linux-kernel - Re: [PATCH] Revert "Revert "wifi: ath11k: Enable threaded NAPI""

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Message-ID: <87leduf4ts.fsf@kernel.org>
Date:   Tue, 29 Aug 2023 14:47:27 +0300
From:   Kalle Valo <kvalo@...nel.org>
To:     Johan Hovold <johan@...nel.org>
Cc:     Jeff Johnson <quic_jjohnson@...cinc.com>,
        Bjorn Andersson <quic_bjorande@...cinc.com>,
        Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>,
        Konrad Dybcio <konrad.dybcio@...aro.org>,
        Manikanta Pubbisetty <quic_mpubbise@...cinc.com>,
        ath11k@...ts.infradead.org, linux-wireless@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Revert "Revert "wifi: ath11k: Enable threaded NAPI""

Johan Hovold <johan@...nel.org> writes:

> On Tue, Aug 22, 2023 at 03:44:45PM +0200, Johan Hovold wrote:
>> On Tue, Aug 22, 2023 at 03:56:24PM +0300, Kalle Valo wrote:
>> > Johan Hovold <johan@...nel.org> writes:
>> > > On Wed, Aug 09, 2023 at 09:34:32AM +0200, Johan Hovold wrote:
>> > >
>> > >> Disabling threaded NAPI caused a severe regression in 6.5-rc5 by making
>> > >> the X13s completely unusable (e.g. no keyboard input, I've seen an RCU
>> > >> splat once).
>> 
>> > > Any chance we can get the offending commit reverted before 6.5 is
>> > > released? 
>> > 
>> > The problem here is that would break QCN9074 again so there is no good
>> > solution. I suspect we have a fundamental issue in ath11k which we just
>> > haven't discovered yet. I would prefer to get to the bottom of this
>> > before reverting anything.
>> 
>> Sure, ideally we can find and fix the underlying issues these next few
>> days, but since this regression was introduced in rc5 in an attempt to
>> address the QCN9074 issue which has been there since 6.1 I think we
>> need to revert otherwise. 
>
> I've managed to track down what causes the hang on the X13s after
> disabling threaded NAPI. Turns out to be a severe regression in the
> genirq code that causes the software resend tasklet to loop
> indefinitely.
>
> I've just sent a fix here:
>
> 	https://lore.kernel.org/lkml/20230826154004.1417-1-johan+linaro@kernel.org/

Oh wow, that's a tricky bug :o I'm sure it was not easy to find.

> I've also made some progress on the QCN9074 hang, but keeping the
> threaded NAPI revert for now is indeed the right thing to do.

Ok, thanks for the update and looking at also this problem. Very much
appreciated! I'm sure we have a major bug lurking somewhere in ath11k,
would be so good to fix that.

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