Re: [dpdk-dev] [PATCH v3 2/2] ethdev: make rte_flow API thread safe

[Matan Azrad <matan@nvidia.com>]

From: Suanming Mou
> Currently, the rte_flow functions are not defined as thread safe.
> DPDK applications either call the functions in single thread or add locks
> around the functions for the critical section.
> 

Better to write here "or protect any concurrent calling for the rte_flow operations using a lock."

> For PMDs support the flow operations thread safe natively, the redundant
> protection in application hurts the performance of the rte_flow operation
> functions.
> 
> And the restriction of thread safe not guaranteed for the rte_flow functions

not => is not

> also limits the applications' expectation.
> 
> This feature is going to change the rte_flow functions to be thread safe. As
> different PMDs have different flow operations, some may support thread
> safe already and others may not. For PMDs don't support flow thread safe
> operation, a new lock is defined in ethdev in order to protects thread unsafe
> PMDs from rte_flow level.
> 
> A new RTE_ETH_DEV_FLOW_OPS_THREAD_SAFE device flag is added to
> determine whether the PMD supports thread safe flow operation or not.
> For PMDs support thread safe flow operations, set the
> RTE_ETH_DEV_FLOW_OPS_THREAD_SAFE flag, rte_flow level functions will
> skip the thread safe helper lock for these PMDs. Again the rte_flow level
> thread safe lock only works when PMD operation functions are not thread
> safe.
> 
> For the PMDs which don't want the default mutex lock, just set the flag in
> the PMD, and add the prefer type of lock in the PMD. Then the default
> mutex lock is easily replaced by the PMD level lock.
> 
> The change has no effect on the current DPDK applications. No change is
> required for the current DPDK applications. For the standard posix
> pthread_mutex, if no lock contention with the added rte_flow level mutex,
> the mutex only does the atomic increasing in
> pthread_mutex_lock() and decreasing in
> pthread_mutex_unlock(). No futex() syscall will be involved.
> 
> Signed-off-by: Suanming Mou <suanmingm@nvidia.com>
> ---
> 
> v3:
>  - update flow_lock/unlock -> fts_enter/exit
> 
> v2:
>  - Update commit info and description doc.
>  - Add inline for the flow lock and unlock functions.
>  - Remove the PMD sample part flag configuration.
> 
> ---
> 
>  doc/guides/prog_guide/rte_flow.rst  |  9 ++--
>  lib/librte_ethdev/rte_ethdev.c      |  2 +
>  lib/librte_ethdev/rte_ethdev.h      |  2 +
>  lib/librte_ethdev/rte_ethdev_core.h |  4 ++
>  lib/librte_ethdev/rte_flow.c        | 84 ++++++++++++++++++++++++++++---
> ------
>  5 files changed, 78 insertions(+), 23 deletions(-)
> 
> diff --git a/doc/guides/prog_guide/rte_flow.rst
> b/doc/guides/prog_guide/rte_flow.rst
> index 119b128..ae2ddb3 100644
> --- a/doc/guides/prog_guide/rte_flow.rst
> +++ b/doc/guides/prog_guide/rte_flow.rst
> @@ -3046,10 +3046,6 @@ Caveats
>  - API operations are synchronous and blocking (``EAGAIN`` cannot be
>    returned).
> 
> -- There is no provision for re-entrancy/multi-thread safety, although nothing
> -  should prevent different devices from being configured at the same
> -  time. PMDs may protect their control path functions accordingly.
> -
>  - Stopping the data path (TX/RX) should not be necessary when managing
> flow
>    rules. If this cannot be achieved naturally or with workarounds (such as
>    temporarily replacing the burst function pointers), an appropriate error @@
> -3101,6 +3097,11 @@ This interface additionally defines the following helper
> function:
>  - ``rte_flow_ops_get()``: get generic flow operations structure from a
>    port.
> 
> +If PMD interfaces do not support re-entrancy/multi-thread safety,
> +rte_flow level functions will do it by mutex. The application can test

Good to mention mutex per port.

> +the dev_flags with RTE_ETH_DEV_FLOW_OPS_THREAD_SAFE in struct
> +rte_eth_dev_data to know if the rte_flow thread-safe works under
> rte_flow level or PMD level.
> +

If think it will be helpful to add here a note saying that it is unsafe to call other control commands In parallel to rte_flow operations. 

>  More will be added over time.
> 
>  Device compatibility
> diff --git a/lib/librte_ethdev/rte_ethdev.c b/lib/librte_ethdev/rte_ethdev.c
> index 0f56541..60677fe 100644
> --- a/lib/librte_ethdev/rte_ethdev.c
> +++ b/lib/librte_ethdev/rte_ethdev.c
> @@ -500,6 +500,7 @@ struct rte_eth_dev *
>  	strlcpy(eth_dev->data->name, name, sizeof(eth_dev->data-
> >name));
>  	eth_dev->data->port_id = port_id;
>  	eth_dev->data->mtu = RTE_ETHER_MTU;
> +	pthread_mutex_init(&eth_dev->data->fts_mutex, NULL);
> 
>  unlock:
>  	rte_spinlock_unlock(&rte_eth_dev_shared_data->ownership_lock);
> @@ -564,6 +565,7 @@ struct rte_eth_dev *
>  		rte_free(eth_dev->data->mac_addrs);
>  		rte_free(eth_dev->data->hash_mac_addrs);
>  		rte_free(eth_dev->data->dev_private);
> +		pthread_mutex_destroy(&eth_dev->data->fts_mutex);
>  		memset(eth_dev->data, 0, sizeof(struct
> rte_eth_dev_data));
>  	}
> 
> diff --git a/lib/librte_ethdev/rte_ethdev.h b/lib/librte_ethdev/rte_ethdev.h
> index d2bf74f..03612fd 100644
> --- a/lib/librte_ethdev/rte_ethdev.h
> +++ b/lib/librte_ethdev/rte_ethdev.h
> @@ -1664,6 +1664,8 @@ struct rte_eth_dev_owner {  #define
> RTE_ETH_DEV_REPRESENTOR  0x0010
>  /** Device does not support MAC change after started */  #define
> RTE_ETH_DEV_NOLIVE_MAC_ADDR  0x0020
> +/** Device PMD supports thread safety flow operation */ #define
> +RTE_ETH_DEV_FLOW_OPS_THREAD_SAFE  0x0040
> 
>  /**
>   * Iterates over valid ethdev ports owned by a specific owner.
> diff --git a/lib/librte_ethdev/rte_ethdev_core.h
> b/lib/librte_ethdev/rte_ethdev_core.h
> index fd3bf92..89df65a 100644
> --- a/lib/librte_ethdev/rte_ethdev_core.h
> +++ b/lib/librte_ethdev/rte_ethdev_core.h
> @@ -5,6 +5,9 @@
>  #ifndef _RTE_ETHDEV_CORE_H_
>  #define _RTE_ETHDEV_CORE_H_
> 
> +#include <pthread.h>
> +#include <sys/types.h>
> +
>  /**
>   * @file
>   *
> @@ -180,6 +183,7 @@ struct rte_eth_dev_data {
>  			 *   Valid if RTE_ETH_DEV_REPRESENTOR in dev_flags.
>  			 */
> 
> +	pthread_mutex_t fts_mutex; /**< rte flow ops thread safety mutex.
> */
>  	uint64_t reserved_64s[4]; /**< Reserved for future fields */
>  	void *reserved_ptrs[4];   /**< Reserved for future fields */
>  } __rte_cache_aligned;
> diff --git a/lib/librte_ethdev/rte_flow.c b/lib/librte_ethdev/rte_flow.c index
> f8fdd68..6823458 100644
> --- a/lib/librte_ethdev/rte_flow.c
> +++ b/lib/librte_ethdev/rte_flow.c
> @@ -207,6 +207,20 @@ struct rte_flow_desc_data {
>  	return -rte_errno;
>  }
> 
> +static inline void
> +fts_enter(struct rte_eth_dev *dev)
> +{
> +	if (!(dev->data->dev_flags &
> RTE_ETH_DEV_FLOW_OPS_THREAD_SAFE))
> +		pthread_mutex_lock(&dev->data->fts_mutex);
> +}
> +
> +static inline void
> +fts_exit(struct rte_eth_dev *dev)
> +{
> +	if (!(dev->data->dev_flags &
> RTE_ETH_DEV_FLOW_OPS_THREAD_SAFE))
> +		pthread_mutex_unlock(&dev->data->fts_mutex);
> +}
> +
>  static int
>  flow_err(uint16_t port_id, int ret, struct rte_flow_error *error)  { @@ -
> 346,12 +360,16 @@ struct rte_flow_desc_data {  {
>  	const struct rte_flow_ops *ops = rte_flow_ops_get(port_id, error);
>  	struct rte_eth_dev *dev = &rte_eth_devices[port_id];
> +	int ret;
> 
>  	if (unlikely(!ops))
>  		return -rte_errno;
> -	if (likely(!!ops->validate))
> -		return flow_err(port_id, ops->validate(dev, attr, pattern,
> -						       actions, error), error);
> +	if (likely(!!ops->validate)) {
> +		fts_enter(dev);
> +		ret = ops->validate(dev, attr, pattern, actions, error);
> +		fts_exit(dev);
> +		return flow_err(port_id, ret, error);
> +	}
>  	return rte_flow_error_set(error, ENOSYS,
>  				  RTE_FLOW_ERROR_TYPE_UNSPECIFIED,
>  				  NULL, rte_strerror(ENOSYS));
> @@ -372,7 +390,9 @@ struct rte_flow *
>  	if (unlikely(!ops))
>  		return NULL;
>  	if (likely(!!ops->create)) {
> +		fts_enter(dev);
>  		flow = ops->create(dev, attr, pattern, actions, error);
> +		fts_exit(dev);
>  		if (flow == NULL)
>  			flow_err(port_id, -rte_errno, error);
>  		return flow;
> @@ -390,12 +410,16 @@ struct rte_flow *
>  {
>  	struct rte_eth_dev *dev = &rte_eth_devices[port_id];
>  	const struct rte_flow_ops *ops = rte_flow_ops_get(port_id, error);
> +	int ret;
> 
>  	if (unlikely(!ops))
>  		return -rte_errno;
> -	if (likely(!!ops->destroy))
> -		return flow_err(port_id, ops->destroy(dev, flow, error),
> -				error);
> +	if (likely(!!ops->destroy)) {
> +		fts_enter(dev);
> +		ret = ops->destroy(dev, flow, error);
> +		fts_exit(dev);
> +		return flow_err(port_id, ret, error);
> +	}
>  	return rte_flow_error_set(error, ENOSYS,
>  				  RTE_FLOW_ERROR_TYPE_UNSPECIFIED,
>  				  NULL, rte_strerror(ENOSYS));
> @@ -408,11 +432,16 @@ struct rte_flow *
>  {
>  	struct rte_eth_dev *dev = &rte_eth_devices[port_id];
>  	const struct rte_flow_ops *ops = rte_flow_ops_get(port_id, error);
> +	int ret;
> 
>  	if (unlikely(!ops))
>  		return -rte_errno;
> -	if (likely(!!ops->flush))
> -		return flow_err(port_id, ops->flush(dev, error), error);
> +	if (likely(!!ops->flush)) {
> +		fts_enter(dev);
> +		ret = ops->flush(dev, error);
> +		fts_exit(dev);
> +		return flow_err(port_id, ret, error);
> +	}
>  	return rte_flow_error_set(error, ENOSYS,
>  				  RTE_FLOW_ERROR_TYPE_UNSPECIFIED,
>  				  NULL, rte_strerror(ENOSYS));
> @@ -428,12 +457,16 @@ struct rte_flow *
>  {
>  	struct rte_eth_dev *dev = &rte_eth_devices[port_id];
>  	const struct rte_flow_ops *ops = rte_flow_ops_get(port_id, error);
> +	int ret;
> 
>  	if (!ops)
>  		return -rte_errno;
> -	if (likely(!!ops->query))
> -		return flow_err(port_id, ops->query(dev, flow, action, data,
> -						    error), error);
> +	if (likely(!!ops->query)) {
> +		fts_enter(dev);
> +		ret = ops->query(dev, flow, action, data, error);
> +		fts_exit(dev);
> +		return flow_err(port_id, ret, error);
> +	}
>  	return rte_flow_error_set(error, ENOSYS,
>  				  RTE_FLOW_ERROR_TYPE_UNSPECIFIED,
>  				  NULL, rte_strerror(ENOSYS));
> @@ -447,11 +480,16 @@ struct rte_flow *
>  {
>  	struct rte_eth_dev *dev = &rte_eth_devices[port_id];
>  	const struct rte_flow_ops *ops = rte_flow_ops_get(port_id, error);
> +	int ret;
> 
>  	if (!ops)
>  		return -rte_errno;
> -	if (likely(!!ops->isolate))
> -		return flow_err(port_id, ops->isolate(dev, set, error), error);
> +	if (likely(!!ops->isolate)) {
> +		fts_enter(dev);
> +		ret = ops->isolate(dev, set, error);
> +		fts_exit(dev);
> +		return flow_err(port_id, ret, error);
> +	}
>  	return rte_flow_error_set(error, ENOSYS,
>  				  RTE_FLOW_ERROR_TYPE_UNSPECIFIED,
>  				  NULL, rte_strerror(ENOSYS));
> @@ -1224,12 +1262,16 @@ enum rte_flow_conv_item_spec_type {  {
>  	struct rte_eth_dev *dev = &rte_eth_devices[port_id];
>  	const struct rte_flow_ops *ops = rte_flow_ops_get(port_id, error);
> +	int ret;
> 
>  	if (unlikely(!ops))
>  		return -rte_errno;
> -	if (likely(!!ops->dev_dump))
> -		return flow_err(port_id, ops->dev_dump(dev, file, error),
> -				error);
> +	if (likely(!!ops->dev_dump)) {
> +		fts_enter(dev);
> +		ret = ops->dev_dump(dev, file, error);
> +		fts_exit(dev);
> +		return flow_err(port_id, ret, error);
> +	}
>  	return rte_flow_error_set(error, ENOSYS,
>  				  RTE_FLOW_ERROR_TYPE_UNSPECIFIED,
>  				  NULL, rte_strerror(ENOSYS));
> @@ -1241,12 +1283,16 @@ enum rte_flow_conv_item_spec_type {  {
>  	struct rte_eth_dev *dev = &rte_eth_devices[port_id];
>  	const struct rte_flow_ops *ops = rte_flow_ops_get(port_id, error);
> +	int ret;
> 
>  	if (unlikely(!ops))
>  		return -rte_errno;
> -	if (likely(!!ops->get_aged_flows))
> -		return flow_err(port_id, ops->get_aged_flows(dev,
> contexts,
> -				nb_contexts, error), error);
> +	if (likely(!!ops->get_aged_flows)) {
> +		fts_enter(dev);
> +		ret = ops->get_aged_flows(dev, contexts, nb_contexts,
> error);
> +		fts_exit(dev);
> +		return flow_err(port_id, ret, error);
> +	}
>  	return rte_flow_error_set(error, ENOTSUP,
>  				  RTE_FLOW_ERROR_TYPE_UNSPECIFIED,
>  				  NULL, rte_strerror(ENOTSUP));
> --
> 1.8.3.1

Besides the above (not must) suggestion, looks good,
Acked-by: Matan Azrad <matan@nvidia.com>