linux-kernel - Re: [PATCH v15 00/13] mux controller abstraction and iio/i2c muxes

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Date:   Sat, 3 Jun 2017 20:37:21 +0200
From:   Luc Van Oostenryck <luc.vanoostenryck@...il.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Peter Rosin <peda@...ator.liu.se>,
        open list <linux-kernel@...r.kernel.org>,
        Peter Rosin <peda@...ntia.se>,
        Wolfram Sang <wsa@...-dreams.de>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Jonathan Cameron <jic23@...nel.org>,
        Hartmut Knaack <knaack.h@....de>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Peter Meerwald-Stadler <pmeerw@...erw.net>,
        Jonathan Corbet <corbet@....net>, linux-i2c@...r.kernel.org,
        devicetree@...r.kernel.org, linux-iio@...r.kernel.org,
        linux-doc@...r.kernel.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        Colin Ian King <colin.king@...onical.com>,
        Paul Gortmaker <paul.gortmaker@...driver.com>,
        Philipp Zabel <p.zabel@...gutronix.de>, kernel@...gutronix.de
Subject: Re: [PATCH v15 00/13] mux controller abstraction and iio/i2c muxes

On Sat, Jun 3, 2017 at 12:26 PM, Greg Kroah-Hartman
<gregkh@...uxfoundation.org> wrote:
> On Sun, May 14, 2017 at 09:51:03PM +0200, Peter Rosin wrote:
>> From: Peter Rosin <peda@...ntia.se>
>>
>> Hi Greg,
>>
>> Philipp found problems in v14 with using a mutex for locking that was
>> the outcome of the review for v13, so I'm now using a semaphore instead
>> of the rwsem that was in v13. That at least got rid of the scary call
>> to downgrade_write. However, I'm still unsure about what you actually
>> meant with your comment about lack of sparse markings [1]. I did add
>> __must_check to the funcs that selects the mux, but I've got this
>> feeling that this is not what you meant?
>
> I thought there was a way to mark a function as requiring a lock be held
> when it is being called.  Does sparse not support that anymore?

sparse still support these annotations, of course.
In this case, I suppose you're talking about '__must_hold()' which
*must* be used instead of a pair of '__releases()' + '__acquires()'
when the lock is help on function entry and exit.

Cheers,
-- Luc Van Oostenryck