linux-kernel - Re: [PATCH v4 4/7] ACPI: button: Use input_device

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Message-ID: <20201005050642.GH1009802@dtor-ws>
Date:   Sun, 4 Oct 2020 22:06:42 -0700
From:   Dmitry Torokhov <dmitry.torokhov@...il.com>
To:     Andrzej Pietrasiewicz <andrzej.p@...labora.com>
Cc:     linux-pm@...r.kernel.org, linux-acpi@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-iio@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-samsung-soc@...r.kernel.org, linux-input@...r.kernel.org,
        linux-tegra@...r.kernel.org, patches@...nsource.cirrus.com,
        ibm-acpi-devel@...ts.sourceforge.net,
        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>,
        kernel@...labora.com
Subject: Re: [PATCH v4 4/7] ACPI: button: Use input_device_enabled() helper

On Wed, Jun 24, 2020 at 10:24:46PM -0700, Dmitry Torokhov wrote:
> On Mon, Jun 08, 2020 at 01:22:08PM +0200, Andrzej Pietrasiewicz wrote:
> > A new helper is available, so use it.
> > 
> > Signed-off-by: Andrzej Pietrasiewicz <andrzej.p@...labora.com>
> > ---
> >  drivers/acpi/button.c | 4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/acpi/button.c b/drivers/acpi/button.c
> > index ff7ab291f678..4deb2b48d03c 100644
> > --- a/drivers/acpi/button.c
> > +++ b/drivers/acpi/button.c
> > @@ -411,7 +411,7 @@ static void acpi_button_notify(struct acpi_device *device, u32 event)
> >  		input = button->input;
> >  		if (button->type == ACPI_BUTTON_TYPE_LID) {
> >  			mutex_lock(&button->input->mutex);
> > -			users = button->input->users;
> > +			users = input_device_enabled(button->input);
> >  			mutex_unlock(&button->input->mutex);
> >  			if (users)
> 
> This chunk (pre-patch) is really wrong. 'users' value is obsolete and
> can not be trusted the moment we unlocked the mutex. "if" needs to be
> inside critical section.

So looking at this patch and the previous one again, I believe this
driver is wrong to key the behavior off input->users and we should not
apply either of the patches. I'll post another patch fixing this.

Thanks.

-- 
Dmitry