linux-kernel - Re: [PATCH v2 0/3] serial: qcom-geni: fix lockups

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Message-ID: <CAD=FV=X0Sk0Xkz7Mcna6BNhGpxZQY5KArY=LqMPEwbocvmojQA@mail.gmail.com>
Date: Mon, 8 Jul 2024 16:57:55 -0700
From: Doug Anderson <dianders@...omium.org>
To: Greg Kroah-Hartman <gregkh@...uxfoundation.org>, Johan Hovold <johan+linaro@...nel.org>
Cc: Jiri Slaby <jirislaby@...nel.org>, Konrad Dybcio <konrad.dybcio@...aro.org>, 
	Bjorn Andersson <andersson@...nel.org>, linux-arm-msm@...r.kernel.org, 
	linux-serial@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 0/3] serial: qcom-geni: fix lockups

Johan,

On Thu, Jul 4, 2024 at 3:31 AM Greg Kroah-Hartman
<gregkh@...uxfoundation.org> wrote:
>
> On Thu, Jul 04, 2024 at 12:18:02PM +0200, Johan Hovold wrote:
> > Since 6.10-rc1, Qualcomm machines with a serial port can easily lock up
> > hard, for example, when stopping a getty on reboot.
> >
> > This was triggered by the kfifo conversion, which turned an existing bug
> > that caused the driver to print discarded characters after a buffer
> > flush into a hard lockup.
> >
> > This series fixes the regression and a related soft lockup issue that
> > can be triggered on software flow control and on suspend.
> >
> > Doug has posted an alternative series of fixes here that depends on
> > reworking the driver a fair bit here:
> >
> >       https://lore.kernel.org/lkml/20240610222515.3023730-1-dianders@chromium.org/
> >
> > This rework has a significant impact on performance on some platforms,
> > but fortunately it seems such a rework can be avoided.
> >
> > There are further bugs in the console code (e.g. that can lead to lost
> > characters) that this series does not address, but those can be fixed
> > separately (and I've started working on that).
>
> I'll take these now, thanks!

Are you going to continue to work on the driver? There are still some
pretty bad bugs including ones that are affecting Collabora's test
labs. Unless you want to try to tackle it some other way, I'm going to
keep pushing for something like my original series to land. I can
re-post them atop your patches since they've landed. This will regress
your performance but correctness trumps performance.

-Doug