linux-kernel - Re: [PATCH] iio: cros_ec_accel_legacy: Always release lock when returning from

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Message-ID: <CAD=FV=WT6TT+iyGVNUhNcmAsVJip6X4mytuNJPGwMkk4F4i75g@mail.gmail.com>
Date:   Mon, 15 Jul 2019 12:40:42 -0700
From:   Doug Anderson <dianders@...omium.org>
To:     Matthias Kaehlcke <mka@...omium.org>
Cc:     Jonathan Cameron <jic23@...nel.org>,
        Hartmut Knaack <knaack.h@....de>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Peter Meerwald-Stadler <pmeerw@...erw.net>,
        Benson Leung <bleung@...omium.org>,
        Enric Balletbo i Serra <enric.balletbo@...labora.com>,
        Guenter Roeck <groeck@...omium.org>,
        linux-iio <linux-iio@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Gwendal Grignou <gwendal@...omium.org>
Subject: Re: [PATCH] iio: cros_ec_accel_legacy: Always release lock when
 returning from _read()

Hi,

On Mon, Jul 15, 2019 at 12:10 PM Matthias Kaehlcke <mka@...omium.org> wrote:
>
> Before doing any actual work cros_ec_accel_legacy_read() acquires
> a mutex, which is released at the end of the function. However for
> 'calibbias' channels the function returns directly, without releasing
> the lock. The next attempt to acquire the lock blocks forever. Instead
> of an explicit return statement use the common return path, which
> releases the lock.
>
> Fixes: 11b86c7004ef1 ("platform/chrome: Add cros_ec_accel_legacy driver")
> Signed-off-by: Matthias Kaehlcke <mka@...omium.org>
> ---
>  drivers/iio/accel/cros_ec_accel_legacy.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)

See also <https://lkml.kernel.org/r/39403a4c-bf7f-6a98-890c-57397fa66493@collabora.com>

Actually, the "Fixes" tag is wrong here, though.  The problem only
exists because we have <https://crrev.com/c/1632659> in our tree, AKA
("FROMLIST: iio: cros_ec : Extend legacy support to ARM device").
Before that there was no mutex.  For upstream purposes this could
probably be squashed into the original patch.

-Doug