linux-kernel - Re: [PATCH v4 3/4] device property: constify property arrays values

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Date:   Thu, 2 Feb 2017 16:16:48 -0800
From:   Dmitry Torokhov <dmitry.torokhov@...il.com>
To:     "Rafael J. Wysocki" <rafael@...nel.org>
Cc:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Joe Perches <joe@...ches.com>,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
        ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Mika Westerberg <mika.westerberg@...ux.intel.com>,
        Hans de Goede <hdegoede@...hat.com>,
        Wolfram Sang <wsa@...-dreams.de>
Subject: Re: [PATCH v4 3/4] device property: constify property arrays values

On Fri, Feb 03, 2017 at 12:16:29AM +0100, Rafael J. Wysocki wrote:
> On Thu, Feb 2, 2017 at 7:38 PM, Dmitry Torokhov
> <dmitry.torokhov@...il.com> wrote:
> > On Thu, Feb 02, 2017 at 07:52:58PM +0200, Andy Shevchenko wrote:
> >> On Thu, 2017-02-02 at 09:07 -0800, Dmitry Torokhov wrote:
> >> > On February 2, 2017 8:48:30 AM PST, Andy Shevchenko <andriy.shevchenko
> >> > @linux.intel.com> wrote:
> >> > > On Thu, 2017-02-02 at 08:39 -0800, Dmitry Torokhov wrote:
> >> > > > From: Dmitry Torokhov <dmitry.torokhov@...il.com>
> >> > > >
> >> > > > Data that is fed into property arrays should not be modified, so
> >> > >
> >> > > let's
> >> > > > mark
> >> > > > relevant pointers as const. This will allow us making source
> >> > > > arrays
> >> > >
> >> > > as
> >> > > > const/__initconst.
> >> > > >
> >> > > > Also fix memory leaks on errors in property_entry_copy().
> >> > >
> >> > > While the code looks okay, I'm not sure what memory leaks you are
> >> > > referring to. The idea as far as I remember was to run *free()
> >> > > function
> >> > > if *copy() fails.
> >> >
> >> > That could have been OK for internal function, but will not work for
> >> > public API, as it goes against normal pattern.
> 
> But it is an internal function, isn't it?
> 
> Also its only caller does the right thing AFAICS.

No, actually property_entries_dup() does not do the right thing anymore
:(.

> 
> >> > You will be old and grey and still correcting patches that would be
> >> > getting it wrong :)
> >>
> >> Yes, which sounds not exactly as "we have memory leaks and here we are
> >> fixing them". So, my comment regarding to phrasing of the commit
> >> message. Someone might mistakenly think that it needs to be ported as
> >> earlier as this had been introduced.
> >
> > OK, I'll leave it up to Rafael to massage the commit message as he sees
> > fit.
> 
> To be precise, there are no memory leaks and this is just adding an
> unnecessary label along with some code around it, equally unnecessary.
> 
> Are you planning on making property_entry_copy() non-static?

Maybe, but not yet. Still, I am uncomfortable with functions not
cleaning up but rather requiring leaving failed property structure in
such state that cleanup function will not crash on it. I think it is
fragile and I'd rather rework it so we clean up on the spot.

Thanks.

-- 
Dmitry