linux-kernel - Re: [PATCH] docs: lockdep-design: correct the notation for writer

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Date:   Mon, 24 May 2021 12:24:00 +0800
From:   Xiongwei Song <sxwjean@...il.com>
To:     Waiman Long <llong@...hat.com>
Cc:     Xiongwei Song <sxwjean@...com>, peterz@...radead.org,
        mingo@...hat.com, will@...nel.org, boqun.feng@...il.com,
        corbet@....net,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-doc@...r.kernel.org
Subject: Re: [PATCH] docs: lockdep-design: correct the notation for writer

On Fri, May 21, 2021 at 11:17 PM Waiman Long <llong@...hat.com> wrote:
>
> On 5/21/21 2:29 AM, Xiongwei Song wrote:
> > From: Xiongwei Song <sxwjean@...il.com>
> >
> > The block condition matrix is using 'E' as the writer noation here, so it
> > would be better to use 'E' as the reminder rather than 'W'.
> >
> > Signed-off-by: Xiongwei Song <sxwjean@...il.com>
> > ---
> >   Documentation/locking/lockdep-design.rst | 2 +-
> >   1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/Documentation/locking/lockdep-design.rst b/Documentation/locking/lockdep-design.rst
> > index 9f3cfca..c3b923a 100644
> > --- a/Documentation/locking/lockdep-design.rst
> > +++ b/Documentation/locking/lockdep-design.rst
> > @@ -462,7 +462,7 @@ Block condition matrix, Y means the row blocks the column, and N means otherwise
> >       | R | Y | Y | N |
> >       +---+---+---+---+
> >
> > -     (W: writers, r: non-recursive readers, R: recursive readers)
> > +     (E: writers, r: non-recursive readers, R: recursive readers)
> >
> >
> >   acquired recursively. Unlike non-recursive read locks, recursive read locks
>
> I would say it should be the other way around. Both W and E refer to the
> same type of lockers. W emphasizes writer aspect of it and E for
> exclusive. I think we should change the block condition matrix to use W
> instead of E.

The doc uses 'E'  to describe dependency egdes too. Should we change them
to 'W'? Personally,  both 'W' and 'E' are fine.

Thanks,
Xiongwei
>
> Cheers,
> Longman
>