RE: [PATCH] net/iavf: fix iavf query stats in intr thread

["Zhang, Qi Z" <qi.z.zhang@intel.com>]

> -----Original Message-----
> From: Deng, KaiwenX <kaiwenx.deng@intel.com>
> Sent: Wednesday, February 22, 2023 12:40 PM
> To: dev@dpdk.org
> Cc: stable@dpdk.org; Yang, Qiming <qiming.yang@intel.com>; Zhou, YidingX
> <yidingx.zhou@intel.com>; Deng, KaiwenX <kaiwenx.deng@intel.com>; Wu,
> Jingjing <jingjing.wu@intel.com>; Xing, Beilei <beilei.xing@intel.com>; Zhang,
> Qi Z <qi.z.zhang@intel.com>
> Subject: [PATCH] net/iavf: fix iavf query stats in intr thread
> 
> When iavf send query-stats command in eal-intr-thread through virtual
> channel, there will be no response received from iavf_dev_virtchnl_handler
> for this command during block and wait.
> Because iavf_dev_virtchnl_handler is also registered in eal-intr-thread.
> 
> When vf device is bonded as BONDING_MODE_TLB mode, the slave update
> callback will registered in alarm and called by eal-intr-thread, it would also
> raise the above issue.
> 
> This commit add local stats return to iavf_dev_stats_get immediately when it
> is called by eal-intr-thread. And update local stats in iavf-virtchnl-thread.
> 
> Fixes: cb5c1b91f76f ("net/iavf: add thread for event callbacks")
> Fixes: 22b123a36d07 ("net/avf: initialize PMD")
> Cc: stable@dpdk.org
> 
> Signed-off-by: Kaiwen Deng <kaiwenx.deng@intel.com>
> ---
>  drivers/net/iavf/iavf.h        |   9 ++-
>  drivers/net/iavf/iavf_ethdev.c |  24 ++++++--  drivers/net/iavf/iavf_vchnl.c  |
> 107 ++++++++++++++++++++++++---------
>  3 files changed, 104 insertions(+), 36 deletions(-)
> 
> diff --git a/drivers/net/iavf/iavf.h b/drivers/net/iavf/iavf.h index
> 1edebab8dc..3a249b90a3 100644
> --- a/drivers/net/iavf/iavf.h
> +++ b/drivers/net/iavf/iavf.h
> @@ -128,6 +128,7 @@ struct iavf_vsi {
>  	uint16_t base_vector;
>  	uint16_t msix_intr;      /* The MSIX interrupt binds to VSI */
>  	struct iavf_eth_xstats eth_stats_offset;
> +	struct virtchnl_eth_stats eth_stats;
>  };
> 
>  struct rte_flow;
> @@ -325,6 +326,8 @@ struct iavf_adapter {
>  	struct iavf_devargs devargs;
>  };
> 
> +typedef void (*virtchnl_callback)(struct rte_eth_dev *dev, void *args);
> +
>  /* IAVF_DEV_PRIVATE_TO */
>  #define IAVF_DEV_PRIVATE_TO_ADAPTER(adapter) \
>  	((struct iavf_adapter *)adapter)
> @@ -424,8 +427,10 @@ _atomic_set_async_response_cmd(struct iavf_info
> *vf, enum virtchnl_ops ops)  }  int iavf_check_api_version(struct iavf_adapter
> *adapter);  int iavf_get_vf_resource(struct iavf_adapter *adapter); -void
> iavf_dev_event_handler_fini(void);
> -int iavf_dev_event_handler_init(void);
> +void iavf_dev_virtchnl_handler_fini(void);
> +void iavf_dev_virtchnl_callback_post(struct rte_eth_dev *dev,
> +			 virtchnl_callback cb, void *args);
> +int iavf_dev_virtchnl_handler_init(void);
>  void iavf_handle_virtchnl_msg(struct rte_eth_dev *dev);  int
> iavf_enable_vlan_strip(struct iavf_adapter *adapter);  int
> iavf_disable_vlan_strip(struct iavf_adapter *adapter); diff --git
> a/drivers/net/iavf/iavf_ethdev.c b/drivers/net/iavf/iavf_ethdev.c index
> 3196210f2c..fcbab5b26a 100644
> --- a/drivers/net/iavf/iavf_ethdev.c
> +++ b/drivers/net/iavf/iavf_ethdev.c
> @@ -1729,6 +1729,17 @@ iavf_update_stats(struct iavf_vsi *vsi, struct
> virtchnl_eth_stats *nes)
>  	iavf_stat_update_32(&oes->tx_discards, &nes->tx_discards);  }
> 
> +static void iavf_dev_stats_get_callback(struct rte_eth_dev *dev, void
> +*args) {
> +	struct virtchnl_eth_stats *eth_stats = (struct virtchnl_eth_stats *)args;
> +	struct virtchnl_eth_stats *pstats = NULL;
> +	struct iavf_adapter *adapter =
> +		IAVF_DEV_PRIVATE_TO_ADAPTER(dev->data->dev_private);
> +	int ret = iavf_query_stats(adapter, &pstats);
> +	if (ret == 0)
> +		rte_memcpy(eth_stats, pstats, sizeof(struct
> virtchnl_eth_stats)); }
> +
>  static int
>  iavf_dev_stats_get(struct rte_eth_dev *dev, struct rte_eth_stats *stats)
> { @@ -1738,8 +1749,13 @@ iavf_dev_stats_get(struct rte_eth_dev *dev,
> struct rte_eth_stats *stats)
>  	struct iavf_vsi *vsi = &vf->vsi;
>  	struct virtchnl_eth_stats *pstats = NULL;
>  	int ret;
> -
> -	ret = iavf_query_stats(adapter, &pstats);
> +	if (rte_thread_is_intr()) {
> +		pstats = &vsi->eth_stats;
> +		iavf_dev_virtchnl_callback_post(dev,
> iavf_dev_stats_get_callback, (void *)pstats);
> +		ret = 0;


I assume this is going to return a copy of outdated stats, then the stats will be updated it in future and this happens in another thread, is it correct?
If true, then will be 2 issues.
1. How the caller know when the updated data will be ready?
2. even caller will consume the outdated stats directly, is that will be a race condition if the virtchnl thread update the stats at the same time?

> +	} else {
> +		ret = iavf_query_stats(adapter, &pstats);
> +	}
>  	if (ret == 0) {
>  		uint8_t crc_stats_len = (dev->data-
> >dev_conf.rxmode.offloads &
>  					 RTE_ETH_RX_OFFLOAD_KEEP_CRC) ?
> 0 :