[PATCH net 0/2] nfp: fix bugs caused by adaptive coalesce

Hi,

this series contains fixes for two bugs introduced when
when adaptive coalesce support was added to the NFP driver in
v5.15 by 9d32e4e7e9e1 ("nfp: add support for coalesce adaptive feature")

Yinjun Zhang (2):
  nfp: fix NULL pointer access when scheduling dim work
  nfp: fix potential deadlock when canceling dim work

 drivers/net/ethernet/netronome/nfp/nfp_net_common.c | 8 ++------
 1 file changed, 2 insertions(+), 6 deletions(-)

-- 
2.20.1

From: Yinjun Zhang <redacted>

Each rx/tx ring has a related dim work, when rx/tx ring number is
decreased by `ethtool -L`, the corresponding rx_ring or tx_ring is
assigned NULL, while its related work is not destroyed. When scheduled,
the work will access NULL pointer.

Fixes: 9d32e4e7e9e1 ("nfp: add support for coalesce adaptive feature")
Signed-off-by: Yinjun Zhang <redacted>
Signed-off-by: Louis Peens <redacted>
Signed-off-by: Simon Horman <redacted>
---
 drivers/net/ethernet/netronome/nfp/nfp_net_common.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/netronome/nfp/nfp_net_common.c b/drivers/net/ethernet/netronome/nfp/nfp_net_common.c
index 5bfa22accf2c..f8b880c8e514 100644
--- a/drivers/net/ethernet/netronome/nfp/nfp_net_common.c
+++ b/drivers/net/ethernet/netronome/nfp/nfp_net_common.c

@@ -2067,7 +2067,7 @@ static int nfp_net_poll(struct napi_struct *napi, int budget)
 		if (napi_complete_done(napi, pkts_polled))
 			nfp_net_irq_unmask(r_vec->nfp_net, r_vec->irq_entry);
 
-	if (r_vec->nfp_net->rx_coalesce_adapt_on) {
+	if (r_vec->nfp_net->rx_coalesce_adapt_on && r_vec->rx_ring) {
 		struct dim_sample dim_sample = {};
 		unsigned int start;
 		u64 pkts, bytes;

@@ -2082,7 +2082,7 @@ static int nfp_net_poll(struct napi_struct *napi, int budget)
 		net_dim(&r_vec->rx_dim, dim_sample);
 	}
 
-	if (r_vec->nfp_net->tx_coalesce_adapt_on) {
+	if (r_vec->nfp_net->tx_coalesce_adapt_on && r_vec->tx_ring) {
 		struct dim_sample dim_sample = {};
 		unsigned int start;
 		u64 pkts, bytes;

-- 
2.20.1

From: Yinjun Zhang <redacted>

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 <redacted>
Signed-off-by: Louis Peens <redacted>
Signed-off-by: Simon Horman <redacted>
---
 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

Hello:

This series was applied to netdev/net.git (master)
by David S. Miller [off-list ref]:

On Fri, 29 Oct 2021 13:29:01 +0200 you wrote:

Hi,

this series contains fixes for two bugs introduced when
when adaptive coalesce support was added to the NFP driver in
v5.15 by 9d32e4e7e9e1 ("nfp: add support for coalesce adaptive feature")

Yinjun Zhang (2):
  nfp: fix NULL pointer access when scheduling dim work
  nfp: fix potential deadlock when canceling dim work

[...]

Here is the summary with links:
  - [net,1/2] nfp: fix NULL pointer access when scheduling dim work
    https://git.kernel.org/netdev/net/c/f8d384a640dd
  - [net,2/2] nfp: fix potential deadlock when canceling dim work
    https://git.kernel.org/netdev/net/c/17e712c6a1ba

You are awesome, thank you!
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