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From:   Krishna Chaitanya <chaitanya.mgit@gmail.com>
Date:   Fri, 21 Aug 2020 01:45:49 +0530
Message-ID: <CABPxzY+uyy_Yc0mHb7sJGxxUE5__Z8SpywodAv2YCM8D89waHw@mail.gmail.com>
Subject: Re: [RFC] ath10k: change to do napi_enable and napi_disable when
 insmod and rmmod for sdio
To:     Ben Greear <greearb@candelatech.com>
Cc:     Wen Gong <wgong@codeaurora.org>, Kalle Valo <kvalo@codeaurora.org>,
        linux-wireless <linux-wireless@vger.kernel.org>,
        ath10k <ath10k@lists.infradead.org>
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On Thu, Aug 20, 2020 at 11:23 PM Ben Greear <greearb@candelatech.com> wrote:
>
> On 8/20/20 10:42 AM, Krishna Chaitanya wrote:
> > On Thu, Aug 20, 2020 at 11:11 PM Krishna Chaitanya
> > <chaitanya.mgit@gmail.com> wrote:
> >>
> >> On Thu, Aug 20, 2020 at 10:38 PM Ben Greear <greearb@candelatech.com> wrote:
> >>>
> >>> On 8/20/20 10:00 AM, Krishna Chaitanya wrote:
> >>>> On Thu, Aug 20, 2020 at 10:02 PM Ben Greear <greearb@candelatech.com> wrote:
> >>>>>
> >>>>> On 8/20/20 9:08 AM, Krishna Chaitanya wrote:
> >>>>>> On Thu, Aug 20, 2020 at 8:07 PM Wen Gong <wgong@codeaurora.org> wrote:
> >>>>>>>
> >>>>>>> On 2020-08-20 18:52, Krishna Chaitanya wrote:
> >>>>>>>> On Thu, Aug 20, 2020 at 3:45 PM Wen Gong <wgong@codeaurora.org> wrote:
> >>>>>>>>>
> >>>>>>>>> On 2020-08-20 17:19, Krishna Chaitanya wrote:
> >>>>>>> ...
> >>>>>>>>>>> I'm not really convinced that this is the right fix, but I'm no NAPI
> >>>>>>>>>>> expert. Can anyone else help?
> >>>>>>>>>> Calling napi_disable() twice can lead to hangs, but moving NAPI from
> >>>>>>>>>> start/stop to
> >>>>>>>>>> the probe isn't the right approach as the datapath is tied to
> >>>>>>>>>> start/stop.
> >>>>>>>>>>
> >>>>>>>>>> Maybe check the state of NAPI before disable?
> >>>>>>>>>>
> >>>>>>>>>>     if (test_bit(NAPI_STATE_SCHED, &ar->napi.napi.state))
> >>>>>>>>>>      napi_disable(&ar->napi)
> >>>>>>>>>> or maintain napi_state like this
> >>>>>>>>>> https://patchwork.kernel.org/patch/10249365/
> >>>>>>>>> it is better to use above link's patch.
> >>>>>>>>> napi.state is controlled by napi API, it is better ath10k not know it.
> >>>>>>>> Sure, but IMHO just canceling the async rx work should solve the issue.
> >>>>>>> Oh no, canceling the async rx work will not solve this issue, rx worker
> >>>>>>> ath10k_rx_indication_async_work call napi_schedule, after napi_complete,
> >>>>>>> the NAPI_STATE_SCHED will clear.
> >>>>>>> The issue of this patch is because 2 thread called to hif_stop and
> >>>>>>> NAPI_STATE_SCHED not clear.
> >>>>>> That fix is still valid and good to have.
> >>>>>>
> >>>>>> ndev_stop being called twice is typical scenarios (stop vs rmmod), so
> >>>>>>     just checking the netdev_flags for IFF_UP and returning from hif_Stop
> >>>>>> should suffice, no?
> >>>>>
> >>>>> My approach to fix this problem was to add a boolean in ath10k as to whether
> >>>>> it had napi enabled or not, and then check that before trying to enable/disable
> >>>>> it again.  Seems to work fine, and cleaner in my mind than checking internal
> >>>>> napi flags.
> >>>> A much simpler approach is just to check for IFF_UP and skip NAPI (and others)
> >>>> in the hif_stop no? (provided proper RTNL locking is done if hif_stop
> >>>> is being called
> >>>> internally as well).
> >>>>
> >>>
> >>> I'm not sure, but I think the driver should be internally consistent and not
> >>> spend a lot of time trying to guess about interactions with objects higher
> >>> in the stack.
> >> Fair enough, the network interface state is a basic thing controlled
> >> by the driver,
> >> so, should be okay to use. Anyways, the in-driver approach has more control.
> >>>
> >>> Here is my original patch to fix this, it is not complex.
> >>>
> >>> https://patchwork.kernel.org/patch/10249363/
> >> Sure, I have shared your patch above :).
> > Sent a bit early, any idea why this wasn't upstreamed earlier?
>
> No, one comment from Michal indicated maybe there were more problems lurking
> in this area, but he seemed to be OK with the patch over all.  After that,
> it was just ignored.
>
Now might be a good time to push for it :)