+/*
+ * When multiple aggregation sessions on multiple stations
+ * are being created/destroyed simultaneously, we need to
+ * refcount the global queue stop caused by that in order
+ * to not get into a situation where one of the aggregation
+ * setup or teardown re-enables queues before the other is
+ * ready to handle that.
+ *
+ * These two functions take care of this issue by keeping
+ * a global "agg_queue_stop" refcount.
+ */
+static void __acquires(agg_queue)
+ieee80211_stop_queue_agg(struct ieee80211_local *local, int tid)
+{
+ int queue = ieee80211_ac_from_tid(tid);
+
+ if (atomic_inc_return(&local->agg_queue_stop[queue]) == 1)
+ ieee80211_stop_queue_by_reason(
+ &local->hw, queue,
+ IEEE80211_QUEUE_STOP_REASON_AGGREGATION);
+ __acquire(agg_queue);
+}
+
+static void __releases(agg_queue)
+ieee80211_wake_queue_agg(struct ieee80211_local *local, int tid)
+{
+ int queue = ieee80211_ac_from_tid(tid);
+
+ if (atomic_dec_return(&local->agg_queue_stop[queue]) == 0)
+ ieee80211_wake_queue_by_reason(
+ &local->hw, queue,
+ IEEE80211_QUEUE_STOP_REASON_AGGREGATION);
+ __release(agg_queue);
+}
+
+void ieee80211_tx_ba_session_handle_start(struct sta_info *sta, int tid)
+{
+ struct tid_ampdu_tx *tid_tx = sta->ampdu_mlme.tid_tx[tid];
+ struct ieee80211_local *local = sta->local;
+ struct ieee80211_sub_if_data *sdata = sta->sdata;
+ u16 start_seq_num;
+ int ret;
+
+ lockdep_assert_held(&sta->ampdu_mlme.mtx);
+
+ /*
+ * While we're asking the driver about the aggregation,
+ * stop the AC queue so that we don't have to worry
+ * about frames that came in while we were doing that,
+ * which would require us to put them to the AC pending
+ * afterwards which just makes the code more complex.
+ */
+ ieee80211_stop_queue_agg(local, tid);
+
+ clear_bit(HT_AGG_STATE_WANT_START, &tid_tx->state);
+
+ /*
+ * make sure no packets are being processed to get
+ * valid starting sequence number
+ */
+ synchronize_net();
+
+ start_seq_num = sta->tid_seq[tid] >> 4;
+
+ ret = drv_ampdu_action(local, sdata, IEEE80211_AMPDU_TX_START,
+ &sta->sta, tid, &start_seq_num);
+ if (ret) {
+#ifdef CONFIG_MAC80211_HT_DEBUG
+ printk(KERN_DEBUG "BA request denied - HW unavailable for"
+ " tid %d\n", tid);
+#endif
+ spin_lock_bh(&sta->lock);
+ rcu_assign_pointer(sta->ampdu_mlme.tid_tx[tid], NULL);
+ spin_unlock_bh(&sta->lock);
+
+ ieee80211_wake_queue_agg(local, tid);
+ call_rcu(&tid_tx->rcu_head, kfree_tid_tx);
+ return;
+ }
+
+ /* we can take packets again now */
+ ieee80211_wake_queue_agg(local, tid);
+
+ /* activate the timer for the recipient's addBA response */
+ mod_timer(&tid_tx->addba_resp_timer, jiffies + ADDBA_RESP_INTERVAL);
+#ifdef CONFIG_MAC80211_HT_DEBUG
+ printk(KERN_DEBUG "activated addBA response timer on tid %d\n", tid);
+#endif
+
+ spin_lock_bh(&sta->lock);
+ sta->ampdu_mlme.addba_req_num[tid]++;
+ spin_unlock_bh(&sta->lock);
+
+ /* send AddBA request */
+ ieee80211_send_addba_request(sdata, sta->sta.addr, tid,
+ tid_tx->dialog_token, start_seq_num,
+ 0x40, 5000);
+}
+