commit ded4698b58cb23c22b0dcbd829ced19ce4e6ce02
author Felix Fietkau <nbd@nbd.name> Sat Mar 16 18:06:33 2019 +0100
committer Johannes Berg <johannes.berg@intel.com> Fri Apr 26 13:02:11 2019 +0200
tree 9a386c23393fb39600f5ed1a5763e7285143502d
parent f2af2df800d3648b1d68e02d5b8a5d77cfee8970

mac80211: run late dequeue late tx handlers without holding fq->lock

Reduces lock contention on enqueue/dequeue of iTXQ packets

Signed-off-by: Felix Fietkau <nbd@nbd.name>
Acked-by: Toke Høiland-Jørgensen <toke@redhat.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

net/mac80211/tx.c

diff --git a/net/mac80211/tx.c b/net/mac80211/tx.c
index 2c0fec8..a3c6053 100644
--- a/net/mac80211/tx.c
+++ b/net/mac80211/tx.c
@@ -3535,6 +3535,7 @@ struct sk_buff *ieee80211_tx_dequeue(struct ieee80211_hw *hw,
 	ieee80211_tx_result r;
 	struct ieee80211_vif *vif = txq->vif;
 
+begin:
 	spin_lock_bh(&fq->lock);
 
 	if (test_bit(IEEE80211_TXQ_STOP, &txqi->flags) ||
@@ -3551,11 +3552,12 @@ struct sk_buff *ieee80211_tx_dequeue(struct ieee80211_hw *hw,
 	if (skb)
 		goto out;
 
-begin:
 	skb = fq_tin_dequeue(fq, tin, fq_tin_dequeue_func);
 	if (!skb)
 		goto out;
 
+	spin_unlock_bh(&fq->lock);
+
 	hdr = (struct ieee80211_hdr *)skb->data;
 	info = IEEE80211_SKB_CB(skb);
 
@@ -3600,8 +3602,11 @@ struct sk_buff *ieee80211_tx_dequeue(struct ieee80211_hw *hw,
 
 		skb = __skb_dequeue(&tx.skbs);
 
-		if (!skb_queue_empty(&tx.skbs))
+		if (!skb_queue_empty(&tx.skbs)) {
+			spin_lock_bh(&fq->lock);
 			skb_queue_splice_tail(&tx.skbs, &txqi->frags);
+			spin_unlock_bh(&fq->lock);
+		}
 	}
 
 	if (skb_has_frag_list(skb) &&
@@ -3640,6 +3645,7 @@ struct sk_buff *ieee80211_tx_dequeue(struct ieee80211_hw *hw,
 	}
 
 	IEEE80211_SKB_CB(skb)->control.vif = vif;
+	return skb;
 
 out:
 	spin_unlock_bh(&fq->lock);