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

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Message-ID: <20170603193445.GA18851@kroah.com>
Date:   Sat, 3 Jun 2017 21:34:45 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Luc Van Oostenryck <luc.vanoostenryck@...il.com>
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 03, 2017 at 08:37:21PM +0200, Luc Van Oostenryck wrote:
> 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.

Ah, yes, that's what I was thinking of.  I don't know if sparse can
track things like this across an exported symbol, so I doubt it really
will help here.  Sorry for the noise.

thanks,

greg k-h