[RFC] ath10k: change to do napi_enable and napi_disable when insmod and rmmod for sdio

[Krishna Chaitanya]

On Thu, Aug 20, 2020 at 10:02 PM Ben Greear <greearb at 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 at codeaurora.org> wrote:
> >>
> >> On 2020-08-20 18:52, Krishna Chaitanya wrote:
> >>> On Thu, Aug 20, 2020 at 3:45 PM Wen Gong <wgong at 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).