netdev - [PATCH net 2/2] nfp: fix potential deadlock when canceling dim work

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Date:   Fri, 29 Oct 2021 13:29:03 +0200
From:   Simon Horman <simon.horman@...igine.com>
To:     David Miller <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>
Cc:     netdev@...r.kernel.org, oss-drivers@...igine.com,
        Yinjun Zhang <yinjun.zhang@...igine.com>,
        Louis Peens <louis.peens@...igine.com>,
        Simon Horman <simon.horman@...igine.com>
Subject: [PATCH net 2/2] nfp: fix potential deadlock when canceling dim work

From: Yinjun Zhang <yinjun.zhang@...igine.com>

When port is linked down, the process which has acquired rtnl_lock
will wait for the in-progress dim work to finish, and the work also
acquires rtnl_lock, which may cause deadlock.

Currently IRQ_MOD registers can be configured by `ethtool -C` and
dim work, and which will take effect depends on the execution order,
rtnl_lock is useless here, so remove them.

Fixes: 9d32e4e7e9e1 ("nfp: add support for coalesce adaptive feature")
Signed-off-by: Yinjun Zhang <yinjun.zhang@...igine.com>
Signed-off-by: Louis Peens <louis.peens@...igine.com>
Signed-off-by: Simon Horman <simon.horman@...igine.com>
---
 drivers/net/ethernet/netronome/nfp/nfp_net_common.c | 4 ----
 1 file changed, 4 deletions(-)

diff --git a/drivers/net/ethernet/netronome/nfp/nfp_net_common.c b/drivers/net/ethernet/netronome/nfp/nfp_net_common.c
index f8b880c8e514..850bfdf83d0a 100644
--- a/drivers/net/ethernet/netronome/nfp/nfp_net_common.c
+++ b/drivers/net/ethernet/netronome/nfp/nfp_net_common.c
@@ -3016,10 +3016,8 @@ static void nfp_net_rx_dim_work(struct work_struct *work)
 
 	/* copy RX interrupt coalesce parameters */
 	value = (moder.pkts << 16) | (factor * moder.usec);
-	rtnl_lock();
 	nn_writel(nn, NFP_NET_CFG_RXR_IRQ_MOD(r_vec->rx_ring->idx), value);
 	(void)nfp_net_reconfig(nn, NFP_NET_CFG_UPDATE_IRQMOD);
-	rtnl_unlock();
 
 	dim->state = DIM_START_MEASURE;
 }
@@ -3047,10 +3045,8 @@ static void nfp_net_tx_dim_work(struct work_struct *work)
 
 	/* copy TX interrupt coalesce parameters */
 	value = (moder.pkts << 16) | (factor * moder.usec);
-	rtnl_lock();
 	nn_writel(nn, NFP_NET_CFG_TXR_IRQ_MOD(r_vec->tx_ring->idx), value);
 	(void)nfp_net_reconfig(nn, NFP_NET_CFG_UPDATE_IRQMOD);
-	rtnl_unlock();
 
 	dim->state = DIM_START_MEASURE;
 }
-- 
2.20.1