From: Matan Azrad <matan@nvidia.com>
To: Maxime Coquelin <maxime.coquelin@redhat.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 20:13:02 +0000 [thread overview]
Message-ID: <MW2PR12MB2492DD30C6D00BC0C44DD5F7DFA19@MW2PR12MB2492.namprd12.prod.outlook.com> (raw)
In-Reply-To: <c574b1ba-10d5-3fa6-c3bb-5300758114ae@redhat.com>
From: Maxime Coquelin
> 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.
We have system calls there per queue.
No need this optional delay just because of mutex cleaning.
> 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
> >>>>>
> >>>
> >
next prev parent reply other threads:[~2021-01-21 20:13 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
2021-01-21 20:13 ` Matan Azrad [this message]
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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