[PATCH v3 07/12] ath11k: add branch predictors in process_rx

[P Praneesh]

In datapath, add branch predictors where required in the process rx().
This protects high value rx path without having performance overhead.
Also while processing rx packets, the pointer that is returned by
rcu_dereference() is not dereferenced. so it is preferable to use
rcu_access_pointer() here.

Tested-on: QCN9074 hw1.0 PCI WLAN.HK.2.4.0.1.r2-00012-QCAHKSWPL_SILICONZ-1
Tested-on: IPQ8074 hw2.0 AHB WLAN.HK.2.4.0.1-01695-QCAHKSWPL_SILICONZ-1

Co-developed-by: Sriram R <srirrama at codeaurora.org>
Signed-off-by: Sriram R <srirrama at codeaurora.org>
Signed-off-by: Jouni Malinen <jouni at codeaurora.org>
Signed-off-by: P Praneesh <ppranees at codeaurora.org>
---
 drivers/net/wireless/ath/ath11k/dp_rx.c | 24 +++++++++---------------
 1 file changed, 9 insertions(+), 15 deletions(-)

diff --git a/drivers/net/wireless/ath/ath11k/dp_rx.c b/drivers/net/wireless/ath/ath11k/dp_rx.c
index e105bdc..a362615 100644
--- a/drivers/net/wireless/ath/ath11k/dp_rx.c
+++ b/drivers/net/wireless/ath/ath11k/dp_rx.c
@@ -2532,24 +2532,20 @@ static void ath11k_dp_rx_process_received_packets(struct ath11k_base *ab,
 	if (skb_queue_empty(msdu_list))
 		return;
 
-	rcu_read_lock();
-
-	ar = ab->pdevs[mac_id].ar;
-	if (!rcu_dereference(ab->pdevs_active[mac_id])) {
+	if (unlikely(!rcu_access_pointer(ab->pdevs_active[mac_id]))) {
 		__skb_queue_purge(msdu_list);
-		rcu_read_unlock();
 		return;
 	}
 
-	if (test_bit(ATH11K_CAC_RUNNING, &ar->dev_flags)) {
+	ar = ab->pdevs[mac_id].ar;
+	if (unlikely(test_bit(ATH11K_CAC_RUNNING, &ar->dev_flags))) {
 		__skb_queue_purge(msdu_list);
-		rcu_read_unlock();
 		return;
 	}
 
 	while ((msdu = __skb_dequeue(msdu_list))) {
 		ret = ath11k_dp_rx_process_msdu(ar, msdu, msdu_list);
-		if (ret) {
+		if (unlikely(ret)) {
 			ath11k_dbg(ab, ATH11K_DBG_DATA,
 				   "Unable to process msdu %d", ret);
 			dev_kfree_skb_any(msdu);
@@ -2558,8 +2554,6 @@ static void ath11k_dp_rx_process_received_packets(struct ath11k_base *ab,
 
 		ath11k_dp_rx_deliver_msdu(ar, napi, msdu);
 	}
-
-	rcu_read_unlock();
 }
 
 int ath11k_dp_process_rx(struct ath11k_base *ab, int ring_id,
@@ -2604,7 +2598,7 @@ int ath11k_dp_process_rx(struct ath11k_base *ab, int ring_id,
 		rx_ring = &ar->dp.rx_refill_buf_ring;
 		spin_lock_bh(&rx_ring->idr_lock);
 		msdu = idr_find(&rx_ring->bufs_idr, buf_id);
-		if (!msdu) {
+		if (unlikely(!msdu)) {
 			ath11k_warn(ab, "frame rx with invalid buf_id %d\n",
 				    buf_id);
 			spin_unlock_bh(&rx_ring->idr_lock);
@@ -2623,8 +2617,8 @@ int ath11k_dp_process_rx(struct ath11k_base *ab, int ring_id,
 
 		push_reason = FIELD_GET(HAL_REO_DEST_RING_INFO0_PUSH_REASON,
 					desc->info0);
-		if (push_reason !=
-		    HAL_REO_DEST_RING_PUSH_REASON_ROUTING_INSTRUCTION) {
+		if (unlikely(push_reason !=
+			     HAL_REO_DEST_RING_PUSH_REASON_ROUTING_INSTRUCTION)) {
 			dev_kfree_skb_any(msdu);
 			ab->soc_stats.hal_reo_error[dp->reo_dst_ring[ring_id].ring_id]++;
 			continue;
@@ -2659,7 +2653,7 @@ int ath11k_dp_process_rx(struct ath11k_base *ab, int ring_id,
 	 * head pointer so that we can reap complete MPDU in the current
 	 * rx processing.
 	 */
-	if (!done && ath11k_hal_srng_dst_num_free(ab, srng, true)) {
+	if (unlikely(!done && ath11k_hal_srng_dst_num_free(ab, srng, true))) {
 		ath11k_hal_srng_access_end(ab, srng);
 		goto try_again;
 	}
@@ -2668,7 +2662,7 @@ int ath11k_dp_process_rx(struct ath11k_base *ab, int ring_id,
 
 	spin_unlock_bh(&srng->lock);
 
-	if (!total_msdu_reaped)
+	if (unlikely(!total_msdu_reaped))
 		goto exit;
 
 	for (i = 0; i < ab->num_radios; i++) {
-- 
2.7.4