Re: [dpdk-dev] [PATCH v2] kni: Fix request overwritten

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

On 10/4/2021 2:09 PM, Elad Nachman wrote:
> Hi,
> 
> EAGAIN is propogated back to the kernel and to the caller.
> 

So will the user get an error, or it will be handled by the kernel and retried?

> We cannot retry from the kni kernel module since we hold the rtnl lock.
> 

Why not? We are already waiting until a command time out, like 'kni_net_open()'
can retry if 'kni_net_process_request()' returns '-EAGAIN'. And we can limit the
number of retry for safety.

> FYI,
> 
> Elad
> 
> בתאריך יום ב׳, 4 באוק׳ 2021, 16:05, מאת Ferruh Yigit ‏<
> ferruh.yigit@intel.com>:
> 
>> On 9/24/2021 11:54 AM, Elad Nachman wrote:
>>> Fix lack of multiple KNI requests handling support by introducing a
>>> request in progress flag which will fail additional requests with
>>> EAGAIN return code if the original request has not been processed
>>> by user-space.
>>>
>>> Bugzilla ID: 809
>>
>> Hi Eric,
>>
>> Can you please test this patch, if it solves the issue you reported?
>>
>>>
>>> Signed-off-by: Elad Nachman <eladv6@gmail.com>
>>> ---
>>>  kernel/linux/kni/kni_net.c | 9 +++++++++
>>>  lib/kni/rte_kni.c          | 2 ++
>>>  lib/kni/rte_kni_common.h   | 1 +
>>>  3 files changed, 12 insertions(+)
>>>
>>
>> <...>
>>
>>> @@ -123,7 +124,15 @@ kni_net_process_request(struct net_device *dev,
>> struct rte_kni_request *req)
>>>
>>>       mutex_lock(&kni->sync_lock);
>>>
>>> +     /* Check that existing request has been processed: */
>>> +     cur_req = (struct rte_kni_request *)kni->sync_kva;
>>> +     if (cur_req->req_in_progress) {
>>> +             ret = -EAGAIN;
>>
>> Overall logic in the KNI looks good to me, this helps to serialize the
>> requests
>> even for async ones.
>>
>> But can you please clarify how it behaves in the kernel side with '-EAGAIN'
>> return type? Will linux call the ndo again, or will it just fail.
>>
>> If it just fails should we handle the re-try on '-EAGAIN' within the kni
>> module?
>>
>>