Re: [dpdk-dev] [PATCH v3] bonding: fix the segfault caused by the race condition between master thread and eal-intr-thread

[Radu Nicolau <radu.nicolau@intel.com>]

Hi,

Wouldn't be possible to treat the section of code that segfaults as a 
critical one, i.e. use the lock/unlock instead of triggering alarms?


On 7/26/2017 11:13 AM, zhangsha.zhang@huawei.com wrote:
> From: Sha Zhang <zhangsha.zhang@huawei.com>
>
> Function slave_configure calls functions bond_ethdev_lsc_event_callback and
> slave_eth_dev->dev_ops->link_update to fix updating slave link status.
> But there is a low probability that process may be crashed if the master
> thread, which create bonding-device, adds the active_slave_count of the
> bond to nozero while the rx_ring or tx_ring of it haven't been created.
>
> This patch moves the functions bond_ethdev_lsc_event_callback and
> slave_eth_dev->dev_ops->link_update to eal-intr-thread to aviod the
> competition.
>
> Fixes: 210903803f6e ("net/bonding: fix updating slave link status")
>
> Signed-off-by: Sha Zhang <zhangsha.zhang@huawei.com>
> ---
>   drivers/net/bonding/rte_eth_bond_pmd.c | 58 +++++++++++++++++++++++++++++-----
>   1 file changed, 50 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/net/bonding/rte_eth_bond_pmd.c b/drivers/net/bonding/rte_eth_bond_pmd.c
> index 383e27c..bc0ee7f 100644
> --- a/drivers/net/bonding/rte_eth_bond_pmd.c
> +++ b/drivers/net/bonding/rte_eth_bond_pmd.c
> @@ -53,6 +53,7 @@
>   
>   #define REORDER_PERIOD_MS 10
>   #define DEFAULT_POLLING_INTERVAL_10_MS (10)
> +#define BOND_LSC_DELAY_TIME_US (10 * 1000)
>   
>   #define HASH_L4_PORTS(h) ((h)->src_port ^ (h)->dst_port)
>   
> @@ -1800,14 +1801,6 @@ struct bwg_slave {
>   		}
>   	}
>   
> -	/* If lsc interrupt is set, check initial slave's link status */
> -	if (slave_eth_dev->data->dev_flags & RTE_ETH_DEV_INTR_LSC) {
> -		slave_eth_dev->dev_ops->link_update(slave_eth_dev, 0);
> -		bond_ethdev_lsc_event_callback(slave_eth_dev->data->port_id,
> -			RTE_ETH_EVENT_INTR_LSC, &bonded_eth_dev->data->port_id,
> -			NULL);
> -	}
> -
>   	return 0;
>   }
>   
> @@ -1878,6 +1871,51 @@ struct bwg_slave {
>   static void
>   bond_ethdev_promiscuous_enable(struct rte_eth_dev *eth_dev);
>   
> +static void
> +bond_ethdev_slave_lsc_delay(void *cb_arg)
> +{
> +	struct rte_eth_dev *bonded_ethdev, *slave_dev;
> +	struct bond_dev_private *internals;
> +
> +	/* Default value for polling slave found is true as we don't
> +	 *  want todisable the polling thread if we cannot get the lock.
> +	 */
> +	int i = 0;
> +
> +	if (!cb_arg)
> +		return;
> +
> +	bonded_ethdev = (struct rte_eth_dev *)cb_arg;
> +	if (!bonded_ethdev->data->dev_started)
> +		return;
> +
> +	internals = (struct bond_dev_private *)bonded_ethdev->data->dev_private;
> +	if (!rte_spinlock_trylock(&internals->lock)) {
> +		rte_eal_alarm_set(BOND_LSC_DELAY_TIME_US * 10,
> +				  bond_ethdev_slave_lsc_delay,
> +				  (void *)&rte_eth_devices[internals->port_id]);
> +		return;
> +	}
> +
> +	for (i = 0; i < internals->slave_count; i++) {
> +		slave_dev = &(rte_eth_devices[internals->slaves[i].port_id]);
> +		if (slave_dev->data->dev_conf.intr_conf.lsc != 0) {
> +			if (slave_dev->dev_ops &&
> +			    slave_dev->dev_ops->link_update)
> +				slave_dev->dev_ops->link_update(slave_dev, 0);
> +			bond_ethdev_lsc_event_callback(
> +				internals->slaves[i].port_id,
> +				RTE_ETH_EVENT_INTR_LSC,
> +				&bonded_ethdev->data->port_id, NULL);
> +		}
> +	}
> +	rte_spinlock_unlock(&internals->lock);
> +	RTE_LOG(INFO, EAL,
> +		"bond %s(%u): slave num %d, current active slave num %d\n",
> +		bonded_ethdev->data->name, bonded_ethdev->data->port_id,
> +		internals->slave_count, internals->active_slave_count);
> +}
> +
>   static int
>   bond_ethdev_start(struct rte_eth_dev *eth_dev)
>   {
> @@ -1953,6 +1991,10 @@ struct bwg_slave {
>   		if (internals->slaves[i].link_status_poll_enabled)
>   			internals->link_status_polling_enabled = 1;
>   	}
> +
> +	rte_eal_alarm_set(BOND_LSC_DELAY_TIME_US, bond_ethdev_slave_lsc_delay,
> +			  (void *)&rte_eth_devices[internals->port_id]);
> +
>   	/* start polling if needed */
>   	if (internals->link_status_polling_enabled) {
>   		rte_eal_alarm_set(