[dpdk-dev] [PATCH v2 06/22] ethdev: support attach or detach share device from secondary

[Burakov, Anatoly]

On 21-Jun-18 1:50 PM, Zhang, Qi Z wrote:
> 
> 
>> -----Original Message-----
>> From: Burakov, Anatoly
>> Sent: Thursday, June 21, 2018 5:06 PM
>> To: Zhang, Qi Z <qi.z.zhang at intel.com>; thomas at monjalon.net
>> Cc: Ananyev, Konstantin <konstantin.ananyev at intel.com>; dev at dpdk.org;
>> Richardson, Bruce <bruce.richardson at intel.com>; Yigit, Ferruh
>> <ferruh.yigit at intel.com>; Shelton, Benjamin H
>> <benjamin.h.shelton at intel.com>; Vangati, Narender
>> <narender.vangati at intel.com>
>> Subject: Re: [PATCH v2 06/22] ethdev: support attach or detach share device
>> from secondary
>>
>> On 21-Jun-18 3:00 AM, Qi Zhang wrote:
>>> This patch cover the multi-process hotplug case when a share device
>>> attach/detach request be issued from secondary process, the
>>> implementation references malloc_mp.c.
>>>
>>> device attach on secondary:
>>> a) secondary send async request to primary and wait on a condition
>>>      which will be released by matched response from primary.
>>> b) primary receive the request and attach the new device if failed
>>>      goto i).
>>> c) primary forward attach request to all secondary as async request
>>>      (because this in mp thread context, use sync request will
>>> deadlock)
>>> d) secondary receive request and attach device and send reply.
>>> e) primary check the reply if all success go to j).
>>> f) primary send attach rollback async request to all secondary.
>>> g) secondary receive the request and detach device and send reply.
>>> h) primary receive the reply and detach device as rollback action.
>>> i) send fail response to secondary, goto k).
>>> j) send success response to secondary.
>>> k) secondary process receive response and return.
>>>
>>> device detach on secondary:
>>> a) secondary send async request to primary and wait on a condition
>>>      which will be released by matched response from primary.
>>> b) primary receive the request and  perform pre-detach check, if device
>>>      is locked, goto j).
>>> c) primary send pre-detach async request to all secondary.
>>> d) secondary perform pre-detach check and send reply.
>>> e) primary check the reply if any fail goto j).
>>> f) primary send detach async request to all secondary
>>> g) secondary detach the device and send reply
>>> h) primary detach the device.
>>> i) send success response to secondary, goto k).
>>> j) send fail response to secondary.
>>> k) secondary process receive response and return.
>>>
>>> Signed-off-by: Qi Zhang <qi.z.zhang at intel.com>
>>> ---
>>>
>>
>> <snip>
>>
>>> -static int handle_secondary_request(const struct rte_mp_msg *msg,
>>> const void *peer)
>>> +static int
>>> +check_reply(const struct eth_dev_mp_req *req, const struct
>>> +rte_mp_reply *reply) {
>>> +	struct eth_dev_mp_req *resp;
>>> +	int i;
>>> +
>>> +	if (reply->nb_received != reply->nb_sent)
>>> +		return -EINVAL;
>>> +
>>> +	for (i = 0; i < reply->nb_received; i++) {
>>> +		resp = (struct eth_dev_mp_req *)reply->msgs[i].param;
>>> +
>>> +		if (resp->t != req->t) {
>>> +			ethdev_log(ERR, "Unexpected response to async request\n");
>>> +			return -EINVAL;
>>> +		}
>>> +
>>> +		if (resp->id != req->id) {
>>> +			ethdev_log(ERR, "response to wrong async request\n");
>>> +			return -EINVAL;
>>> +		}
>>> +
>>> +		if (resp->result)
>>> +			return resp->result;
>>> +	}
>>> +
>>> +	return 0;
>>> +}
>>
>> As far as i understand, return values from this will propagate all the way up to
>> user return value.
> Yes
>> How would a user differentiate between -EINVAL returned
>> from invalid parameters, and -EINVAL from failed reply?
> 
> My understanding is if
>   (resp->t != req->t) or (resp->id != req->id) is not expected to happen at any condition.
> there should be a bug if it does happen.
> So the return value is not necessary to be sensitive.
> Am I right?

You're right, it won't happen under normal conditions. However, on the 
off-chance that it does, the error return should still be meaningful. 
Under normal conditions, malloc() doesn't fail either :)

-- 
Thanks,
Anatoly