Re: [dpdk-stable] [PATCH] vdpa/mlx5: fix configuration mutex cleanup

[Maxime Coquelin <maxime.coquelin@redhat.com>]

On 1/14/21 2:09 PM, Matan Azrad wrote:
> 
> 
> From: Maxime Coquelin
>> Hi Matan,
>>
>> On 1/14/21 12:49 PM, Matan Azrad wrote:
>>> Hi Maxime and David
>>>
>>> Thank you for Review.
>>>
>>> From: David Marchand
>>>> On Fri, Jan 8, 2021 at 9:48 AM David Marchand
>>>> <david.marchand@redhat.com> wrote:
>>>>>> I wonder if it would be possible and cleaner to disable
>>>>>> cancellation on the thread while the mutex is held?
>>>
>>> Yes, we can cause thread to return by some global variable sync.
>>> It is the same logic.
>>
>> No, that was not my suggestion. My suggestion is to block the thread
>> cancellation while in the critical section, using pthread_setcancelstate().
> 
> Yes, Generally it is better to let the thread control his cancellation, either cancel itself or enabling\disabling cancellations. 
> 
> I don't see a reason to wait for the thread in current logic - the critical section is not important to be completed here.

The reason I see is there are quite a few things done in this critical
section. And if tomorrow someone add new things in it, he may not know
the thread can be cancelled at any time, which could cause hard to debug
issues.

> We just want to close the thread and to clean the mutex. 
>  
>>>>> +1
>>>>
>>>> IEEE Std 1003.1-2001/Cor 2-2004, item XBD/TC2/D6/26 is applied,
>>>> adding pthread_t to the list of types that are not required to be
>>>> arithmetic types, thus allowing pthread_t to be defined as a structure.
>>>>
>>>> It would be better to leave pthread_t alone and not interpret it:
>>>>
>>>> if (priv->timer_tid) {
>>>>     pthread_cancel(priv->timer_tid);
>>>>     pthread_join(priv->timer_tid, &status); }
>>>> priv->timer_tid = 0;
>>>
>>>
>>> I'm not sure why you think it is better in this specific case.
>>> The cancellation will close the thread in faster way, no need to wait for the
>> thread to close itself.
>>>
>>>
>>>>
>>>> --
>>>> David Marchand
>>>
>