netdev - [PATCH net-next 2/3] xsk: add the atomic parameter around cq in generic path

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Message-Id: <20251124080858.89593-3-kerneljasonxing@gmail.com>
Date: Mon, 24 Nov 2025 16:08:57 +0800
From: Jason Xing <kerneljasonxing@...il.com>
To: davem@...emloft.net,
	edumazet@...gle.com,
	kuba@...nel.org,
	pabeni@...hat.com,
	bjorn@...nel.org,
	magnus.karlsson@...el.com,
	maciej.fijalkowski@...el.com,
	jonathan.lemon@...il.com,
	sdf@...ichev.me,
	ast@...nel.org,
	daniel@...earbox.net,
	hawk@...nel.org,
	john.fastabend@...il.com
Cc: bpf@...r.kernel.org,
	netdev@...r.kernel.org,
	Jason Xing <kernelxing@...cent.com>
Subject: [PATCH net-next 2/3] xsk: add the atomic parameter around cq in generic path

From: Jason Xing <kernelxing@...cent.com>

No functional changes here. Add a new parameter as a prep to help
completion queue in copy mode convert into atomic type in the rest of
this series. The patch also keeps the unified interface.

Signed-off-by: Jason Xing <kernelxing@...cent.com>
---
 net/xdp/xsk.c       |  8 ++++----
 net/xdp/xsk_queue.h | 31 +++++++++++++++++++------------
 2 files changed, 23 insertions(+), 16 deletions(-)

diff --git a/net/xdp/xsk.c b/net/xdp/xsk.c
index bcfd400e9cf8..4e95b894f218 100644
--- a/net/xdp/xsk.c
+++ b/net/xdp/xsk.c
@@ -276,7 +276,7 @@ static int __xsk_rcv(struct xdp_sock *xs, struct xdp_buff *xdp, u32 len)
 		xs->rx_dropped++;
 		return -ENOMEM;
 	}
-	if (xskq_prod_nb_free(xs->rx, num_desc) < num_desc) {
+	if (xskq_prod_nb_free(xs->rx, num_desc, false) < num_desc) {
 		xs->rx_queue_full++;
 		return -ENOBUFS;
 	}
@@ -519,7 +519,7 @@ u32 xsk_tx_peek_release_desc_batch(struct xsk_buff_pool *pool, u32 nb_pkts)
 	 * packets. This avoids having to implement any buffering in
 	 * the Tx path.
 	 */
-	nb_pkts = xskq_prod_nb_free(pool->cq, nb_pkts);
+	nb_pkts = xskq_prod_nb_free(pool->cq, nb_pkts, false);
 	if (!nb_pkts)
 		goto out;
 
@@ -551,7 +551,7 @@ static int xsk_cq_reserve_locked(struct xsk_buff_pool *pool)
 	int ret;
 
 	spin_lock(&pool->cq_cached_prod_lock);
-	ret = xskq_prod_reserve(pool->cq);
+	ret = xskq_prod_reserve(pool->cq, false);
 	spin_unlock(&pool->cq_cached_prod_lock);
 
 	return ret;
@@ -588,7 +588,7 @@ static void xsk_cq_submit_addr_locked(struct xsk_buff_pool *pool,
 static void xsk_cq_cancel_locked(struct xsk_buff_pool *pool, u32 n)
 {
 	spin_lock(&pool->cq_cached_prod_lock);
-	xskq_prod_cancel_n(pool->cq, n);
+	xskq_prod_cancel_n(pool->cq, n, false);
 	spin_unlock(&pool->cq_cached_prod_lock);
 }
 
diff --git a/net/xdp/xsk_queue.h b/net/xdp/xsk_queue.h
index 44cc01555c0b..7b4d9b954584 100644
--- a/net/xdp/xsk_queue.h
+++ b/net/xdp/xsk_queue.h
@@ -378,37 +378,44 @@ static inline u32 xskq_get_prod(struct xsk_queue *q)
 	return READ_ONCE(q->ring->producer);
 }
 
-static inline u32 xskq_prod_nb_free(struct xsk_queue *q, u32 max)
+static inline u32 xskq_prod_nb_free(struct xsk_queue *q, u32 max, bool atomic)
 {
-	u32 free_entries = q->nentries - (q->cached_prod - q->cached_cons);
+	u32 cached_prod = atomic ? atomic_read(&q->cached_prod_atomic) : q->cached_prod;
+	u32 free_entries = q->nentries - (cached_prod - q->cached_cons);
 
 	if (free_entries >= max)
 		return max;
 
 	/* Refresh the local tail pointer */
 	q->cached_cons = READ_ONCE(q->ring->consumer);
-	free_entries = q->nentries - (q->cached_prod - q->cached_cons);
+	free_entries = q->nentries - (cached_prod - q->cached_cons);
 
 	return free_entries >= max ? max : free_entries;
 }
 
-static inline bool xskq_prod_is_full(struct xsk_queue *q)
+static inline bool xskq_prod_is_full(struct xsk_queue *q, bool atomic)
 {
-	return xskq_prod_nb_free(q, 1) ? false : true;
+	return xskq_prod_nb_free(q, 1, atomic) ? false : true;
 }
 
-static inline void xskq_prod_cancel_n(struct xsk_queue *q, u32 cnt)
+static inline void xskq_prod_cancel_n(struct xsk_queue *q, u32 cnt, bool atomic)
 {
-	q->cached_prod -= cnt;
+	if (atomic)
+		atomic_sub(cnt, &q->cached_prod_atomic);
+	else
+		q->cached_prod -= cnt;
 }
 
-static inline int xskq_prod_reserve(struct xsk_queue *q)
+static inline int xskq_prod_reserve(struct xsk_queue *q, bool atomic)
 {
-	if (xskq_prod_is_full(q))
+	if (xskq_prod_is_full(q, atomic))
 		return -ENOSPC;
 
 	/* A, matches D */
-	q->cached_prod++;
+	if (atomic)
+		atomic_inc(&q->cached_prod_atomic);
+	else
+		q->cached_prod++;
 	return 0;
 }
 
@@ -416,7 +423,7 @@ static inline int xskq_prod_reserve_addr(struct xsk_queue *q, u64 addr)
 {
 	struct xdp_umem_ring *ring = (struct xdp_umem_ring *)q->ring;
 
-	if (xskq_prod_is_full(q))
+	if (xskq_prod_is_full(q, false))
 		return -ENOSPC;
 
 	/* A, matches D */
@@ -450,7 +457,7 @@ static inline int xskq_prod_reserve_desc(struct xsk_queue *q,
 	struct xdp_rxtx_ring *ring = (struct xdp_rxtx_ring *)q->ring;
 	u32 idx;
 
-	if (xskq_prod_is_full(q))
+	if (xskq_prod_is_full(q, false))
 		return -ENOBUFS;
 
 	/* A, matches D */
-- 
2.41.3