From:   Felix Fietkau <nbd@nbd.name>
To:     linux-wireless@vger.kernel.org
Cc:     johannes@sipsolutions.net
Subject: [PATCH 4/5] mac80211: run late dequeue late tx handlers without holding fq->lock
Date:   Sat, 16 Mar 2019 18:06:33 +0100
Message-Id: <20190316170634.13125-4-nbd@nbd.name>
In-Reply-To: <20190316170634.13125-1-nbd@nbd.name>
References: <20190316170634.13125-1-nbd@nbd.name>
Sender: linux-wireless-owner@vger.kernel.org
Precedence: bulk

Reduces lock contention on enqueue/dequeue of iTXQ packets

Signed-off-by: Felix Fietkau <nbd@nbd.name>
---
 net/mac80211/tx.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/net/mac80211/tx.c b/net/mac80211/tx.c
index 8127e43e12b1..f85344c9af62 100644
--- a/net/mac80211/tx.c
+++ b/net/mac80211/tx.c
@@ -3544,6 +3544,7 @@ 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) ||
@@ -3560,11 +3561,12 @@ 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);
 
@@ -3610,8 +3612,11 @@ 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) &&
@@ -3650,6 +3655,7 @@ 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);
-- 
2.17.0