linux-kernel - Re: [RFC PATCH -rcu lkmm] tools/memory-model/README: Expand dependency of klitmus7

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Date:   Wed, 3 Jun 2020 19:32:58 -0700
From:   "Paul E. McKenney" <paulmck@...nel.org>
To:     Andrea Parri <parri.andrea@...il.com>
Cc:     Akira Yokosawa <akiyks@...il.com>,
        Boqun Feng <boqun.feng@...il.com>,
        Jade Alglave <jade.alglave@....com>,
        Luc Maranget <luc.maranget@...ia.fr>,
        Joel Fernandes <joel@...lfernandes.org>,
        Alan Stern <stern@...land.harvard.edu>,
        Will Deacon <will@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Nicholas Piggin <npiggin@...il.com>,
        David Howells <dhowells@...hat.com>,
        Daniel Lustig <dlustig@...dia.com>,
        linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org
Subject: Re: [RFC PATCH -rcu lkmm] tools/memory-model/README: Expand
 dependency of klitmus7

On Mon, Jun 01, 2020 at 06:34:33AM +0200, Andrea Parri wrote:
> On Mon, Jun 01, 2020 at 12:37:20AM +0900, Akira Yokosawa wrote:
> > From 87048d7212f6cb16b0a2b85fa6d2f34c28b078c0 Mon Sep 17 00:00:00 2001
> > From: Akira Yokosawa <akiyks@...il.com>
> > Date: Sun, 31 May 2020 20:04:32 +0900
> > Subject: [PATCH RFC] tools/memory-model/README: Expand dependency of klitmus7
> > 
> > klitmus7 is independent of the memory model but depends on the
> > build-target kernel release.
> > It occasionally lost compatibility due to kernel API changes [1, 2, 3].
> > It was remedied in a backwards-compatible manner respectively [4, 5, 6].
> > 
> > Reflect this fact in README.
> > 
> > [1]: b899a850431e ("compiler.h: Remove ACCESS_ONCE()")
> > [2]: 0bb95f80a38f ("Makefile: Globally enable VLA warning")
> > [3]: d56c0d45f0e2 ("proc: decouple proc from VFS with "struct proc_ops"")
> > [4]: https://github.com/herd/herdtools7/commit/e87d7f9287d1
> >      ("klitmus: Use WRITE_ONCE and READ_ONCE in place of deprecated ACCESS_ONCE")
> > [5]: https://github.com/herd/herdtools7/commit/a0cbb10d02be
> >      ("klitmus: Avoid variable length array")
> > [6]: https://github.com/herd/herdtools7/commit/46b9412d3a58
> >      ("klitmus: Linux kernel v5.6.x compat")
> > 
> > NOTE: [5] was ahead of herdtools7 7.53, which did not make an
> > official release.  Code generated by klitmus7 without [5] can still be
> > built targeting Linux 4.20--5.5 if you don't care VLA warnings.
> > 
> > Signed-off-by: Akira Yokosawa <akiyks@...il.com>
> 
> Acked-by: Andrea Parri <parri.andrea@...il.com>

Queued, thank you both!

							Thanx, Paul

>   Andrea
> 
> 
> > ---
> > Hi all,
> > 
> > Recent struggle of Andrii with the use of klitmus7 on an up-to-date
> > Linux system prompted me to add some explanation of klitmus7's dependency
> > in README.
> > 
> > As herdtools7 7.56 is still under development, I called out just HEAD
> > in the compatibility table.  Once 7.56 is released, the table can be
> > updated.
> > 
> > I'm not sure if this is the right place to carry such info.
> > Anyway, I'd be glad if this patch can trigger a meaningful update of
> > README.
> > 
> >         Thanks, Akira
> > --
> >  tools/memory-model/README | 30 ++++++++++++++++++++++++++++--
> >  1 file changed, 28 insertions(+), 2 deletions(-)
> > 
> > diff --git a/tools/memory-model/README b/tools/memory-model/README
> > index b9c562e92981..90af203c3cf1 100644
> > --- a/tools/memory-model/README
> > +++ b/tools/memory-model/README
> > @@ -28,8 +28,34 @@ downloaded separately:
> >  See "herdtools7/INSTALL.md" for installation instructions.
> >  
> >  Note that although these tools usually provide backwards compatibility,
> > -this is not absolutely guaranteed.  Therefore, if a later version does
> > -not work, please try using the exact version called out above.
> > +this is not absolutely guaranteed.
> > +
> > +For example, a future version of herd7 might not work with the model
> > +in this release.  A compatible model will likely be made available in
> > +a later release of Linux kernel.
> > +
> > +If you absolutely need to run the model in this particular release,
> > +please try using the exact version called out above.
> > +
> > +klitmus7 is independent of the model provided here.  It has its own
> > +dependency on a target kernel release where converted code is built
> > +and executed.  Any change in kernel APIs essential to klitmus7 will
> > +necessitate an upgrade of klitmus7.
> > +
> > +If you find any compatibility issues in klitmus7, please inform the
> > +memory model maintainers.
> > +
> > +klitmus7 Compatibility Table
> > +----------------------------
> > +
> > +	============  ==========
> > +	target Linux  herdtools7
> > +	------------  ----------
> > +	     -- 4.18  7.48 --
> > +	4.15 -- 4.19  7.49 --
> > +	4.20 -- 5.5   7.54 --
> > +	5.6  --       HEAD
> > +	============  ==========
> >  
> >  
> >  ==================
> > -- 
> > 2.17.1
> >