Re: [dpdk-dev] [RFC v3] ethdev: claim device reset as async

[Ferruh Yigit <ferruh.yigit@intel.com>]

On 3/19/2019 1:40 PM, Zhang, Qi Z wrote:
> 
> 
>> -----Original Message-----
>> From: Yigit, Ferruh
>> Sent: Tuesday, March 19, 2019 9:14 PM
>> To: Zhang, Qi Z <qi.z.zhang@intel.com>; thomas@monjalon.net; Doherty, Declan
>> <declan.doherty@intel.com>
>> Cc: ktraynor@redhat.com; dev@dpdk.org; Shelton, Benjamin H
>> <benjamin.h.shelton@intel.com>; Vangati, Narender
>> <narender.vangati@intel.com>
>> Subject: Re: [RFC v3] ethdev: claim device reset as async
>>
>> On 10/4/2018 4:58 PM, Zhang, Qi Z wrote:
>>>
>>>
>>>> -----Original Message-----
>>>> From: Yigit, Ferruh
>>>> Sent: Thursday, October 4, 2018 7:30 PM
>>>> To: Zhang, Qi Z <qi.z.zhang@intel.com>; thomas@monjalon.net; Doherty,
>>>> Declan <declan.doherty@intel.com>
>>>> Cc: ktraynor@redhat.com; dev@dpdk.org; Shelton, Benjamin H
>>>> <benjamin.h.shelton@intel.com>; Vangati, Narender
>>>> <narender.vangati@intel.com>
>>>> Subject: Re: [RFC v3] ethdev: claim device reset as async
>>>>
>>>> On 9/20/2018 5:56 AM, Qi Zhang wrote:
>>>>> Device reset should be implemented in an async way since it is
>>>>> possible to be invoked in interrupt thread and sometimes to reset a
>>>>> device need to wait for some dependency, for example, a VF expects
>>>>> for PF ready or a NIC function as part of a SOC wait for the whole
>>>>> system reset complete, and all these time-consuming tasks will block
>>>>> the interrupt thread.
>>>>> The patch rename rte_eth_dev_reset to rte_eth_dev_reset_async and
>>>>> rework the implementation. It will spawn a new thread which will
>>>>> call
>>>>> ops->dev_reset, and when finished it will raise the event
>>>>> RTE_ETH_EVENT_RESET_COMPLETE. The application should always wait for
>>>>> this event before it continues to configure and restart the device.
>>>>>
>>>>> Signed-off-by: Qi Zhang <qi.z.zhang@intel.com>
>>>>
>>>> <...>
>>>>
>>>>> @@ -1385,10 +1413,26 @@ rte_eth_dev_reset(uint16_t port_id)
>>>>>
>>>>>  	RTE_FUNC_PTR_OR_ERR_RET(*dev->dev_ops->dev_reset,
>> -ENOTSUP);
>>>>>
>>>>> +	/* already on resetting */
>>>>> +	if (dev->state == RTE_ETH_DEV_RESETTING)
>>>>> +		return 0;
>>>>> +
>>>>> +	args = calloc(1, sizeof(struct dev_reset_args));
>>>>> +	if (!args)
>>>>> +		return -ENOMEM;
>>>>> +
>>>>>  	rte_eth_dev_stop(port_id);
>>>>> -	ret = dev->dev_ops->dev_reset(dev);
>>>>>
>>>>> -	return eth_err(port_id, ret);
>>>>> +	/* store previous device state temporary */
>>>>> +	args->pre_state = dev->state;
>>>>> +
>>>>> +	dev->state = RTE_ETH_DEV_RESETTING;
>>>>
>>>> Do we need to update the state, I think this will break
>>>> rte_eth_dev_count() and friends, like during device reset app will think it has
>> one less device in system.
>>>
>>> I'd like to have this new state which represent the situation of the device more
>> accurate.
>>> In this patch RTE_ETH_DEV_RESETTING is just to be used to prevent double
>> reset, but in future it can also be used to prevent invalid operation during device
>> reset.
>>>
>>> Of cause we need to make sure it does not break exist behavior and seems add
>> RTE_ETH_DEV_RESETTING check in rte_eth_find_next_owned_by and
>> rte_eth_find_next is able to fix the issue you observed.
>>>
>>> I can add this in v4 if you agree the idea.
>>>
>>>>
>>>> <...>
>>>>
>>>>> @@ -1814,21 +1816,29 @@ void rte_eth_dev_close(uint16_t port_id);
>>>>>   * RTE_ETH_EVENT_INTR_RESET event is detected, but can also use it
>>>>> to
>>>> start
>>>>>   * a port reset in other circumstances.
>>>>>   *
>>>>> - * When this function is called, it first stops the port and then
>>>>> calls the
>>>>> - * PMD specific dev_uninit( ) and dev_init( ) to return the port to
>>>>> initial
>>>>> - * state, in which no Tx and Rx queues are setup, as if the port
>>>>> has been
>>>>> - * reset and not started. The port keeps the port id it had before
>>>>> the
>>>>> - * function call.
>>>>> - *
>>>>> - * After calling rte_eth_dev_reset( ), the application should use
>>>>> - * rte_eth_dev_configure( ), rte_eth_rx_queue_setup( ),
>>>>> - * rte_eth_tx_queue_setup( ), and rte_eth_dev_start( )
>>>>> - * to reconfigure the device as appropriate.
>>>>> - *
>>>>> - * Note: To avoid unexpected behavior, the application should stop
>>>>> calling
>>>>> - * Tx and Rx functions before calling rte_eth_dev_reset( ). For
>>>>> thread
>>>>> - * safety, all these controlling functions should be called from
>>>>> the same
>>>>> - * thread.
>>>>> + * @note
>>>>> + * Device reset may have the dependency, for example, a VF reset
>>>>> + expects
>>>>> + * PF ready, or a NIC function as a part of a SOC need to wait for
>>>>> + other
>>>>> + * parts of the system be ready, these are time-consuming tasks and
>>>>> + will
>>>>> + * block current thread.
>>>>> + *
>>>>> + * As the name, rte_eth_dev_reset_async is an async API, it will
>>>>> + spwan a
>>>>> + * new thread to call ops->dev_reset, once it is finished, it will
>>>>> + raise
>>>>> + * the RTE_ETH_EVENT_RESET_COMPLETE event to notify application.
>>>>> + That makes
>>>>> + * things easy for an application that what to reset the device
>>>>> + from the
>>>>> + * interrupt thread since typically a RTE_ETH_EVENT_INTR_RESET
>>>>> + handler is
>>>>> + * invoked in interrupt thread.
>>>>
>>>> thread calls dev_ops->dev_reset(dev) and wait for it, so it means
>>>> dev_ops->dev_reset is synchronous, perhaps it would be good to
>>>> highlight this in "dev_reset" comment to help PMD developers.
>>>
>>> OK
>>>
>>>>
>>>> of dev_ops->dev_reset() is synchronous, means existing
>>>> rte_eth_dev_reset() is synchronous, so what do you thinks keep
>>>> rte_eth_dev_reset() as it is and add new
>>>> rte_eth_dev_reset_async() API? Than we will have both sync and async
>>>> solution.
>>>
>>> Typically device reset happens when application receive
>> RTE_ETH_EVENT_INTR_RESET and this is in interrupt thread.
>>> Invoke an async API in interrupt thread is the right way, is it better if we
>> highlight this is the only way?
>>> I may not prefer to expose the sync API right now, it's better to figure out some
>> typical usage before we expose this, but so far I don't have.
>>
>> Hi Qi,
>>
>> Is the 'rte_eth_dev_reset_async()' still required? Is there any update planned to
>> this RFC?
> 
> Yes, I think the requirement is still there. Just don't have bandwidth work on this recently.
> May I send out v1 for 19.05 in this week? since deprecation notes already be send out in 19.02 cycle

I think technically yes, since proposal is already out for a long time.
But it will give less time to review it when you send this week.

> 
> 
>>
>>>
>>> Regards
>>> Qi
>>>
>>>
>>>>
>>>>> + *
>>>>> + * Application should not assume device reset is finished after
>>>>> + * rte_eth_dev_reset_async return, it should always wait for a
>>>>> + * RTE_ETH_EVENT_RESET_COMPLETE event and check the reset result.
>>>>> + * If reset success, application should call rte_eth_dev_configure(
>>>>> + ),
>>>>> + * rte_eth_rx_queue_setup( ), rte_eth_tx_queue_setup( ),
>>>>> + * and rte_eth_dev_start( ) to reconfigure the device as appropriate.
>>>>> + *
>>>>> + * @Note
>>>>> + * To avoid unexpected behavior, the application should stop
>>>>> + calling
>>>>> + * Tx and Rx functions before calling rte_eth_dev_reset_async( ).
>>>>>   *
>>>>>   * @param port_id
>>>>>   *   The port identifier of the Ethernet device.
>>>>> @@ -1837,12 +1847,10 @@ void rte_eth_dev_close(uint16_t port_id);
>>>>>   *   - (0) if successful.
>>>>>   *   - (-EINVAL) if port identifier is invalid.
>>>>>   *   - (-ENOTSUP) if hardware doesn't support this function.
>>>>> - *   - (-EPERM) if not ran from the primary process.
>>>>> - *   - (-EIO) if re-initialisation failed or device is removed.
>>>>>   *   - (-ENOMEM) if the reset failed due to OOM.
>>>>> - *   - (-EAGAIN) if the reset temporarily failed and should be retried later.
>>>>> + *   - (<0) other errors from low level driver.
>>>>>   */
>>>>> -int rte_eth_dev_reset(uint16_t port_id);
>>>>> +int rte_eth_dev_reset_async(uint16_t port_id);
>>>>>
>>>>>  /**
>>>>>   * Enable receipt in promiscuous mode for an Ethernet device.
>>>>> @@ -2574,6 +2582,8 @@ enum rte_eth_event_type {
>>>>>  				/**< queue state event (enabled/disabled) */
>>>>>  	RTE_ETH_EVENT_INTR_RESET,
>>>>>  			/**< reset interrupt event, sent to VF on PF reset */
>>>>> +	RTE_ETH_EVENT_RESET_COMPLETE,
>>>>> +			/**< inform application that reset is completed */
>>>>>  	RTE_ETH_EVENT_VF_MBOX,  /**< message from the VF received by
>> PF
>>>> */
>>>>>  	RTE_ETH_EVENT_MACSEC,   /**< MACsec offload related event */
>>>>>  	RTE_ETH_EVENT_INTR_RMV, /**< device removal event */
>>>>>
>>>
>