[dpdk-dev] [PATCH V18 2/4] eal: add device event monitor framework

Tan, Jianfeng jianfeng.tan at intel.com
Wed Apr 4 04:53:15 CEST 2018



> -----Original Message-----
> From: Guo, Jia
> Sent: Tuesday, April 3, 2018 6:34 PM
> To: stephen at networkplumber.org; Richardson, Bruce; Yigit, Ferruh;
> Ananyev, Konstantin; gaetan.rivet at 6wind.com; Wu, Jingjing;
> thomas at monjalon.net; motih at mellanox.com; Van Haaren, Harry; Tan,
> Jianfeng
> Cc: jblunck at infradead.org; shreyansh.jain at nxp.com; dev at dpdk.org; Guo,
> Jia; Zhang, Helin
> Subject: [PATCH V18 2/4] eal: add device event monitor framework
> 
> This patch aims to add a general device event monitor framework at
> EAL device layer, for device hotplug awareness and actions adopted
> accordingly. It could also expand for all other types of device event
> monitor, but not in this scope at the stage.
> 
> To get started, users firstly call below new added APIs to enable/disable
> the device event monitor mechanism:
>   - rte_dev_event_monitor_start
>   - rte_dev_event_monitor_stop
> 
> Then users shell register or unregister callbacks through the new added
> APIs. Callbacks can be some device specific, or for all devices.
>   -rte_dev_event_callback_register
>   -rte_dev_event_callback_unregister
> 
> Use hotplug case for example, when device hotplug insertion or hotplug
> removal, we will get notified from kernel, then call user's callbacks
> accordingly to handle it, such as detach or attach the device from the
> bus, and could benefit further fail-safe or live-migration.
> 
> Signed-off-by: Jeff Guo <jia.guo at intel.com>
> ---
> v18->v17:
> add feature announcement in release document, fix bsp compile issue.
> ---
>  doc/guides/rel_notes/release_18_05.rst  |   9 ++
>  lib/librte_eal/bsdapp/eal/Makefile      |   1 +
>  lib/librte_eal/bsdapp/eal/eal_dev.c     |  21 ++++
>  lib/librte_eal/bsdapp/eal/meson.build   |   1 +
>  lib/librte_eal/common/eal_common_dev.c  | 168
> ++++++++++++++++++++++++++++++++
>  lib/librte_eal/common/eal_private.h     |  15 +++
>  lib/librte_eal/common/include/rte_dev.h |  94 ++++++++++++++++++
>  lib/librte_eal/linuxapp/eal/Makefile    |   1 +
>  lib/librte_eal/linuxapp/eal/eal_dev.c   |  22 +++++
>  lib/librte_eal/linuxapp/eal/meson.build |   1 +
>  lib/librte_eal/rte_eal_version.map      |   8 ++
>  11 files changed, 341 insertions(+)
>  create mode 100644 lib/librte_eal/bsdapp/eal/eal_dev.c
>  create mode 100644 lib/librte_eal/linuxapp/eal/eal_dev.c
> 
> diff --git a/doc/guides/rel_notes/release_18_05.rst
> b/doc/guides/rel_notes/release_18_05.rst
> index 3923dc2..37e00c4 100644
> --- a/doc/guides/rel_notes/release_18_05.rst
> +++ b/doc/guides/rel_notes/release_18_05.rst
> @@ -41,6 +41,15 @@ New Features
>       Also, make sure to start the actual text at the margin.
> 
> =========================================================
> 
> +* **Added device event monitor framework.**
> +
> +  Added a general device event monitor framework at EAL, for device
> dynamic management.
> +  Such as device hotplug awareness and actions adopted accordingly. The list
> of new APIs:
> +
> +  * ``rte_dev_event_monitor_start`` and ``rte_dev_event_monitor_stop``
> are for
> +    the event monitor enable and disable.
> +  * ``rte_dev_event_callback_register`` and
> ``rte_dev_event_callback_unregister``
> +    are for the user's callbacks register and unregister.
> 
>  API Changes
>  -----------
> diff --git a/lib/librte_eal/bsdapp/eal/Makefile
> b/lib/librte_eal/bsdapp/eal/Makefile
> index dd455e6..c0921dd 100644
> --- a/lib/librte_eal/bsdapp/eal/Makefile
> +++ b/lib/librte_eal/bsdapp/eal/Makefile
> @@ -33,6 +33,7 @@ SRCS-$(CONFIG_RTE_EXEC_ENV_BSDAPP) +=
> eal_lcore.c
>  SRCS-$(CONFIG_RTE_EXEC_ENV_BSDAPP) += eal_timer.c
>  SRCS-$(CONFIG_RTE_EXEC_ENV_BSDAPP) += eal_interrupts.c
>  SRCS-$(CONFIG_RTE_EXEC_ENV_BSDAPP) += eal_alarm.c
> +SRCS-$(CONFIG_RTE_EXEC_ENV_BSDAPP) += eal_dev.c
> 
>  # from common dir
>  SRCS-$(CONFIG_RTE_EXEC_ENV_BSDAPP) += eal_common_lcore.c
> diff --git a/lib/librte_eal/bsdapp/eal/eal_dev.c
> b/lib/librte_eal/bsdapp/eal/eal_dev.c
> new file mode 100644
> index 0000000..1c6c51b
> --- /dev/null
> +++ b/lib/librte_eal/bsdapp/eal/eal_dev.c
> @@ -0,0 +1,21 @@
> +/* SPDX-License-Identifier: BSD-3-Clause
> + * Copyright(c) 2018 Intel Corporation
> + */
> +
> +#include <rte_log.h>
> +#include <rte_compat.h>
> +#include <rte_dev.h>
> +
> +int __rte_experimental
> +rte_dev_event_monitor_start(void)
> +{
> +	RTE_LOG(ERR, EAL, "Device event is not supported for FreeBSD\n");
> +	return -1;
> +}
> +
> +int __rte_experimental
> +rte_dev_event_monitor_stop(void)
> +{
> +	RTE_LOG(ERR, EAL, "Device event is not supported for FreeBSD\n");
> +	return -1;
> +}
> diff --git a/lib/librte_eal/bsdapp/eal/meson.build
> b/lib/librte_eal/bsdapp/eal/meson.build
> index e83fc91..6dfc533 100644
> --- a/lib/librte_eal/bsdapp/eal/meson.build
> +++ b/lib/librte_eal/bsdapp/eal/meson.build
> @@ -12,4 +12,5 @@ env_sources = files('eal_alarm.c',
>  		'eal_timer.c',
>  		'eal.c',
>  		'eal_memory.c',
> +		'eal_dev.c'
>  )
> diff --git a/lib/librte_eal/common/eal_common_dev.c
> b/lib/librte_eal/common/eal_common_dev.c
> index cd07144..e09e86f 100644
> --- a/lib/librte_eal/common/eal_common_dev.c
> +++ b/lib/librte_eal/common/eal_common_dev.c
> @@ -14,9 +14,34 @@
>  #include <rte_devargs.h>
>  #include <rte_debug.h>
>  #include <rte_log.h>
> +#include <rte_spinlock.h>
> +#include <rte_malloc.h>
> 
>  #include "eal_private.h"
> 
> +/* spinlock for device callbacks */

It's for protect callback list.

> +static rte_spinlock_t dev_event_lock = RTE_SPINLOCK_INITIALIZER;

Put this spinlock where the list locates.

> +
> +/**
> + * The device event callback description.
> + *
> + * It contains callback address to be registered by user application,
> + * the pointer to the parameters for callback, and the device name.
> + */
> +struct dev_event_callback {
> +	TAILQ_ENTRY(dev_event_callback) next; /**< Callbacks list */
> +	rte_dev_event_cb_fn cb_fn;                /**< Callback address */
> +	void *cb_arg;                           /**< Callback parameter */
> +	char *dev_name;	 /**< Callback device name, NULL is for all
> device */
> +	uint32_t active;                        /**< Callback is executing */
> +};
> +
> +/** @internal Structure to keep track of registered callbacks */
> +TAILQ_HEAD(dev_event_cb_list, dev_event_callback);
> +
> +/* The device event callback list for all registered callbacks. */
> +static struct dev_event_cb_list dev_event_cbs;
> +
>  static int cmp_detached_dev_name(const struct rte_device *dev,
>  	const void *_name)
>  {
> @@ -207,3 +232,146 @@ rte_eal_hotplug_remove(const char *busname,
> const char *devname)
>  	rte_eal_devargs_remove(busname, devname);
>  	return ret;
>  }
> +
> +int __rte_experimental
> +rte_dev_event_callback_register(const char *device_name,
> +				rte_dev_event_cb_fn cb_fn,
> +				void *cb_arg)
> +{
> +	struct dev_event_callback *event_cb;
> +	int ret;
> +
> +	if (!cb_fn)
> +		return -EINVAL;
> +
> +	rte_spinlock_lock(&dev_event_lock);
> +
> +	if (TAILQ_EMPTY(&dev_event_cbs))
> +		TAILQ_INIT(&dev_event_cbs);
> +
> +	TAILQ_FOREACH(event_cb, &dev_event_cbs, next) {
> +		if (event_cb->cb_fn == cb_fn && event_cb->cb_arg ==
> cb_arg) {
> +			if (device_name == NULL && event_cb->dev_name
> == NULL)
> +				break;
> +			if (device_name == NULL || event_cb->dev_name
> == NULL)
> +				continue;
> +			if (!strcmp(event_cb->dev_name, device_name))
> +				break;
> +		}
> +	}
> +
> +	/* create a new callback. */
> +	if (event_cb == NULL) {
> +		event_cb = malloc(sizeof(struct dev_event_callback));
> +		if (event_cb != NULL) {
> +			event_cb->cb_fn = cb_fn;
> +			event_cb->cb_arg = cb_arg;
> +			event_cb->active = 0;
> +			if (!device_name) {
> +				event_cb->dev_name = NULL;
> +			} else {
> +				event_cb->dev_name =
> strdup(device_name);
> +				if (event_cb->dev_name == NULL) {
> +					ret = -ENOMEM;
> +					goto error;
> +				}
> +			}
> +			TAILQ_INSERT_TAIL(&dev_event_cbs, event_cb,
> next);
> +		} else {
> +			RTE_LOG(ERR, EAL,
> +				"Failed to allocate memory for device "
> +				"event callback.");
> +			ret = -ENOMEM;
> +			goto error;
> +		}
> +	} else {
> +		RTE_LOG(ERR, EAL,
> +			"The callback is already exist, no need "
> +			"to register again.\n");
> +		ret = -EEXIST;
> +		goto error;

Here is a bug that you will free an existing callback entry.

> +	}
> +
> +	rte_spinlock_unlock(&dev_event_lock);
> +	return 0;
> +error:
> +	free(event_cb);
> +	rte_spinlock_unlock(&dev_event_lock);
> +	return ret;
> +}
> +
> +int __rte_experimental
> +rte_dev_event_callback_unregister(const char *device_name,
> +				  rte_dev_event_cb_fn cb_fn,
> +				  void *cb_arg)
> +{

Let's clearly define the behavior and return of this API. If I understand it correctly,

    If cb_arg != -1, we use (dev_name, cb_fn, cb_arg) as the key to look up the registered API.
    If cb_arg == -1, we use (cb_fn) as the key to look up the registered API.

For return value, we want to return the number of callbacks being removed. It could be:
  >=0, number of callbacks been removed. (When we encounter an active callback, we shall skip it or just return -EAGAIN, neither sounds good to me actually)
 <0, error encountered.

If you agree with above statement, below implementation has lots of issues.

> +	int ret = 0;
> +	struct dev_event_callback *event_cb, *next;
> +
> +	if (!cb_fn)
> +		return -EINVAL;
> +
> +	rte_spinlock_lock(&dev_event_lock);
> +
> +	/*walk through the callbacks and remove all that match. */
> +	for (event_cb = TAILQ_FIRST(&dev_event_cbs); event_cb != NULL;
> +	     event_cb = next) {
> +
> +		next = TAILQ_NEXT(event_cb, next);

First of all, if cb_fn  != event_cb->cb_fn, we shall continue.

> +
> +		if (device_name != NULL && event_cb->dev_name != NULL) {
> +			if (!strcmp(event_cb->dev_name, device_name)) {
> +				if (event_cb->cb_fn != cb_fn ||
> +				    (cb_arg != (void *)-1 &&
> +				    event_cb->cb_arg != cb_arg))
> +					continue;
> +			}
> +		} else if (device_name != NULL) {
> +			continue;
> +		}

What about device_name == NULL && event_cb->dev_name != NULL && cb_arg == -1?

What about device_name == NULL && event_cb->dev_name == NULL &&  cb_arg != -1 && cb_arg != event_cb->cb_arg?


> +
> +		/*
> +		 * if this callback is not executing right now,
> +		 * then remove it.
> +		 */
> +		if (event_cb->active == 0) {
> +			TAILQ_REMOVE(&dev_event_cbs, event_cb, next);
> +			free(event_cb);
> +			ret++;
> +		} else {
> +			ret = -EAGAIN;

If you don't break here, next time you find another satisfied callback, you will ret++ on a (-EAGAIN) value.

> +		}
> +	}
> +	rte_spinlock_unlock(&dev_event_lock);
> +	return ret;
> +}

BTW, don't know why DPDK has the tradition of using cb_arg==-1 to stand for multiple callbacks, it's not a good API design to me. Would like as others' opinions, shall we continue this?

> +
> +void
> +dev_callback_process(char *device_name, enum rte_dev_event_type
> event)
> +{
> +	struct dev_event_callback *cb_lst;
> +	int rc;
> +
> +	if (device_name == NULL)
> +		return;
> +
> +	rte_spinlock_lock(&dev_event_lock);
> +
> +	TAILQ_FOREACH(cb_lst, &dev_event_cbs, next) {
> +		if (cb_lst->dev_name) {
> +			if (strcmp(cb_lst->dev_name, device_name))
> +				continue;
> +		}
> +		cb_lst->active = 1;
> +		rte_spinlock_unlock(&dev_event_lock);
> +		rc = cb_lst->cb_fn(device_name, event,
> +				cb_lst->cb_arg);
> +		if (rc) {
> +			RTE_LOG(ERR, EAL,
> +				"Failed to process callback function.");
> +		}

I don't see a reason why we need the return value from callbacks. Probably, define it as void type.

> +		rte_spinlock_lock(&dev_event_lock);
> +		cb_lst->active = 0;
> +	}
> +	rte_spinlock_unlock(&dev_event_lock);
> +}
> diff --git a/lib/librte_eal/common/eal_private.h
> b/lib/librte_eal/common/eal_private.h
> index 0b28770..88e5a59 100644
> --- a/lib/librte_eal/common/eal_private.h
> +++ b/lib/librte_eal/common/eal_private.h
> @@ -9,6 +9,8 @@
>  #include <stdint.h>
>  #include <stdio.h>
> 
> +#include <rte_dev.h>
> +
>  /**
>   * Initialize the memzone subsystem (private to eal).
>   *
> @@ -205,4 +207,17 @@ struct rte_bus
> *rte_bus_find_by_device_name(const char *str);
> 
>  int rte_mp_channel_init(void);
> 
> +/**
> + * Internal Executes all the user application registered callbacks for
> + * the specific device. It is for DPDK internal user only. User
> + * application should not call it directly.
> + *
> + * @param device_name
> + *  The device name.
> + * @param event
> + *  the device event type.
> + *
> + */
> +void
> +dev_callback_process(char *device_name, enum rte_dev_event_type event);

Too many *_process functions in this patch. Let's avoid using such ambiguous words.

For example, you can rename this function to dev_event_callback_invoke().

>  #endif /* _EAL_PRIVATE_H_ */
> diff --git a/lib/librte_eal/common/include/rte_dev.h
> b/lib/librte_eal/common/include/rte_dev.h
> index b688f1e..4c78938 100644
> --- a/lib/librte_eal/common/include/rte_dev.h
> +++ b/lib/librte_eal/common/include/rte_dev.h
> @@ -24,6 +24,25 @@ extern "C" {
>  #include <rte_compat.h>
>  #include <rte_log.h>
> 
> +/**
> + * The device event type.
> + */
> +enum rte_dev_event_type {
> +	RTE_DEV_EVENT_ADD,	/**< device being added */
> +	RTE_DEV_EVENT_REMOVE,	/**< device being removed */
> +	RTE_DEV_EVENT_MAX	/**< max value of this enum */
> +};
> +
> +struct rte_dev_event {
> +	enum rte_dev_event_type type;	/**< device event type */
> +	int subsystem;			/**< subsystem id */
> +	char *devname;			/**< device name */
> +};
> +
> +typedef int (*rte_dev_event_cb_fn)(char *device_name,
> +					enum rte_dev_event_type event,
> +					void *cb_arg);
> +
>  __attribute__((format(printf, 2, 0)))
>  static inline void
>  rte_pmd_debug_trace(const char *func_name, const char *fmt, ...)
> @@ -267,4 +286,79 @@ __attribute__((used)) = str
>  }
>  #endif
> 
> +/**
> + * @warning
> + * @b EXPERIMENTAL: this API may change without prior notice
> + *
> + * It registers the callback for the specific device.
> + * Multiple callbacks cal be registered at the same time.
> + *
> + * @param device_name
> + *  The device name, that is the param name of the struct rte_device,
> + *  null value means for all devices.
> + * @param cb_fn
> + *  callback address.
> + * @param cb_arg
> + *  address of parameter for callback.
> + *
> + * @return
> + *  - On success, zero.
> + *  - On failure, a negative value.
> + */
> +int __rte_experimental
> +rte_dev_event_callback_register(const char *device_name,
> +				rte_dev_event_cb_fn cb_fn,
> +				void *cb_arg);
> +
> +/**
> + * @warning
> + * @b EXPERIMENTAL: this API may change without prior notice
> + *
> + * It unregisters the callback according to the specified device.
> + *
> + * @param device_name
> + *  The device name, that is the param name of the struct rte_device,
> + *  null value means for all devices.
> + * @param cb_fn
> + *  callback address.
> + * @param cb_arg
> + *  address of parameter for callback, (void *)-1 means to remove all
> + *  registered which has the same callback address.
> + *
> + * @return
> + *  - On success, return the number of callback entities removed.
> + *  - On failure, a negative value.
> + */
> +int __rte_experimental
> +rte_dev_event_callback_unregister(const char *device_name,
> +				  rte_dev_event_cb_fn cb_fn,
> +				  void *cb_arg);
> +
> +/**
> + * @warning
> + * @b EXPERIMENTAL: this API may change without prior notice
> + *
> + * Start the device event monitoring.
> + *
> + * @param none
> + * @return
> + *   - On success, zero.
> + *   - On failure, a negative value.
> + */
> +int __rte_experimental
> +rte_dev_event_monitor_start(void);
> +
> +/**
> + * @warning
> + * @b EXPERIMENTAL: this API may change without prior notice
> + *
> + * Stop the device event monitoring .
> + *
> + * @param none
> + * @return
> + *   - On success, zero.
> + *   - On failure, a negative value.
> + */
> +int __rte_experimental
> +rte_dev_event_monitor_stop(void);
>  #endif /* _RTE_DEV_H_ */
> diff --git a/lib/librte_eal/linuxapp/eal/Makefile
> b/lib/librte_eal/linuxapp/eal/Makefile
> index 7e5bbe8..8578796 100644
> --- a/lib/librte_eal/linuxapp/eal/Makefile
> +++ b/lib/librte_eal/linuxapp/eal/Makefile
> @@ -41,6 +41,7 @@ SRCS-$(CONFIG_RTE_EXEC_ENV_LINUXAPP) +=
> eal_lcore.c
>  SRCS-$(CONFIG_RTE_EXEC_ENV_LINUXAPP) += eal_timer.c
>  SRCS-$(CONFIG_RTE_EXEC_ENV_LINUXAPP) += eal_interrupts.c
>  SRCS-$(CONFIG_RTE_EXEC_ENV_LINUXAPP) += eal_alarm.c
> +SRCS-$(CONFIG_RTE_EXEC_ENV_LINUXAPP) += eal_dev.c
> 
>  # from common dir
>  SRCS-$(CONFIG_RTE_EXEC_ENV_LINUXAPP) += eal_common_lcore.c
> diff --git a/lib/librte_eal/linuxapp/eal/eal_dev.c
> b/lib/librte_eal/linuxapp/eal/eal_dev.c
> new file mode 100644
> index 0000000..9c8d1a0
> --- /dev/null
> +++ b/lib/librte_eal/linuxapp/eal/eal_dev.c
> @@ -0,0 +1,22 @@
> +/* SPDX-License-Identifier: BSD-3-Clause
> + * Copyright(c) 2018 Intel Corporation
> + */
> +
> +#include <rte_log.h>
> +#include <rte_compat.h>
> +#include <rte_dev.h>
> +
> +
> +int __rte_experimental
> +rte_dev_event_monitor_start(void)
> +{
> +	/* TODO: start uevent monitor for linux */
> +	return 0;
> +}
> +
> +int __rte_experimental
> +rte_dev_event_monitor_stop(void)
> +{
> +	/* TODO: stop uevent monitor for linux */
> +	return 0;
> +}
> diff --git a/lib/librte_eal/linuxapp/eal/meson.build
> b/lib/librte_eal/linuxapp/eal/meson.build
> index 03974ff..b222571 100644
> --- a/lib/librte_eal/linuxapp/eal/meson.build
> +++ b/lib/librte_eal/linuxapp/eal/meson.build
> @@ -18,6 +18,7 @@ env_sources = files('eal_alarm.c',
>  		'eal_vfio_mp_sync.c',
>  		'eal.c',
>  		'eal_memory.c',
> +		'eal_dev.c',
>  )
> 
>  if has_libnuma == 1
> diff --git a/lib/librte_eal/rte_eal_version.map
> b/lib/librte_eal/rte_eal_version.map
> index d123602..d23f491 100644
> --- a/lib/librte_eal/rte_eal_version.map
> +++ b/lib/librte_eal/rte_eal_version.map
> @@ -256,3 +256,11 @@ EXPERIMENTAL {
>  	rte_service_start_with_defaults;
> 
>  } DPDK_18.02;
> +
> +EXPERIMENTAL {
> +        global:
> +
> +        rte_dev_event_callback_register;
> +        rte_dev_event_callback_unregister;
> +
> +} DPDK_18.05;
> --
> 2.7.4



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