linux-kernel - [PATCH net-next v2 1/4] net: mana: Fix potential deadlocks in mana napi ops

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Message-Id: <1749813627-8377-2-git-send-email-ernis@linux.microsoft.com>
Date: Fri, 13 Jun 2025 04:20:24 -0700
From: Erni Sri Satya Vennela <ernis@...ux.microsoft.com>
To: kys@...rosoft.com,
	haiyangz@...rosoft.com,
	wei.liu@...nel.org,
	decui@...rosoft.com,
	andrew+netdev@...n.ch,
	davem@...emloft.net,
	edumazet@...gle.com,
	kuba@...nel.org,
	pabeni@...hat.com,
	longli@...rosoft.com,
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	horms@...nel.org,
	shirazsaleem@...rosoft.com,
	leon@...nel.org,
	ernis@...ux.microsoft.com,
	shradhagupta@...ux.microsoft.com,
	schakrabarti@...ux.microsoft.com,
	gerhard@...leder-embedded.com,
	rosenp@...il.com,
	sdf@...ichev.me,
	linux-hyperv@...r.kernel.org,
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	linux-rdma@...r.kernel.org
Subject: [PATCH net-next v2 1/4] net: mana: Fix potential deadlocks in mana napi ops

When net_shaper_ops are enabled for MANA, netdev_ops_lock
becomes active.

MANA VF setup/teardown by netvsc follows this call chain:

netvsc_vf_setup()
        dev_change_flags()
		...
         __dev_open() OR __dev_close()

dev_change_flags() holds the netdev mutex via netdev_lock_ops.

Meanwhile, mana_create_txq() and mana_create_rxq() in mana_open()
path call NAPI APIs (netif_napi_add_tx(), netif_napi_add_weight(),
napi_enable()), which also try to acquire the same lock, risking
deadlock.

Similarly in the teardown path (mana_close()), netif_napi_disable()
and netif_napi_del(), contend for the same lock.

Switch to the _locked variants of these APIs to avoid deadlocks
when the netdev_ops_lock is held.

Fixes: d4c22ec680c8 ("net: hold netdev instance lock during ndo_open/ndo_stop")
Signed-off-by: Erni Sri Satya Vennela <ernis@...ux.microsoft.com>
Reviewed-by: Haiyang Zhang <haiyangz@...rosoft.com>
Reviewed-by: Shradha Gupta <shradhagupta@...ux.microsoft.com>
Reviewed-by: Saurabh Singh Sengar <ssengar@...ux.microsoft.com>
---
Changes in v2:
* Use netdev_lock_ops_to_full() instead of if...else statements for napi
  APIs.
* Edit commit message.
---
 drivers/net/ethernet/microsoft/mana/mana_en.c | 30 +++++++++++++------
 1 file changed, 21 insertions(+), 9 deletions(-)

diff --git a/drivers/net/ethernet/microsoft/mana/mana_en.c b/drivers/net/ethernet/microsoft/mana/mana_en.c
index e68b8190bb7a..ca5e9c3d374b 100644
--- a/drivers/net/ethernet/microsoft/mana/mana_en.c
+++ b/drivers/net/ethernet/microsoft/mana/mana_en.c
@@ -1912,8 +1912,11 @@ static void mana_destroy_txq(struct mana_port_context *apc)
 		napi = &apc->tx_qp[i].tx_cq.napi;
 		if (apc->tx_qp[i].txq.napi_initialized) {
 			napi_synchronize(napi);
-			napi_disable(napi);
-			netif_napi_del(napi);
+			netdev_lock_ops_to_full(napi->dev);
+			napi_disable_locked(napi);
+			netif_napi_del_locked(napi);
+			netdev_unlock_full_to_ops(napi->dev);
 			apc->tx_qp[i].txq.napi_initialized = false;
 		}
 		mana_destroy_wq_obj(apc, GDMA_SQ, apc->tx_qp[i].tx_object);
@@ -2065,8 +2068,11 @@ static int mana_create_txq(struct mana_port_context *apc,
 
 		mana_create_txq_debugfs(apc, i);
 
-		netif_napi_add_tx(net, &cq->napi, mana_poll);
-		napi_enable(&cq->napi);
+		set_bit(NAPI_STATE_NO_BUSY_POLL, &cq->napi.state);
+		netdev_lock_ops_to_full(net);
+		netif_napi_add_locked(net, &cq->napi, mana_poll);
+		napi_enable_locked(&cq->napi);
+		netdev_unlock_full_to_ops(net);
 		txq->napi_initialized = true;
 
 		mana_gd_ring_cq(cq->gdma_cq, SET_ARM_BIT);
@@ -2102,9 +2108,11 @@ static void mana_destroy_rxq(struct mana_port_context *apc,
 	if (napi_initialized) {
 		napi_synchronize(napi);
 
-		napi_disable(napi);
-
-		netif_napi_del(napi);
+		netdev_lock_ops_to_full(napi->dev);
+		napi_disable_locked(napi);
+		netif_napi_del_locked(napi);
+		netdev_unlock_full_to_ops(napi->dev);
 	}
 	xdp_rxq_info_unreg(&rxq->xdp_rxq);
 
@@ -2355,14 +2363,18 @@ static struct mana_rxq *mana_create_rxq(struct mana_port_context *apc,
 
 	gc->cq_table[cq->gdma_id] = cq->gdma_cq;
 
-	netif_napi_add_weight(ndev, &cq->napi, mana_poll, 1);
+	netdev_lock_ops_to_full(ndev);
+	netif_napi_add_weight_locked(ndev, &cq->napi, mana_poll, 1);
+	netdev_unlock_full_to_ops(ndev);
 
 	WARN_ON(xdp_rxq_info_reg(&rxq->xdp_rxq, ndev, rxq_idx,
 				 cq->napi.napi_id));
 	WARN_ON(xdp_rxq_info_reg_mem_model(&rxq->xdp_rxq, MEM_TYPE_PAGE_POOL,
 					   rxq->page_pool));
 
-	napi_enable(&cq->napi);
+	netdev_lock_ops_to_full(ndev);
+	napi_enable_locked(&cq->napi);
+	netdev_unlock_full_to_ops(ndev);
 
 	mana_gd_ring_cq(cq->gdma_cq, SET_ARM_BIT);
 out:
-- 
2.34.1