[PATCH 12/12] ath11k: avoid unnecessary lock contention in tx_completion path

[Jouni Malinen]

From: P Praneesh <ppranees at codeaurora.org>

Lock is not needed for the readable idr operation, so avoid spin_lock_bh
for the idr_find() call. No need to disable the bottom half preempt if
it is already in bottom half context, so modify the spin_lock_bh to
spin_lock in the data tx completion handler.

Tested-on: IPQ8074 hw2.0 AHB WLAN.HK.2.4.0.1-01734-QCAHKSWPL_SILICONZ-1 v2

Co-developed-by: Karthikeyan Periyasamy <periyasa at codeaurora.org>
Signed-off-by: Karthikeyan Periyasamy <periyasa at codeaurora.org>
Signed-off-by: P Praneesh <ppranees at codeaurora.org>
Signed-off-by: Jouni Malinen <jouni at codeaurora.org>
---
 drivers/net/wireless/ath/ath11k/dp_tx.c | 18 ++++++++----------
 1 file changed, 8 insertions(+), 10 deletions(-)

diff --git a/drivers/net/wireless/ath/ath11k/dp_tx.c b/drivers/net/wireless/ath/ath11k/dp_tx.c
index ab9ccf0eb274..659f9d98bc0c 100644
--- a/drivers/net/wireless/ath/ath11k/dp_tx.c
+++ b/drivers/net/wireless/ath/ath11k/dp_tx.c
@@ -288,19 +288,18 @@ static void ath11k_dp_tx_free_txbuf(struct ath11k_base *ab, u8 mac_id,
 	struct sk_buff *msdu;
 	struct ath11k_skb_cb *skb_cb;
 
-	spin_lock_bh(&tx_ring->tx_idr_lock);
 	msdu = idr_find(&tx_ring->txbuf_idr, msdu_id);
-	if (!msdu) {
+	if (unlikely(!msdu)) {
 		ath11k_warn(ab, "tx completion for unknown msdu_id %d\n",
 			    msdu_id);
-		spin_unlock_bh(&tx_ring->tx_idr_lock);
 		return;
 	}
 
 	skb_cb = ATH11K_SKB_CB(msdu);
 
+	spin_lock(&tx_ring->tx_idr_lock);
 	idr_remove(&tx_ring->txbuf_idr, msdu_id);
-	spin_unlock_bh(&tx_ring->tx_idr_lock);
+	spin_unlock(&tx_ring->tx_idr_lock);
 
 	dma_unmap_single(ab->dev, skb_cb->paddr, msdu->len, DMA_TO_DEVICE);
 	dev_kfree_skb_any(msdu);
@@ -320,12 +319,10 @@ ath11k_dp_tx_htt_tx_complete_buf(struct ath11k_base *ab,
 	struct ath11k_skb_cb *skb_cb;
 	struct ath11k *ar;
 
-	spin_lock_bh(&tx_ring->tx_idr_lock);
 	msdu = idr_find(&tx_ring->txbuf_idr, ts->msdu_id);
 	if (unlikely(!msdu)) {
 		ath11k_warn(ab, "htt tx completion for unknown msdu_id %d\n",
 			    ts->msdu_id);
-		spin_unlock_bh(&tx_ring->tx_idr_lock);
 		return;
 	}
 
@@ -334,8 +331,9 @@ ath11k_dp_tx_htt_tx_complete_buf(struct ath11k_base *ab,
 
 	ar = skb_cb->ar;
 
+	spin_lock(&tx_ring->tx_idr_lock);
 	idr_remove(&tx_ring->txbuf_idr, ts->msdu_id);
-	spin_unlock_bh(&tx_ring->tx_idr_lock);
+	spin_unlock(&tx_ring->tx_idr_lock);
 
 	if (atomic_dec_and_test(&ar->dp.num_tx_pending))
 		wake_up(&ar->dp.tx_empty_waitq);
@@ -584,16 +582,16 @@ void ath11k_dp_tx_completion_handler(struct ath11k_base *ab, int ring_id)
 			continue;
 		}
 
-		spin_lock_bh(&tx_ring->tx_idr_lock);
 		msdu = idr_find(&tx_ring->txbuf_idr, msdu_id);
 		if (unlikely(!msdu)) {
 			ath11k_warn(ab, "tx completion for unknown msdu_id %d\n",
 				    msdu_id);
-			spin_unlock_bh(&tx_ring->tx_idr_lock);
 			continue;
 		}
+
+		spin_lock(&tx_ring->tx_idr_lock);
 		idr_remove(&tx_ring->txbuf_idr, msdu_id);
-		spin_unlock_bh(&tx_ring->tx_idr_lock);
+		spin_unlock(&tx_ring->tx_idr_lock);
 
 		ar = ab->pdevs[mac_id].ar;
 
-- 
2.25.1