netdev - [PATCH net 5/8] Revert "iavf: Detach device during reset task"

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Message-Id: <20230717175205.3217774-6-anthony.l.nguyen@intel.com>
Date: Mon, 17 Jul 2023 10:52:02 -0700
From: Tony Nguyen <anthony.l.nguyen@...el.com>
To: davem@...emloft.net,
	kuba@...nel.org,
	pabeni@...hat.com,
	edumazet@...gle.com,
	netdev@...r.kernel.org
Cc: Marcin Szycik <marcin.szycik@...ux.intel.com>,
	anthony.l.nguyen@...el.com,
	ivecera@...hat.com,
	sassmann@...nic.de,
	Dawid Wesierski <dawidx.wesierski@...el.com>,
	Mateusz Palczewski <mateusz.palczewski@...el.com>,
	Rafal Romanowski <rafal.romanowski@...el.com>
Subject: [PATCH net 5/8] Revert "iavf: Detach device during reset task"

From: Marcin Szycik <marcin.szycik@...ux.intel.com>

This reverts commit aa626da947e9cd30c4cf727493903e1adbb2c0a0.

Detaching device during reset was not fully fixing the rtnl locking issue,
as there could be a situation where callback was already in progress before
detaching netdev.

Furthermore, detaching netdevice causes TX timeouts if traffic is running.
To reproduce:

ip netns exec ns1 iperf3 -c $PEER_IP -t 600 --logfile /dev/null &
while :; do
        for i in 200 7000 400 5000 300 3000 ; do
		ip netns exec ns1 ip link set $VF1 mtu $i
                sleep 2
        done
        sleep 10
done

Currently, callbacks such as iavf_change_mtu() wait for the reset.
If the reset fails to acquire the rtnl_lock, they schedule the netdev
update for later while continuing the reset flow. Operations like MTU
changes are performed under the rtnl_lock. Therefore, when the operation
finishes, another callback that uses rtnl_lock can start.

Signed-off-by: Dawid Wesierski <dawidx.wesierski@...el.com>
Signed-off-by: Marcin Szycik <marcin.szycik@...ux.intel.com>
Signed-off-by: Mateusz Palczewski <mateusz.palczewski@...el.com>
Tested-by: Rafal Romanowski <rafal.romanowski@...el.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@...el.com>
---
 drivers/net/ethernet/intel/iavf/iavf_main.c | 13 ++-----------
 1 file changed, 2 insertions(+), 11 deletions(-)

diff --git a/drivers/net/ethernet/intel/iavf/iavf_main.c b/drivers/net/ethernet/intel/iavf/iavf_main.c
index b89933aa5bfe..957ad6e63f6f 100644
--- a/drivers/net/ethernet/intel/iavf/iavf_main.c
+++ b/drivers/net/ethernet/intel/iavf/iavf_main.c
@@ -2977,11 +2977,6 @@ static void iavf_reset_task(struct work_struct *work)
 	int i = 0, err;
 	bool running;
 
-	/* Detach interface to avoid subsequent NDO callbacks */
-	rtnl_lock();
-	netif_device_detach(netdev);
-	rtnl_unlock();
-
 	/* When device is being removed it doesn't make sense to run the reset
 	 * task, just return in such a case.
 	 */
@@ -2989,7 +2984,7 @@ static void iavf_reset_task(struct work_struct *work)
 		if (adapter->state != __IAVF_REMOVE)
 			queue_work(adapter->wq, &adapter->reset_task);
 
-		goto reset_finish;
+		return;
 	}
 
 	while (!mutex_trylock(&adapter->client_lock))
@@ -3192,7 +3187,7 @@ static void iavf_reset_task(struct work_struct *work)
 	mutex_unlock(&adapter->client_lock);
 	mutex_unlock(&adapter->crit_lock);
 
-	goto reset_finish;
+	return;
 reset_err:
 	if (running) {
 		set_bit(__IAVF_VSI_DOWN, adapter->vsi.state);
@@ -3213,10 +3208,6 @@ static void iavf_reset_task(struct work_struct *work)
 	}
 
 	dev_err(&adapter->pdev->dev, "failed to allocate resources during reinit\n");
-reset_finish:
-	rtnl_lock();
-	netif_device_attach(netdev);
-	rtnl_unlock();
 }
 
 /**
-- 
2.38.1