netdev - Re: [PATCH net-next v2 1/7] mld: convert from timer to delayed work

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Date:   Mon, 15 Feb 2021 10:04:18 -0800
From:   Cong Wang <xiyou.wangcong@...il.com>
To:     Taehee Yoo <ap420073@...il.com>
Cc:     David Miller <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Linux Kernel Network Developers <netdev@...r.kernel.org>,
        jwi@...ux.ibm.com, kgraul@...ux.ibm.com, hca@...ux.ibm.com,
        gor@...ux.ibm.com, borntraeger@...ibm.com,
        Marek Lindner <mareklindner@...mailbox.ch>,
        sw@...onwunderlich.de, a@...table.cc, sven@...fation.org,
        Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>, dsahern@...nel.org
Subject: Re: [PATCH net-next v2 1/7] mld: convert from timer to delayed work

On Sun, Feb 14, 2021 at 2:56 AM Taehee Yoo <ap420073@...il.com> wrote:
>
>
>
> On 21. 2. 14. 오전 4:07, Cong Wang wrote:
>  > On Sat, Feb 13, 2021 at 9:51 AM Taehee Yoo <ap420073@...il.com> wrote:
>  >> -static void mld_dad_start_timer(struct inet6_dev *idev, unsigned
> long delay)
>  >> +static void mld_dad_start_work(struct inet6_dev *idev, unsigned
> long delay)
>  >>   {
>  >>          unsigned long tv = prandom_u32() % delay;
>  >>
>  >> -       if (!mod_timer(&idev->mc_dad_timer, jiffies+tv+2))
>  >> +       if (!mod_delayed_work(mld_wq, &idev->mc_dad_work,
> msecs_to_jiffies(tv + 2)))
>  >
>  > IIUC, before this patch 'delay' is in jiffies, after this patch it is
> in msecs?
>  >
>
> Ah, I understand, It's my mistake.
> I didn't change the behavior of 'delay' in this patchset.
> So, 'delay' is still in jiffies, not msecs.
> Therefore, msecs_to_jiffies() should not be used in this patchset.
> I will send a v3 patch, which doesn't use msecs_to_jiffies().
> Thanks!
>
> By the way, I think the 'delay' is from the
> unsolicited_report_interval() and it just return value of
> idev->cnf.mldv{1 | 2}_unsolicited_report_interval.
> I think this value is msecs, not jiffies.
> So, It should be converted to use msecs_to_jiffies(), I think.
> How do you think about it?

Hmm? I think it is in jiffies:

        .mldv1_unsolicited_report_interval = 10 * HZ,
        .mldv2_unsolicited_report_interval = HZ,


>
>  > [...]
>  >
>  >> -static void mld_dad_timer_expire(struct timer_list *t)
>  >> +static void mld_dad_work(struct work_struct *work)
>  >>   {
>  >> -       struct inet6_dev *idev = from_timer(idev, t, mc_dad_timer);
>  >> +       struct inet6_dev *idev = container_of(to_delayed_work(work),
>  >> +                                             struct inet6_dev,
>  >> +                                             mc_dad_work);
>  >>
>  >> +       rtnl_lock();
>  >
>  > Any reason why we need RTNL after converting the timer to
>  > delayed work?
>  >
>
> For the moment, RTNL is not needed.
> But the Resources, which are used by delayed_work will be protected by
> RTNL instead of other locks.
> So, It just pre-adds RTNL and the following patches will delete other locks.

Sounds like this change does not belong to this patch. ;) If so,
please move it to where ever more appropriate.

Thanks.