linux-kernel - Re: [PATCH v2] HID: Replace semaphore driver

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Message-ID: <CANq1E4Two8-Qk5q=OFunE-mfuHvopY1Hm=7CrVZUaHJzBPUPyQ@mail.gmail.com>
Date:   Tue, 13 Jun 2017 17:43:52 +0200
From:   David Herrmann <dh.herrmann@...il.com>
To:     Benjamin Tissoires <benjamin.tissoires@...hat.com>
Cc:     Arnd Bergmann <arnd@...db.de>,
        Binoy Jayan <binoy.jayan@...aro.org>,
        "open list:HID CORE LAYER" <linux-input@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Rajendra <rnayak@...eaurora.org>,
        Mark Brown <broonie@...nel.org>,
        Jiri Kosina <jikos@...nel.org>,
        David Herrmann <dh.herrmann@...glemail.com>,
        Andrew de los Reyes <adlr@...omium.org>
Subject: Re: [PATCH v2] HID: Replace semaphore driver_lock with mutex

Hi

On Tue, Jun 13, 2017 at 11:56 AM, Benjamin Tissoires
<benjamin.tissoires@...hat.com> wrote:
>> > -       struct semaphore driver_lock;                                   /* protects the current driver, except during input */
>> > +       struct mutex driver_lock;                                       /* protects the current driver, except during input */
>> >         struct semaphore driver_input_lock;                             /* protects the current driver */
>
> Unless I am mistaken, this one could also be converted to a mutex (in a
> separate patch, of course).

The mutex code clearly states mutex_trylock() must not be used in
interrupt context (see kernel/locking/mutex.c), hence we used a
semaphore here. Unless the mutex code is changed to allow this, we
cannot switch away from semaphores.

Otherwise, this patch (given Benjamin's comments are addressed) looks good:

Reviewed-by: David Herrmann <dh.herrmann@...il.com>

Thanks
David