = NULL;
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struct txq_info *txqi = NULL;
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- lockdep_assert_held(&local->active_txq_lock[ac]);
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+ spin_lock_bh(&local->active_txq_lock[ac]);
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begin:
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txqi = list_first_entry_or_null(&local->active_txqs[ac],
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struct txq_info,
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schedule_order);
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if (!txqi)
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- return NULL;
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+ goto out;
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if (txqi->txq.sta) {
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struct sta_info *sta = container_of(txqi->txq.sta,
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@@ -3674,21 +3675,25 @@ struct ieee80211_txq *ieee80211_next_txq
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if (txqi->schedule_round == local->schedule_round[ac])
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- return NULL;
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+ goto out;
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list_del_init(&txqi->schedule_order);
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txqi->schedule_round = local->schedule_round[ac];
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- return &txqi->txq;
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+ ret = &txqi->txq;
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+
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+out:
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+ spin_unlock_bh(&local->active_txq_lock[ac]);
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+ return ret;
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}
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EXPORT_SYMBOL(ieee80211_next_txq);
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-void ieee80211_return_txq(struct ieee80211_hw *hw,
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- struct ieee80211_txq *txq)
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+void ieee80211_schedule_txq(struct ieee80211_hw *hw,
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+ struct ieee80211_txq *txq)
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{
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struct ieee80211_local *local = hw_to_local(hw);
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struct txq_info *txqi = to_txq_info(txq);
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- lockdep_assert_held(&local->active_txq_lock[txq->ac]);
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+ spin_lock_bh(&local->active_txq_lock[txq->ac]);
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if (list_empty(&txqi->schedule_order) &&
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(!skb_queue_empty(&txqi->frags) || txqi->tin.backlog_packets)) {
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@@ -3708,18 +3713,7 @@ void ieee80211_return_txq(struct ieee802
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list_add_tail(&txqi->schedule_order,
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&local->active_txqs[txq->ac]);
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}
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-}
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-EXPORT_SYMBOL(ieee80211_return_txq);
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-void ieee80211_schedule_txq(struct ieee80211_hw *hw,
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- struct ieee80211_txq *txq)
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- __acquires(txq_lock) __releases(txq_lock)
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-{
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- struct ieee80211_local *local = hw_to_local(hw);
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- struct txq_info *txqi = to_txq_info(txq);
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-
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- spin_lock_bh(&local->active_txq_lock[txq->ac]);
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- ieee80211_return_txq(hw, txq);
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spin_unlock_bh(&local->active_txq_lock[txq->ac]);
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}
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EXPORT_SYMBOL(ieee80211_schedule_txq);
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@@ -3732,7 +3726,7 @@ bool ieee80211_txq_may_transmit(struct i
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struct sta_info *sta;
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u8 ac = txq->ac;
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- lockdep_assert_held(&local->active_txq_lock[ac]);
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+ spin_lock_bh(&local->active_txq_lock[ac]);
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if (!txqi->txq.sta)
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goto out;
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@@ -3762,34 +3756,27 @@ bool ieee80211_txq_may_transmit(struct i
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sta->airtime[ac].deficit += sta->airtime_weight;
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list_move_tail(&txqi->schedule_order, &local->active_txqs[ac]);
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+ spin_unlock_bh(&local->active_txq_lock[ac]);
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return false;
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out:
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if (!list_empty(&txqi->schedule_order))
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list_del_init(&txqi->schedule_order);
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+ spin_unlock_bh(&local->active_txq_lock[ac]);
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return true;
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}
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EXPORT_SYMBOL(ieee80211_txq_may_transmit);
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void ieee80211_txq_schedule_start(struct ieee80211_hw *hw, u8 ac)
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- __acquires(txq_lock)
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{
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struct ieee80211_local *local = hw_to_local(hw);
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spin_lock_bh(&local->active_txq_lock[ac]);
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local->schedule_round[ac]++;
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-}
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-EXPORT_SYMBOL(ieee80211_txq_schedule_start);
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-
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-void ieee80211_txq_schedule_end(struct ieee80211_hw *hw, u8 ac)
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- __releases(txq_lock)
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-{
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- struct ieee80211_local *local = hw_to_local(hw);
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-
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spin_unlock_bh(&local->active_txq_lock[ac]);
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}
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-EXPORT_SYMBOL(ieee80211_txq_schedule_end);
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+EXPORT_SYMBOL(ieee80211_txq_schedule_start);
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void __ieee80211_subif_start_xmit(struct sk_buff *skb,
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struct net_device *dev,
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