linux-kernel - Re: [PATCH] Documentation/memory-barriers: fix wrong comment in example

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Message-ID: <CAEjAshpv38QjxHLx4puHKmFd7=63SJqe=aQtv6n1_wVOKGutbA@mail.gmail.com>
Date:	Tue, 23 Feb 2016 06:45:32 +0900
From:	SeongJae Park <sj38.park@...il.com>
To:	Paul McKenney <paulmck@...ux.vnet.ibm.com>
Cc:	David Howells <dhowells@...hat.com>,
	Jonathan Corbet <corbet@....net>,
	linux-doc <linux-doc@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] Documentation/memory-barriers: fix wrong comment in example

On Tue, Feb 23, 2016 at 1:33 AM, Paul E. McKenney
<paulmck@...ux.vnet.ibm.com> wrote:
> On Mon, Feb 22, 2016 at 11:16:39AM +0000, David Howells wrote:
>> SeongJae Park <sj38.park@...il.com> wrote:
>>
>> > From f7b5677790771599f418f1d95536935be971ae86 Mon Sep 17 00:00:00 2001
>> > From: SeongJae Park <sj38.park@...il.com>
>> > Date: Mon, 22 Feb 2016 19:26:18 +0900
>> > Subject: [PATCH] Documentation/memory-barriers: polish compiler store omit
>> >  example
>> >
>> > Comments of examples about compiler store omit in memory-barriers.txt is
>> > about code that could be possible at that point.  However, someone could
>> > interpret the comment as an explanation about below line.  This commit
>> > exploits the intent more explicitly by changing the comment to be seems
>> > like a possible code rather than explanation about below line.
>> >
>> > Signed-off-by: SeongJae Park <sj38.park@...il.com>
>> > ---
>> >  Documentation/memory-barriers.txt | 4 ++--
>> >  1 file changed, 2 insertions(+), 2 deletions(-)
>> >
>> > diff --git a/Documentation/memory-barriers.txt
>> > b/Documentation/memory-barriers.txt
>> > index 904ee42..dc66351 100644
>> > --- a/Documentation/memory-barriers.txt
>> > +++ b/Documentation/memory-barriers.txt
>> > @@ -1459,7 +1459,7 @@ of optimizations:
>> >       the following:
>> >
>> >         a = 0;
>> > -       /* Code that does not store to variable a. */
>> > +       ... Code that does not store to variable a ...
>> >         a = 0;
>> >
>> >       The compiler sees that the value of variable 'a' is already zero, so
>> > @@ -1471,7 +1471,7 @@ of optimizations:
>> >       wrong guess:
>> >
>> >         WRITE_ONCE(a, 0);
>> > -       /* Code that does not store to variable a. */
>> > +       ... Code that does not store to variable a ...
>> >         WRITE_ONCE(a, 0);
>> >
>> >   (*) The compiler is within its rights to reorder memory accesses unless
>>
>> Acked-by: David Howells <dhowells@...hat.com>
>
> Thank you both!  Patch with updated commit log below, please let me know
> if you have any objections to the changes.

Looks good to me :)


Thanks,
SeongJae Park

>
>                                                         Thanx, Paul
>
> ------------------------------------------------------------------------
>
> commit 0a41feb6ab4da3218192e2cde1a54fcc5d8f5658
> Author: SeongJae Park <sj38.park@...il.com>
> Date:   Mon Feb 22 08:28:29 2016 -0800
>
>     documentation: Clarify compiler store-fusion example
>
>     The compiler store-fusion example in memory-barriers.txt uses a C
>     comment to represent arbitrary code that does not update a given
>     variable.  Unfortunately, someone could reasonably interpret the
>     comment as instead referring to the following line of code.  This
>     commit therefore replaces the comment with a string that more
>     clearly represents the arbitrary code.
>
>     Signed-off-by: SeongJae Park <sj38.park@...il.com>
>     Acked-by: David Howells <dhowells@...hat.com>
>     Signed-off-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
>
> diff --git a/Documentation/memory-barriers.txt b/Documentation/memory-barriers.txt
> index 8367d393cba2..3729cbe60e41 100644
> --- a/Documentation/memory-barriers.txt
> +++ b/Documentation/memory-barriers.txt
> @@ -1550,7 +1550,7 @@ of optimizations:
>       the following:
>
>         a = 0;
> -       /* Code that does not store to variable a. */
> +       ... Code that does not store to variable a ...
>         a = 0;
>
>       The compiler sees that the value of variable 'a' is already zero, so
> @@ -1562,7 +1562,7 @@ of optimizations:
>       wrong guess:
>
>         WRITE_ONCE(a, 0);
> -       /* Code that does not store to variable a. */
> +       ... Code that does not store to variable a ...
>         WRITE_ONCE(a, 0);
>
>   (*) The compiler is within its rights to reorder memory accesses unless
>