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SubjectRE: [PATCH net] iavf: Detach device during reset task
Date
> -----Original Message-----
> From: ivecera <ivecera@redhat.com>
> Sent: Thursday, August 18, 2022 6:56 PM
> To: netdev@vger.kernel.org
> Cc: Keller, Jacob E <jacob.e.keller@intel.com>; Piotrowski, Patryk
> <patryk.piotrowski@intel.com>; Vitaly Grinberg <vgrinber@redhat.com>;
> Brandeburg, Jesse <jesse.brandeburg@intel.com>; Nguyen, Anthony L
> <anthony.l.nguyen@intel.com>; David S. Miller <davem@davemloft.net>; Eric
> Dumazet <edumazet@google.com>; Jakub Kicinski <kuba@kernel.org>; Paolo
> Abeni <pabeni@redhat.com>; Jeff Kirsher <jeffrey.t.kirsher@intel.com>;
> moderated list:INTEL ETHERNET DRIVERS <intel-wired-lan@lists.osuosl.org>;
> open list <linux-kernel@vger.kernel.org>
> Subject: [PATCH net] iavf: Detach device during reset task
>
> iavf_reset_task() takes crit_lock at the beginning and holds it during whole call.
> The function subsequently calls
> iavf_init_interrupt_scheme() that grabs RTNL. Problem occurs when userspace
> initiates during the reset task any ndo callback that runs under RTNL like
> iavf_open() because some of that functions tries to take crit_lock. This leads to
> classic A-B B-A deadlock scenario.
>
> To resolve this situation the device should be detached in
> iavf_reset_task() prior taking crit_lock to avoid subsequent ndos running under
> RTNL and reattach the device at the end.
>
> Fixes: 62fe2a865e6d ("i40evf: add missing rtnl_lock() around
> i40evf_set_interrupt_capability")
> Cc: Jacob Keller <jacob.e.keller@intel.com>
> Cc: Patryk Piotrowski <patryk.piotrowski@intel.com>
> Tested-by: Vitaly Grinberg <vgrinber@redhat.com>
> Signed-off-by: Ivan Vecera <ivecera@redhat.com>
> ---
> drivers/net/ethernet/intel/iavf/iavf_main.c | 22 +++++++++++++++------
> 1 file changed, 16 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/net/ethernet/intel/iavf/iavf_main.c
> b/drivers/net/ethernet/intel/iavf/iavf_main.c
> index f39440ad5c50..ee8f911b57ea 100644
> --- a/drivers/net/ethernet/intel/iavf/iavf_main.c
> +++ b/drivers/net/ethernet/intel/iavf/iavf_main.c
> @@ -2877,6 +2877,13 @@ static void iavf_reset_task(struct work_struct
> *work)
> int i = 0, err;
> bool running;
>
> + /*
> + * Detach interface to avoid subsequent NDO callbacks
> + */

nit:
The comment should start this way: /* Detach ...

> + 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.
> */
> @@ -2884,7 +2891,7 @@ static void iavf_reset_task(struct work_struct *work)
> if (adapter->state != __IAVF_REMOVE)
> queue_work(iavf_wq, &adapter->reset_task);
>
> - return;
> + goto reset_finish;

Correct me if I'm wrong.
In case when you fail to grab a crit_lock you'd jump to the reset_finish label and unlock the locks you didn't lock.

> }
>
> while (!mutex_trylock(&adapter->client_lock))
> @@ -2954,7 +2961,6 @@ static void iavf_reset_task(struct work_struct *work)
>
> if (running) {
> netif_carrier_off(netdev);
> - netif_tx_stop_all_queues(netdev);
> adapter->link_up = false;
> iavf_napi_disable_all(adapter);
> }
> @@ -3081,10 +3087,8 @@ static void iavf_reset_task(struct work_struct
> *work)
>
> adapter->flags &= ~IAVF_FLAG_REINIT_ITR_NEEDED;
>
> - 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); @@ -3092,9
> +3096,15 @@ static void iavf_reset_task(struct work_struct *work)
> }
> iavf_disable_vf(adapter);
>
> + dev_err(&adapter->pdev->dev, "failed to allocate resources during
> +reinit\n");
> +
> +reset_finish:
> mutex_unlock(&adapter->client_lock);
> mutex_unlock(&adapter->crit_lock);
> - dev_err(&adapter->pdev->dev, "failed to allocate resources during
> reinit\n");
> +
> + rtnl_lock();
> + netif_device_attach(netdev);
> + rtnl_unlock();
> }
>
> /**
> --
> 2.35.1

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