linux-kernel - Re: [PATCH 0/4] serial: qcom-geni: fix console shutdown hang

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Message-ID: <ZAduTSTirQbqZlIg@hovoldconsulting.com>
Date:   Tue, 7 Mar 2023 18:03:09 +0100
From:   Johan Hovold <johan@...nel.org>
To:     Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
Cc:     Johan Hovold <johan+linaro@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Andy Gross <agross@...nel.org>,
        Konrad Dybcio <konrad.dybcio@...aro.org>,
        Jiri Slaby <jirislaby@...nel.org>,
        Douglas Anderson <dianders@...omium.org>,
        Daniel Thompson <daniel.thompson@...aro.org>,
        linux-arm-msm@...r.kernel.org, linux-serial@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
Subject: Re: [PATCH 0/4] serial: qcom-geni: fix console shutdown hang

On Tue, Mar 07, 2023 at 05:47:27PM +0100, Bartosz Golaszewski wrote:
> On Tue, 7 Mar 2023 at 17:44, Bartosz Golaszewski
> <bartosz.golaszewski@...aro.org> wrote:
> >
> > On Tue, 7 Mar 2023 at 17:43, Johan Hovold <johan+linaro@...nel.org> wrote:
> > >
> > > This series fixes some of the fallout after a recent series adding
> > > support for DMA transfers to the Qualcomm geni serial driver.
> > >
> > > Most importantly it fixes a hang during reboot when using a serial
> > > console and the getty is stopped during reboot.
> > >
> > > Doug just posted an equivalent fix here:
> > >
> > >         https://lore.kernel.org/lkml/20230307073155.1.Iaab0159b8d268060a0e131ebb27125af4750ef99@changeid
> > >
> > > but the commit message only mentions the regression with respect to
> > > kgdb, which is not as widely used serial consoles generally, so I
> > > figured I'd post my version for completeness.
> > >
> > > Either version of that fix should address the immediate regression, but
> > > fixing the underlying problems which have been there since the driver
> > > was first merged is going to be a bit more involved.
> > >
> > > The rest of the series fixes a few bugs in the new DMA support that I
> > > found while investigating the console regression.
> > >
> > > Johan
> > >
> > >
> > > Johan Hovold (4):
> > >   serial: qcom-geni: fix console shutdown hang
> > >   serial: qcom-geni: fix DMA mapping leak on shutdown
> > >   serial: qcom-geni: fix mapping of empty DMA buffer
> > >   serial: qcom-geni: drop bogus uart_write_wakeup()
> > >
> > >  drivers/tty/serial/qcom_geni_serial.c | 11 +++++++----
> > >  1 file changed, 7 insertions(+), 4 deletions(-)
> > >
> > > --
> > > 2.39.2
> > >
> >
> > Hey Johan,
> >
> > Douglas and Srini beat you to these fixes but thanks!

> Nevermind, I read your other message now. And also patch 3/4 looks right.

Heh, this hang has been in linux-next for over a month and I've
actively tried to not spend time on investigating it in the hope that
someone else would be beat me to it before I moved to 6.3-rc. :)

Obviously I may be a bit biased, but I prefer this series over the
alternate fixes as the commit messages are a bit more complete and my
version of the empty DMA buffer fix is a bit cleaner.

Johan