[dpdk-dev] [PATCH 04/22] ethdev: enable hotplug on multi-process

[Burakov, Anatoly]

On 19-Jun-18 4:22 AM, Zhang, Qi Z wrote:
> 
> 
>> -----Original Message-----
>> From: Burakov, Anatoly
>> Sent: Monday, June 18, 2018 4:18 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 04/22] ethdev: enable hotplug on multi-process
>>
>> On 07-Jun-18 1:38 PM, Qi Zhang wrote:
>>> The patch introduce the solution to handle different hotplug cases in
>>> multi-process situation, it include below scenario:
>>>
>>> 1. Attach a share device from primary
>>> 2. Detach a share device from primary
>>> 3. Attach a share device from secondary 4. Detach a share device from
>>> secondary 5. Attach a private device from secondary 6. Detach a
>>> private device from secondary 7. Detach a share device from secondary
>>> privately 8. Attach a share device from secondary privately
>>>
>>> In primary-secondary process model, we assume device is shared by
>> default.
>>> that means attach or detach a device on any process will broadcast to
>>> all other processes through mp channel then device information will be
>>> synchronized on all processes.
>>>
>>> Any failure during attaching process will cause inconsistent status
>>> between processes, so proper rollback action should be considered.
>>> Also it is not safe to detach a share device when other process still
>>> use it, so a handshake mechanism is introduced, it will be implemented
>>> in following separate patch.
>>>
>>> Scenario for Case 1, 2:
>>>
>>> attach device
>>> a) primary attach the new device if failed goto h).
>>> b) primary send attach sync request to all secondary.
>>> c) secondary receive request and attach device and send reply.
>>> d) primary check the reply if all success go to i).
>>> e) primary send attach rollback sync request to all secondary.
>>> f) secondary receive the request and detach device and send reply.
>>> g) primary receive the reply and detach device as rollback action.
>>> h) attach fail
>>> i) attach success
>>>
>>> detach device
>>> a) primary perform pre-detach check, if device is locked, goto i).
>>> b) primary send pre-detach sync request to all secondary.
>>> c) secondary perform pre-detach check and send reply.
>>> d) primary check the reply if any fail goto i).
>>> e) primary send detach sync request to all secondary
>>> f) secondary detach the device and send reply (assume no fail)
>>> g) primary detach the device.
>>> h) detach success
>>> i) detach failed
>>>
>>> Case 3, 4:
>>> This will be implemented in following patch.
>>
>> If these will be implemented in following patch, why spend half the commit
>> message talking about it? :)
> 
> Sorry, I didn't get your point about "see half commit to talk about it" :)
> This patch covered an overview, and also the implementation of case 1,2,5,6,7,8
> 
> For case 3, 4, just below 4 lines to describe it
> 
> 3. Attach a share device from secondary.
> 4. Detach a share device from secondary.
> Case 3, 4:
> This will be implemented in following patch.
> 
>> is commit doesn't implement secondary
>> process functionality at all, so the commit message should probably be
>> reworded to only include primary process logic, no?
> 
> OK, I will reword it to highlight the patch's scope as description at above.

Thanks!

<snip>

> 
> The return value of rte_eth_dev_request_to_primary only means communication fail,
> (message not able to send, or not get reply in time).
> but not the fail on attach/detach itself. (which comes from req->result)
> 

Ah, yes, my apologies, you're right! The log message is fine then.

<snip>

>>
>> Do we have to do a similar check for failsafe devices?
> 
> Just keep it same logic as before, it could be a separate patch to fix I guess.

Sure.

<snip>

>> Here and in other places: rte_strlcpy?
> 
> OK

Apologies, this should read strlcpy, not rte_strlcpy.

-- 
Thanks,
Anatoly