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From:   Krishna Chaitanya <chaitanya.mgit@gmail.com>
Date:   Thu, 20 Aug 2020 23:12:29 +0530
Message-ID: <CABPxzYLOZf9Fu5O3Rt_mVcXeFLuuFAsqyvd7jiCVvJ0x2BN-+g@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 11:11 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?