RE: [PATCH 1/5] ethdev: fix race-condition of proactive error handling mode

[Konstantin Ananyev <konstantin.ananyev@huawei.com>]

> In the proactive error handling mode, the PMD will set the data path
> pointers to dummy functions and then try recovery, in this period the
> application may still invoking data path API. This will introduce a
> race-condition with data path which may lead to crash [1].
> 
> Although the PMD added delay after setting data path pointers to cover
> the above race-condition, it reduces the probability, but it doesn't
> solve the problem.
> 
> To solve the race-condition problem fundamentally, the following
> requirements are added:
> 1. The PMD should set the data path pointers to dummy functions after
>    report RTE_ETH_EVENT_ERR_RECOVERING event.
> 2. The application should stop data path API invocation when process
>    the RTE_ETH_EVENT_ERR_RECOVERING event.
> 3. The PMD should set the data path pointers to valid functions before
>    report RTE_ETH_EVENT_RECOVERY_SUCCESS event.
> 4. The application should enable data path API invocation when process
>    the RTE_ETH_EVENT_RECOVERY_SUCCESS event.
> 
> Also, this patch introduce a driver internal function
> rte_eth_fp_ops_setup which used as an help function for PMD.
> 
> [1] http://patchwork.dpdk.org/project/dpdk/patch/20230220060839.1267349-2-ashok.k.kaladi@intel.com/
> 
> Fixes: eb0d471a8941 ("ethdev: add proactive error handling mode")
> Cc: stable@dpdk.org
> 
> Signed-off-by: Chengwen Feng <fengchengwen@huawei.com>
> ---
>  doc/guides/prog_guide/poll_mode_drv.rst | 20 +++++++---------
>  lib/ethdev/ethdev_driver.c              |  8 +++++++
>  lib/ethdev/ethdev_driver.h              | 10 ++++++++
>  lib/ethdev/rte_ethdev.h                 | 32 +++++++++++++++----------
>  lib/ethdev/version.map                  |  1 +
>  5 files changed, 46 insertions(+), 25 deletions(-)
> 
> diff --git a/doc/guides/prog_guide/poll_mode_drv.rst b/doc/guides/prog_guide/poll_mode_drv.rst
> index c145a9066c..e380ff135a 100644
> --- a/doc/guides/prog_guide/poll_mode_drv.rst
> +++ b/doc/guides/prog_guide/poll_mode_drv.rst
> @@ -638,14 +638,9 @@ different from the application invokes recovery in PASSIVE mode,
>  the PMD automatically recovers from error in PROACTIVE mode,
>  and only a small amount of work is required for the application.
> 
> -During error detection and automatic recovery,
> -the PMD sets the data path pointers to dummy functions
> -(which will prevent the crash),
> -and also make sure the control path operations fail with a return code ``-EBUSY``.
> -
> -Because the PMD recovers automatically,
> -the application can only sense that the data flow is disconnected for a while
> -and the control API returns an error in this period.
> +During error detection and automatic recovery, the PMD sets the data path
> +pointers to dummy functions and also make sure the control path operations
> +failed with a return code ``-EBUSY``.
> 
>  In order to sense the error happening/recovering,
>  as well as to restore some additional configuration,
> @@ -653,9 +648,9 @@ three events are available:
> 
>  ``RTE_ETH_EVENT_ERR_RECOVERING``
>     Notify the application that an error is detected
> -   and the recovery is being started.
> +   and the recovery is about to start.
>     Upon receiving the event, the application should not invoke
> -   any control path function until receiving
> +   any control and data path API until receiving
>     ``RTE_ETH_EVENT_RECOVERY_SUCCESS`` or ``RTE_ETH_EVENT_RECOVERY_FAILED`` event.
> 
>  .. note::
> @@ -666,8 +661,9 @@ three events are available:
> 
>  ``RTE_ETH_EVENT_RECOVERY_SUCCESS``
>     Notify the application that the recovery from error is successful,
> -   the PMD already re-configures the port,
> -   and the effect is the same as a restart operation.
> +   the PMD already re-configures the port.
> +   The application should restore some additional configuration, and then
> +   enable data path API invocation.
> 
>  ``RTE_ETH_EVENT_RECOVERY_FAILED``
>     Notify the application that the recovery from error failed,
> diff --git a/lib/ethdev/ethdev_driver.c b/lib/ethdev/ethdev_driver.c
> index 0be1e8ca04..f994653fe9 100644
> --- a/lib/ethdev/ethdev_driver.c
> +++ b/lib/ethdev/ethdev_driver.c
> @@ -515,6 +515,14 @@ rte_eth_dma_zone_free(const struct rte_eth_dev *dev, const char *ring_name,
>  	return rc;
>  }
> 
> +void
> +rte_eth_fp_ops_setup(struct rte_eth_dev *dev)
> +{
> +	if (dev == NULL)
> +		return;
> +	eth_dev_fp_ops_setup(rte_eth_fp_ops + dev->data->port_id, dev);
> +}
> +
>  const struct rte_memzone *
>  rte_eth_dma_zone_reserve(const struct rte_eth_dev *dev, const char *ring_name,
>  			 uint16_t queue_id, size_t size, unsigned int align,
> diff --git a/lib/ethdev/ethdev_driver.h b/lib/ethdev/ethdev_driver.h
> index 2c9d615fb5..0d964d1f67 100644
> --- a/lib/ethdev/ethdev_driver.h
> +++ b/lib/ethdev/ethdev_driver.h
> @@ -1621,6 +1621,16 @@ int
>  rte_eth_dma_zone_free(const struct rte_eth_dev *eth_dev, const char *name,
>  		 uint16_t queue_id);
> 
> +/**
> + * @internal
> + * Setup eth fast-path API to ethdev values.
> + *
> + * @param dev
> + *  Pointer to struct rte_eth_dev.
> + */
> +__rte_internal
> +void rte_eth_fp_ops_setup(struct rte_eth_dev *dev);
> +
>  /**
>   * @internal
>   * Atomically set the link status for the specific device.
> diff --git a/lib/ethdev/rte_ethdev.h b/lib/ethdev/rte_ethdev.h
> index 049641d57c..44ee7229c1 100644
> --- a/lib/ethdev/rte_ethdev.h
> +++ b/lib/ethdev/rte_ethdev.h
> @@ -3944,25 +3944,28 @@ enum rte_eth_event_type {
>  	 */
>  	RTE_ETH_EVENT_RX_AVAIL_THRESH,
>  	/** Port recovering from a hardware or firmware error.
> -	 * If PMD supports proactive error recovery,
> -	 * it should trigger this event to notify application
> -	 * that it detected an error and the recovery is being started.
> -	 * Upon receiving the event, the application should not invoke any control path API
> -	 * (such as rte_eth_dev_configure/rte_eth_dev_stop...) until receiving
> -	 * RTE_ETH_EVENT_RECOVERY_SUCCESS or RTE_ETH_EVENT_RECOVERY_FAILED event.
> -	 * The PMD will set the data path pointers to dummy functions,
> -	 * and re-set the data path pointers to non-dummy functions
> -	 * before reporting RTE_ETH_EVENT_RECOVERY_SUCCESS event.
> -	 * It means that the application cannot send or receive any packets
> -	 * during this period.
> +	 *
> +	 * If PMD supports proactive error recovery, it should trigger this
> +	 * event to notify application that it detected an error and the
> +	 * recovery is about to start.
> +	 *
> +	 * Upon receiving the event, the application should not invoke any
> +	 * control and data path API until receiving
> +	 * RTE_ETH_EVENT_RECOVERY_SUCCESS or RTE_ETH_EVENT_RECOVERY_FAILED
> +	 * event.
> +	 *
> +	 * Once this event is reported, the PMD will set the data path pointers
> +	 * to dummy functions, and re-set the data path pointers to valid
> +	 * functions before reporting RTE_ETH_EVENT_RECOVERY_SUCCESS event.
> +	 *
>  	 * @note Before the PMD reports the recovery result,
>  	 * the PMD may report the RTE_ETH_EVENT_ERR_RECOVERING event again,
>  	 * because a larger error may occur during the recovery.
>  	 */
>  	RTE_ETH_EVENT_ERR_RECOVERING,
>  	/** Port recovers successfully from the error.
> -	 * The PMD already re-configured the port,
> -	 * and the effect is the same as a restart operation.
> +	 *
> +	 * The PMD already re-configured the port:
>  	 * a) The following operation will be retained: (alphabetically)
>  	 *    - DCB configuration
>  	 *    - FEC configuration
> @@ -3989,6 +3992,9 @@ enum rte_eth_event_type {
>  	 *      (@see RTE_ETH_DEV_CAPA_FLOW_SHARED_OBJECT_KEEP)
>  	 * c) Any other configuration will not be stored
>  	 *    and will need to be re-configured.
> +	 *
> +	 * The application should restore some additional configuration
> +	 * (see above case b/c), and then enable data path API invocation.
>  	 */
>  	RTE_ETH_EVENT_RECOVERY_SUCCESS,
>  	/** Port recovery failed.
> diff --git a/lib/ethdev/version.map b/lib/ethdev/version.map
> index 357d1a88c0..c273e0bdae 100644
> --- a/lib/ethdev/version.map
> +++ b/lib/ethdev/version.map
> @@ -320,6 +320,7 @@ INTERNAL {
>  	rte_eth_devices;
>  	rte_eth_dma_zone_free;
>  	rte_eth_dma_zone_reserve;
> +	rte_eth_fp_ops_setup;
>  	rte_eth_hairpin_queue_peer_bind;
>  	rte_eth_hairpin_queue_peer_unbind;
>  	rte_eth_hairpin_queue_peer_update;
> --
 
Acked-by: Konstantin Ananyev <konstantin.ananyev@huawei.com>

> 2.17.1