linux-kernel - Re: [PATCH v4 3/7] ACPI: button: Access input device's users under appropriate mutex

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Date:   Wed, 24 Jun 2020 22:23:18 -0700
From:   Dmitry Torokhov <dmitry.torokhov@...il.com>
To:     "Rafael J. Wysocki" <rafael@...nel.org>
Cc:     Andrzej Pietrasiewicz <andrzej.p@...labora.com>,
        Linux PM <linux-pm@...r.kernel.org>,
        ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-iio@...r.kernel.org,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Linux Samsung SoC <linux-samsung-soc@...r.kernel.org>,
        linux-input@...r.kernel.org,
        linux-tegra <linux-tegra@...r.kernel.org>,
        patches@...nsource.cirrus.com,
        ibm-acpi-devel@...ts.sourceforge.net,
        Platform Driver <platform-driver-x86@...r.kernel.org>,
        "Rafael J . Wysocki" <rjw@...ysocki.net>,
        Len Brown <lenb@...nel.org>,
        Jonathan Cameron <jic23@...nel.org>,
        Hartmut Knaack <knaack.h@....de>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Peter Meerwald-Stadler <pmeerw@...erw.net>,
        Kukjin Kim <kgene@...nel.org>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        Shawn Guo <shawnguo@...nel.org>,
        Sascha Hauer <s.hauer@...gutronix.de>,
        Pengutronix Kernel Team <kernel@...gutronix.de>,
        Fabio Estevam <festevam@...il.com>,
        NXP Linux Team <linux-imx@....com>,
        Vladimir Zapolskiy <vz@...ia.com>,
        Sylvain Lemieux <slemieux.tyco@...il.com>,
        Laxman Dewangan <ldewangan@...dia.com>,
        Thierry Reding <thierry.reding@...il.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        Barry Song <baohua@...nel.org>,
        Michael Hennerich <michael.hennerich@...log.com>,
        Nick Dyer <nick@...anahar.org>,
        Hans de Goede <hdegoede@...hat.com>,
        Ferruh Yigit <fery@...ress.com>,
        Sangwon Jee <jeesw@...fas.com>,
        Peter Hutterer <peter.hutterer@...hat.com>,
        Henrique de Moraes Holschuh <ibm-acpi@....eng.br>,
        Collabora Kernel ML <kernel@...labora.com>
Subject: Re: [PATCH v4 3/7] ACPI: button: Access input device's users under
 appropriate mutex

On Wed, Jun 24, 2020 at 05:00:09PM +0200, Rafael J. Wysocki wrote:
> On Mon, Jun 8, 2020 at 1:22 PM Andrzej Pietrasiewicz
> <andrzej.p@...labora.com> wrote:
> >
> > Inspecting input device's 'users' member should be done under device's
> > mutex, so add appropriate invocations.
> >
> > Signed-off-by: Andrzej Pietrasiewicz <andrzej.p@...labora.com>
> 
> This looks like a fix that might be applied independently of the other
> patches in the series.
> 
> Do you want me to pick it up?

If you pick it we'll have to have a dance with this series. Can I apply
instead?

I do not think this change has any practical effect as nobody
attaches/detached input handlers or opening/closing input devices when
system goes through device resume phase.

> 
> > ---
> >  drivers/acpi/button.c | 5 ++++-
> >  1 file changed, 4 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/acpi/button.c b/drivers/acpi/button.c
> > index 78cfc70cb320..ff7ab291f678 100644
> > --- a/drivers/acpi/button.c
> > +++ b/drivers/acpi/button.c
> > @@ -456,13 +456,16 @@ static int acpi_button_resume(struct device *dev)
> >  {
> >         struct acpi_device *device = to_acpi_device(dev);
> >         struct acpi_button *button = acpi_driver_data(device);
> > +       struct input_dev *input = button->input;
> >
> >         button->suspended = false;
> > -       if (button->type == ACPI_BUTTON_TYPE_LID && button->input->users) {
> > +       mutex_lock(&input->mutex);
> > +       if (button->type == ACPI_BUTTON_TYPE_LID && input->users) {
> >                 button->last_state = !!acpi_lid_evaluate_state(device);
> >                 button->last_time = ktime_get();
> >                 acpi_lid_initialize_state(device);
> >         }
> > +       mutex_unlock(&input->mutex);
> >         return 0;
> >  }
> >  #endif
> > --
> > 2.17.1
> >

Thanks.

-- 
Dmitry