Re: [dpdk-dev] [PATCH v3 09/15] net/sfc: use new rte_eth_linkstatus functions

[Andrew Rybchenko <arybchenko@solarflare.com>]

On 01/09/2018 07:27 PM, Stephen Hemminger wrote:
> On Tue, 9 Jan 2018 13:35:58 +0300
> Andrew Rybchenko <arybchenko@solarflare.com> wrote:
>
>> On 01/08/2018 08:45 PM, Stephen Hemminger wrote:
>>> Use the new API (_rte_eth_linkstatus_set) to handle link status update.
>>>
>>> Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
>>> ---
>>>    drivers/net/sfc/sfc_ethdev.c | 27 +++++++--------------------
>>>    drivers/net/sfc/sfc_ev.c     | 23 ++++-------------------
>>>    2 files changed, 11 insertions(+), 39 deletions(-)
>>>
>>> diff --git a/drivers/net/sfc/sfc_ethdev.c b/drivers/net/sfc/sfc_ethdev.c
>>> index 2f5f86f84877..e0a12b32b1a3 100644
>>> --- a/drivers/net/sfc/sfc_ethdev.c
>>> +++ b/drivers/net/sfc/sfc_ethdev.c
>>> @@ -238,22 +238,12 @@ static int
>>>    sfc_dev_link_update(struct rte_eth_dev *dev, int wait_to_complete)
>>>    {
>>>    	struct sfc_adapter *sa = dev->data->dev_private;
>>> -	struct rte_eth_link *dev_link = &dev->data->dev_link;
>>> -	struct rte_eth_link old_link;
>>>    	struct rte_eth_link current_link;
>>>    
>>>    	sfc_log_init(sa, "entry");
>>>    
>>> -retry:
>>> -	EFX_STATIC_ASSERT(sizeof(*dev_link) == sizeof(rte_atomic64_t));
>>> -	*(int64_t *)&old_link = rte_atomic64_read((rte_atomic64_t *)dev_link);
>>> -
>>>    	if (sa->state != SFC_ADAPTER_STARTED) {
>>>    		sfc_port_link_mode_to_info(EFX_LINK_UNKNOWN, &current_link);
>>> -		if (!rte_atomic64_cmpset((volatile uint64_t *)dev_link,
>>> -					 *(uint64_t *)&old_link,
>>> -					 *(uint64_t *)&current_link))
>>> -			goto retry;
>>>    	} else if (wait_to_complete) {
>>>    		efx_link_mode_t link_mode;
>>>    
>>> @@ -261,21 +251,18 @@ sfc_dev_link_update(struct rte_eth_dev *dev, int wait_to_complete)
>>>    			link_mode = EFX_LINK_UNKNOWN;
>>>    		sfc_port_link_mode_to_info(link_mode, &current_link);
>>>    
>>> -		if (!rte_atomic64_cmpset((volatile uint64_t *)dev_link,
>>> -					 *(uint64_t *)&old_link,
>>> -					 *(uint64_t *)&current_link))
>>> -			goto retry;
>>>    	} else {
>>>    		sfc_ev_mgmt_qpoll(sa);
>>> -		*(int64_t *)&current_link =
>>> -			rte_atomic64_read((rte_atomic64_t *)dev_link);
>>> +		_rte_eth_linkstatus_get(dev, &current_link);
>>>    	}
>>>    
>>> -	if (old_link.link_status != current_link.link_status)
>>> -		sfc_info(sa, "Link status is %s",
>>> -			 current_link.link_status ? "UP" : "DOWN");
>>> +	if (_rte_eth_linkstatus_set(dev, &current_link) == 0)
>>> +		return 0;
>>> +
>>> +	sfc_info(sa, "Link status is %s",
>>> +		 current_link.link_status ? "UP" : "DOWN");
>>>    
>>> -	return old_link.link_status == current_link.link_status ? 0 : -1;
>>> +	return -1;
>>>    }
>>>    
>>>    static void
>>> diff --git a/drivers/net/sfc/sfc_ev.c b/drivers/net/sfc/sfc_ev.c
>>> index a16dc27b380e..3e96536a9d60 100644
>>> --- a/drivers/net/sfc/sfc_ev.c
>>> +++ b/drivers/net/sfc/sfc_ev.c
>>> @@ -404,29 +404,14 @@ sfc_ev_link_change(void *arg, efx_link_mode_t link_mode)
>>>    {
>>>    	struct sfc_evq *evq = arg;
>>>    	struct sfc_adapter *sa = evq->sa;
>>> -	struct rte_eth_link *dev_link = &sa->eth_dev->data->dev_link;
>>>    	struct rte_eth_link new_link;
>>> -	uint64_t new_link_u64;
>>> -	uint64_t old_link_u64;
>>> -
>>> -	EFX_STATIC_ASSERT(sizeof(*dev_link) == sizeof(rte_atomic64_t));
>>>    
>>>    	sfc_port_link_mode_to_info(link_mode, &new_link);
>>> +	if (_rte_eth_linkstatus_set(sa->eth_dev, &new_link) == 0)
>>> +		return B_FALSE;
>>>    
>>> -	new_link_u64 = *(uint64_t *)&new_link;
>>> -	do {
>>> -		old_link_u64 = rte_atomic64_read((rte_atomic64_t *)dev_link);
>>> -		if (old_link_u64 == new_link_u64)
>>> -			break;
>>> -
>>> -		if (rte_atomic64_cmpset((volatile uint64_t *)dev_link,
>>> -					old_link_u64, new_link_u64)) {
>>> -			evq->sa->port.lsc_seq++;
>>> -			break;
>>> -		}
>>> -	} while (B_TRUE);
>>> -
>>> -	return B_FALSE;
>>> +	evq->sa->port.lsc_seq++;
>>> +	return B_TRUE;
>> It still returns B_TRUE, but should return B_FALSE as before.
>> Also before the patch lsc_seq is incremented in the case of any
>> changes in link status, but now in the case of up/down change only.
> The old code looked broken and did not match the comments.
> It always returned B_FALSE independent of whether link status changed
> or not.

Which comments does it not match?
Yes, because it is internal callback and return value is unrelated to link
status changes. Return value affects further events processing.
If B_TRUE is returned, it means something bad has happened and
events processing should be aborted.