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

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Message-ID: <20190715195023.GS250418@google.com>
Date:   Mon, 15 Jul 2019 12:50:23 -0700
From:   Matthias Kaehlcke <mka@...omium.org>
To:     Doug Anderson <dianders@...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()

On Mon, Jul 15, 2019 at 12:40:42PM -0700, Doug Anderson wrote:
> 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.

Oops, I didn't realize that upstream doesn't have the mutex. In this
case the entire patch as is with it's commit message doesn't make much
sense.