Re: [dpdk-dev] [PATCH v2] ixgbe: Fix disable interrupt twice

["Qiu, Michael" <michael.qiu@intel.com>]

On 2016/2/2 19:03, Ananyev, Konstantin wrote:
>

[...]

>>>> I don't think i40e miss it, because it not the right please to disable interrupt.
>>>> because all interrupts are enabled in init stage.
>>>>
>>>> Actually, ixgbe enable the interrupt in init stage, but in dev_start, it disable it
>>>> first and re-enable, so it just the same with doing nothing about interrupt.
>>>>
>>>> Just think below:
>>>>
>>>> 1. start the port.(interrupt already enabled in init stage, disable -->
>>>> re-enable)
>>>> 2. stop the port.(disable interrupt)
>>>> 3. start port again(Try to disable, but failed, already disabled)
>>>>
>>>> Would you think the code has issue?
>>> [Zhang, Helin] in ixgbe PMD, it can be seen that uninit() calls dev_close(),
>>> which calls dev_stop(). So I think the disabling can be done only in dev_stop().
>>> All others can make use of dev_stop to disable the interrupt.
>> As I said, if it is in dev_stop, it will has issue when dev_start -->
>> dev_stop --> dev_start, this also could applied in i40e and fm10k. If
>> you want to put it in dev_stop, better to remove enable interrupts in
>> init stage, and only put it in dev_start.
> We can't remove enabling interrupt at init stage and put it only in dev_start().
> That means PF couldn't handle interrupts from VF till dev_start() will be executed on PF
>  - which could never happen.
> For same reason we can't disable all interrupts in dev_stop().
> See: http://dpdk.org/ml/archives/dev/2015-November/027238.html

Hi, Konstantin

Yes, you are right.

So the only way to fix this issue should remove it in dev_stop(), and
left it in uinit() stage, which my patch does.

Am I right?

Thanks,
Michael
> Konstantin
>
>> Thanks,
>> Michael
>>> Regards,
>>> Helin
>>>
>>>> Thanks,
>>>> Michael
>>>>
>>>>> Maybe we can follow fm10k's style.
>>>>>
>>>>>> On other hand, if we remove it in dev_stop, any side effect? In ixgbe
>>>>>> start, it will always disable it first and then re-enable it, so it's safe.
>>>>> I think you mean we can disable intr anyway even if it has been disabled.
>>>> Actually, we couldn't, DPDK call VFIO ioctl to kernel to disable interrupts, and
>>>> if we try disable twice, it will return and error.
>>>> That's why I mean we need a flag to show the interrupts stats. If it already
>>>> disabled, we do not need call in to kernel. just return and give a warning
>>>> message.
>>>>
>>>> Thanks,
>>>> Michael
>>>>
>>>>>  Sounds more like why we don't
>>>>> need this patch :)
>>>>>
>>>>>> Thanks,
>>>>>> Michael
>