netdev - [PATCH net-next v2 3/3] xsk: remove spin lock protection of cached

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Message-Id: <20251125085431.4039-4-kerneljasonxing@gmail.com>
Date: Tue, 25 Nov 2025 16:54:31 +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 v2 3/3] xsk: remove spin lock protection of cached_prod

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

Remove the spin lock protection along with some functions adjusted.

Now cached_prod is fully converted to atomic, which improves the
performance by around 5% over different platforms.

Signed-off-by: Jason Xing <kernelxing@...cent.com>
---
 include/net/xsk_buff_pool.h |  5 -----
 net/xdp/xsk.c               | 21 ++++-----------------
 net/xdp/xsk_buff_pool.c     |  1 -
 3 files changed, 4 insertions(+), 23 deletions(-)

diff --git a/include/net/xsk_buff_pool.h b/include/net/xsk_buff_pool.h
index 92a2358c6ce3..0b1abdb99c9e 100644
--- a/include/net/xsk_buff_pool.h
+++ b/include/net/xsk_buff_pool.h
@@ -90,11 +90,6 @@ struct xsk_buff_pool {
 	 * destructor callback.
 	 */
 	spinlock_t cq_prod_lock;
-	/* Mutual exclusion of the completion ring in the SKB mode.
-	 * Protect: when sockets share a single cq when the same netdev
-	 * and queue id is shared.
-	 */
-	spinlock_t cq_cached_prod_lock;
 	struct xdp_buff_xsk *free_heads[];
 };
 
diff --git a/net/xdp/xsk.c b/net/xdp/xsk.c
index b63409b1422e..ae8a92c168b8 100644
--- a/net/xdp/xsk.c
+++ b/net/xdp/xsk.c
@@ -546,17 +546,6 @@ static int xsk_wakeup(struct xdp_sock *xs, u8 flags)
 	return dev->netdev_ops->ndo_xsk_wakeup(dev, xs->queue_id, flags);
 }
 
-static int xsk_cq_reserve_locked(struct xsk_buff_pool *pool)
-{
-	int ret;
-
-	spin_lock(&pool->cq_cached_prod_lock);
-	ret = xsk_cq_cached_prod_reserve(pool->cq);
-	spin_unlock(&pool->cq_cached_prod_lock);
-
-	return ret;
-}
-
 static void xsk_cq_submit_addr_locked(struct xsk_buff_pool *pool,
 				      struct sk_buff *skb)
 {
@@ -585,11 +574,9 @@ static void xsk_cq_submit_addr_locked(struct xsk_buff_pool *pool,
 	spin_unlock_irqrestore(&pool->cq_prod_lock, flags);
 }
 
-static void xsk_cq_cancel_locked(struct xsk_buff_pool *pool, u32 n)
+static void xsk_cq_cached_prod_cancel(struct xsk_buff_pool *pool, u32 n)
 {
-	spin_lock(&pool->cq_cached_prod_lock);
 	atomic_sub(n, &pool->cq->cached_prod_atomic);
-	spin_unlock(&pool->cq_cached_prod_lock);
 }
 
 static void xsk_inc_num_desc(struct sk_buff *skb)
@@ -643,7 +630,7 @@ static void xsk_consume_skb(struct sk_buff *skb)
 	}
 
 	skb->destructor = sock_wfree;
-	xsk_cq_cancel_locked(xs->pool, num_descs);
+	xsk_cq_cached_prod_cancel(xs->pool, num_descs);
 	/* Free skb without triggering the perf drop trace */
 	consume_skb(skb);
 	xs->skb = NULL;
@@ -860,7 +847,7 @@ static struct sk_buff *xsk_build_skb(struct xdp_sock *xs,
 		xskq_cons_release(xs->tx);
 	} else {
 		/* Let application retry */
-		xsk_cq_cancel_locked(xs->pool, 1);
+		xsk_cq_cached_prod_cancel(xs->pool, 1);
 	}
 
 	return ERR_PTR(err);
@@ -898,7 +885,7 @@ static int __xsk_generic_xmit(struct sock *sk)
 		 * if there is space in it. This avoids having to implement
 		 * any buffering in the Tx path.
 		 */
-		err = xsk_cq_reserve_locked(xs->pool);
+		err = xsk_cq_cached_prod_reserve(xs->pool->cq);
 		if (err) {
 			err = -EAGAIN;
 			goto out;
diff --git a/net/xdp/xsk_buff_pool.c b/net/xdp/xsk_buff_pool.c
index 51526034c42a..9539f121b290 100644
--- a/net/xdp/xsk_buff_pool.c
+++ b/net/xdp/xsk_buff_pool.c
@@ -91,7 +91,6 @@ struct xsk_buff_pool *xp_create_and_assign_umem(struct xdp_sock *xs,
 	INIT_LIST_HEAD(&pool->xsk_tx_list);
 	spin_lock_init(&pool->xsk_tx_list_lock);
 	spin_lock_init(&pool->cq_prod_lock);
-	spin_lock_init(&pool->cq_cached_prod_lock);
 	refcount_set(&pool->users, 1);
 
 	pool->fq = xs->fq_tmp;
-- 
2.41.3