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Subject: Re: [RFC] ath10k: change to do napi_enable and napi_disable when
 insmod and rmmod for sdio
To:     Krishna Chaitanya <chaitanya.mgit@gmail.com>,
        Wen Gong <wgong@codeaurora.org>
Cc:     Kalle Valo <kvalo@codeaurora.org>,
        linux-wireless <linux-wireless@vger.kernel.org>,
        ath10k <ath10k@lists.infradead.org>
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From:   Ben Greear <greearb@candelatech.com>
Organization: Candela Technologies
Message-ID: <acb2bd58-2f95-e09c-9575-b45c0e2aeb70@candelatech.com>
Date:   Thu, 20 Aug 2020 09:32:52 -0700
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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.

Thanks,
Ben


-- 
Ben Greear <greearb@candelatech.com>
Candela Technologies Inc  http://www.candelatech.com