linux-kernel - Re: [GIT PULL tools] Linux kernel memory model

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Date:   Thu, 1 Feb 2018 21:40:13 -0800
From:   "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:     Boqun Feng <boqun.feng@...il.com>
Cc:     Ingo Molnar <mingo@...nel.org>, linux-kernel@...r.kernel.org,
        linux-arch@...r.kernel.org, stern@...land.harvard.edu,
        parri.andrea@...il.com, j.alglave@....ac.uk, luc.maranget@...ia.fr,
        will.deacon@....com, peterz@...radead.org, npiggin@...il.com,
        dhowells@...hat.com, elena.reshetova@...el.com, mhocko@...e.com,
        akiyks@...il.com, Thomas Gleixner <tglx@...utronix.de>,
        Peter Zijlstra <a.p.zijlstra@...llo.nl>,
        Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [GIT PULL tools] Linux kernel memory model

On Fri, Feb 02, 2018 at 12:46:03PM +0800, Boqun Feng wrote:
> On Wed, Jan 31, 2018 at 05:17:28PM -0800, Paul E. McKenney wrote:
> [...]
> > > - A long term question: have you considered and would it make sense to generate a
> > >   memory-barriers.txt like file directly into Documentation/locking/, using the
> > >   formal description? That way any changes/extensions/fixes to the model could be
> > >   tracked on a high level, without readers having to understand the formal
> > >   representation.
> > 
> > I hadn't considered this at all, actually.  ;-)
> > 
> > The sections of memory-barriers.txt dealing with MMIO ordering would need
> > to stay hand-generated, but they are a very small fraction of the total.
> > The herd7 tool is capable of generating cool diagrams sort of like
> > this one: https://static.lwn.net/images/2017/mm-model/rmo-acyclic.png,
> > which might replace at least some of the hand-generated ASCII-art
> > diagrams.
> 
> Which reminds me, one thing we could start with is to try to convert all
> the examples with litmus tests. Has this been done somewhere (e.g. in
> your litmus github repo)? If not, I can try if you think that's a good
> idea.

That would be very helpful, thank you!

There are probably some that are already in the litmus-tests directory,
but I suspect that most are not yet converted.  So please do!

							Thanx, Paul

> Regards,
> Boqun
> 
> > Although I do confess harboring some skepticism about being able to
> > generated high-quality text, there is no denying that it would be
> > valuable to be able to do so.
> > 
> > > In any case, the base commit is certainly nice and clean and I've pulled it into 
> > > tip:locking/core for a v4.17 merge.
> > 
> > Very good!
> > 
> > > I believe these additional improvements (to the extent you agree with doing them!) 
> > > could/should be done as add-on commits on top of this existing commit.
> > 
> > Sounds good!
> > 
> > Would you prefer a pull request or a patch series for these?
> > 
> > 							Thanx, Paul
> >