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

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Message-ID: <ZOof7EE0tXAt0YN7@hovoldconsulting.com>
Date:   Sat, 26 Aug 2023 17:53:16 +0200
From:   Johan Hovold <johan@...nel.org>
To:     Kalle Valo <kvalo@...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""

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/

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.

Johan