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From: Maxime Coquelin <maxime.coquelin@redhat.com>
To: Matan Azrad <matan@nvidia.com>,
	David Marchand <david.marchand@redhat.com>
Cc: dev <dev@dpdk.org>, dpdk stable <stable@dpdk.org>
Subject: Re: [dpdk-dev] [dpdk-stable] [PATCH] vdpa/mlx5: fix configuration mutex cleanup
Date: Thu, 21 Jan 2021 11:46:07 +0100
Message-ID: <c574b1ba-10d5-3fa6-c3bb-5300758114ae@redhat.com> (raw)
In-Reply-To: <MW2PR12MB249203CB1495DD64F04A2689DFA80@MW2PR12MB2492.namprd12.prod.outlook.com>



On 1/14/21 4:23 PM, Matan Azrad wrote:
> 
> 
> From: Maxime Coquelin
>> 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.
> 
> As I said, here it is not needed, this thread designed just to cause guest notifications.
> 
> The optional future developer mistake can be done also outside the critical section in in any other place - we cannot protect it.
> 
> The design choice is to close the thread fast.

But why is it so urgent that it cannot been stopped cleanly?
I don't think it would add seconds delay by doing it in a clean way.

Thanks,
Maxime

>>> 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
>>>>>
>>>
> 


  reply	other threads:[~2021-01-21 10:46 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-01-06  6:43 [dpdk-dev] " Matan Azrad
2021-01-07 18:09 ` Maxime Coquelin
2021-01-08  8:48   ` [dpdk-dev] [dpdk-stable] " David Marchand
2021-01-14  8:34     ` David Marchand
2021-01-14 11:49       ` Matan Azrad
2021-01-14 12:38         ` Maxime Coquelin
2021-01-14 13:09           ` Matan Azrad
2021-01-14 14:27             ` Maxime Coquelin
2021-01-14 15:23               ` Matan Azrad
2021-01-21 10:46                 ` Maxime Coquelin [this message]
2021-01-21 20:13                   ` Matan Azrad
2021-01-26 10:22                     ` Maxime Coquelin
2021-01-26 10:45                       ` Matan Azrad
2021-01-26 13:00                         ` Maxime Coquelin
2021-01-26 18:23                           ` Matan Azrad
2021-01-27 10:45 ` [dpdk-dev] " Maxime Coquelin
2021-01-27 12:01 ` Maxime Coquelin

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