linux-kernel - [PATCH 5.15 549/917] nfp: fix potential deadlock when canceling dim work

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Message-Id: <20211115165447.402050472@linuxfoundation.org>
Date:   Mon, 15 Nov 2021 18:00:44 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Yinjun Zhang <yinjun.zhang@...igine.com>,
        Louis Peens <louis.peens@...igine.com>,
        Simon Horman <simon.horman@...igine.com>,
        "David S. Miller" <davem@...emloft.net>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.15 549/917] nfp: fix potential deadlock when canceling dim work

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

[ Upstream commit 17e712c6a1bade9dac02a7bf2b464746faa7e9a0 ]

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>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 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 f8b880c8e5148..850bfdf83d0a4 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;
 }
-- 
2.33.0