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Message-Id: <1542796841.15177.14.camel@abdul>
Date: Wed, 21 Nov 2018 16:10:41 +0530
From: Abdul Haleem <abdhalee@...ux.vnet.ibm.com>
To: Juliet Kim <julietk@...ux.vnet.ibm.com>
Cc: netdev@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
mwb@...ux.vnet.ibm.com, tlfalcon@...ux.vnet.ibm.com,
tyreld@...ux.vnet.ibm.com
Subject: Re: [PATCH net] net/ibmnvic: Fix deadlock problem in reset
On Mon, 2018-11-19 at 15:59 -0600, Juliet Kim wrote:
> This patch changes to use rtnl_lock only during a reset to avoid
> deadlock that could occur when a thread operating close is holding
> rtnl_lock and waiting for reset_lock acquired by another thread,
> which is waiting for rtnl_lock in order to set the number of tx/rx
> queues during a reset.
>
> Also, we now setting the number of tx/rx queues during a soft reset
> for failover or LPM events.
>
> Signed-off-by: Juliet Kim <julietk@...ux.vnet.ibm.com>
> ---
> drivers/net/ethernet/ibm/ibmvnic.c | 59 +++++++++++++-----------------------
> drivers/net/ethernet/ibm/ibmvnic.h | 2 +
> 2 files changed, 22 insertions(+), 39 deletions(-)
>
> diff --git a/drivers/net/ethernet/ibm/ibmvnic.c b/drivers/net/ethernet/ibm/ibmvnic.c
> index 7893bef..4a5de59 100644
> --- a/drivers/net/ethernet/ibm/ibmvnic.c
> +++ b/drivers/net/ethernet/ibm/ibmvnic.c
> @@ -1103,20 +1103,15 @@ static int ibmvnic_open(struct net_device *netdev)
> return 0;
> }
>
> - mutex_lock(&adapter->reset_lock);
> -
> if (adapter->state != VNIC_CLOSED) {
> rc = ibmvnic_login(netdev);
> - if (rc) {
> - mutex_unlock(&adapter->reset_lock);
> + if (rc)
> return rc;
> - }
>
> rc = init_resources(adapter);
> if (rc) {
> netdev_err(netdev, "failed to initialize resources\n");
> release_resources(adapter);
> - mutex_unlock(&adapter->reset_lock);
> return rc;
> }
> }
> @@ -1124,8 +1119,6 @@ static int ibmvnic_open(struct net_device *netdev)
> rc = __ibmvnic_open(netdev);
> netif_carrier_on(netdev);
>
> - mutex_unlock(&adapter->reset_lock);
> -
> return rc;
> }
>
> @@ -1269,10 +1262,8 @@ static int ibmvnic_close(struct net_device *netdev)
> return 0;
> }
>
> - mutex_lock(&adapter->reset_lock);
> rc = __ibmvnic_close(netdev);
> ibmvnic_cleanup(netdev);
> - mutex_unlock(&adapter->reset_lock);
>
> return rc;
> }
> @@ -1820,20 +1811,15 @@ static int do_reset(struct ibmvnic_adapter *adapter,
> return rc;
> } else if (adapter->req_rx_queues != old_num_rx_queues ||
> adapter->req_tx_queues != old_num_tx_queues) {
> - adapter->map_id = 1;
> release_rx_pools(adapter);
> release_tx_pools(adapter);
> - rc = init_rx_pools(netdev);
> - if (rc)
> - return rc;
> - rc = init_tx_pools(netdev);
> - if (rc)
> - return rc;
> -
> release_napi(adapter);
> - rc = init_napi(adapter);
> + release_vpd_data(adapter);
> +
> + rc = init_resources(adapter);
> if (rc)
> return rc;
> +
> } else {
> rc = reset_tx_pools(adapter);
> if (rc)
> @@ -1917,17 +1903,8 @@ static int do_hard_reset(struct ibmvnic_adapter *adapter,
> adapter->state = VNIC_PROBED;
> return 0;
> }
> - /* netif_set_real_num_xx_queues needs to take rtnl lock here
> - * unless wait_for_reset is set, in which case the rtnl lock
> - * has already been taken before initializing the reset
> - */
> - if (!adapter->wait_for_reset) {
> - rtnl_lock();
> - rc = init_resources(adapter);
> - rtnl_unlock();
> - } else {
> - rc = init_resources(adapter);
> - }
> +
> + rc = init_resources(adapter);
> if (rc)
> return rc;
>
> @@ -1986,13 +1963,21 @@ static void __ibmvnic_reset(struct work_struct *work)
> struct ibmvnic_rwi *rwi;
> struct ibmvnic_adapter *adapter;
> struct net_device *netdev;
> + bool we_lock_rtnl = false;
> u32 reset_state;
> int rc = 0;
>
> adapter = container_of(work, struct ibmvnic_adapter, ibmvnic_reset);
> netdev = adapter->netdev;
>
> - mutex_lock(&adapter->reset_lock);
> + /* netif_set_real_num_xx_queues needs to take rtnl lock here
> + * unless wait_for_reset is set, in which case the rtnl lock
> + * has already been taken before initializing the reset
> + */
> + if (!adapter->wait_for_reset) {
> + rtnl_lock();
> + we_lock_rtnl = true;
> + }
> reset_state = adapter->state;
>
> rwi = get_next_rwi(adapter);
> @@ -2020,12 +2005,11 @@ static void __ibmvnic_reset(struct work_struct *work)
> if (rc) {
> netdev_dbg(adapter->netdev, "Reset failed\n");
> free_all_rwi(adapter);
> - mutex_unlock(&adapter->reset_lock);
> - return;
> }
>
> adapter->resetting = false;
> - mutex_unlock(&adapter->reset_lock);
> + if (we_lock_rtnl)
> + rtnl_unlock();
> }
>
> static int ibmvnic_reset(struct ibmvnic_adapter *adapter,
> @@ -4768,7 +4752,6 @@ static int ibmvnic_probe(struct vio_dev *dev, const struct vio_device_id *id)
>
> INIT_WORK(&adapter->ibmvnic_reset, __ibmvnic_reset);
> INIT_LIST_HEAD(&adapter->rwi_list);
> - mutex_init(&adapter->reset_lock);
> mutex_init(&adapter->rwi_lock);
> adapter->resetting = false;
>
> @@ -4840,8 +4823,8 @@ static int ibmvnic_remove(struct vio_dev *dev)
> struct ibmvnic_adapter *adapter = netdev_priv(netdev);
>
> adapter->state = VNIC_REMOVING;
> - unregister_netdev(netdev);
> - mutex_lock(&adapter->reset_lock);
> + rtnl_lock();
> + unregister_netdevice(netdev);
>
> release_resources(adapter);
> release_sub_crqs(adapter, 1);
> @@ -4852,7 +4835,7 @@ static int ibmvnic_remove(struct vio_dev *dev)
>
> adapter->state = VNIC_REMOVED;
>
> - mutex_unlock(&adapter->reset_lock);
> + rtnl_unlock();
> device_remove_file(&dev->dev, &dev_attr_failover);
> free_netdev(netdev);
> dev_set_drvdata(&dev->dev, NULL);
> diff --git a/drivers/net/ethernet/ibm/ibmvnic.h b/drivers/net/ethernet/ibm/ibmvnic.h
> index 18103b8..99c4f8d 100644
> --- a/drivers/net/ethernet/ibm/ibmvnic.h
> +++ b/drivers/net/ethernet/ibm/ibmvnic.h
> @@ -1075,7 +1075,7 @@ struct ibmvnic_adapter {
> struct tasklet_struct tasklet;
> enum vnic_state state;
> enum ibmvnic_reset_reason reset_reason;
> - struct mutex reset_lock, rwi_lock;
> + struct mutex rwi_lock;
> struct list_head rwi_list;
> struct work_struct ibmvnic_reset;
> bool resetting;
>
Thanks for the fix, Please add Reported-and-tested-by: Abdul Haleem <abdhalee@...ux.vnet.ibm.com>
--
Regard's
Abdul Haleem
IBM Linux Technology Centre
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