linux-kernel - Re: Prototype patch for Linux-kernel memory model

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Date:   Tue, 14 Nov 2017 08:59:25 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Cc:     stern@...land.harvard.edu, parri.andrea@...il.com,
        will.deacon@....com, boqun.feng@...il.com, npiggin@...il.com,
        dhowells@...hat.com, j.alglave@....ac.uk, luc.maranget@...ia.fr,
        linux-kernel@...r.kernel.org, elena.reshetova@...el.com
Subject: Re: Prototype patch for Linux-kernel memory model

On Mon, Nov 13, 2017 at 10:40:31AM -0800, Paul E. McKenney wrote:
> commit 82a1431549b4eae531e83298fd72cd0acea08540
> Author: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
> Date:   Mon Nov 13 10:30:07 2017 -0800
> 
>     tools: Automate memory-barriers.txt; provide Linux-kernel memory model
>     
>     There is some reason to believe that Documentation/memory-barriers.txt
>     could use some help, and a major purpose of this patch is to provide
>     that help in the form of a design-time tool that can produce all valid
>     executions of a small fragment of concurrent Linux-kernel code, which is
>     called a "litmus test".  This tool's functionality is roughly similar to
>     a full state-space search.  Please note that this is a design-time tool,
>     not useful for regression testing.  However, we hope that the underlying
>     Linux-kernel memory model will be incorporated into other tools capable
>     of analyzing large bodies of code for regression-testing purposes.
>     
>     The main tool is herd7, together with the linux-kernel.bell,
>     linux-kernel.cat, linux-kernel.cfg, linux-kernel.def, and lock.cat files
>     added by this patch.  The herd7 executable takes the other files as input,
>     and all of these files collectively define the Linux-kernel memory memory
>     model.  A brief description of each of these other files is provided
>     in the README file.  Although this tool does have its limitations,
>     which are documented in the README file, it does improve on the version
>     reported on in the LWN series (https://lwn.net/Articles/718628/ and
>     https://lwn.net/Articles/720550/) by supporting locking and arithmetic,
>     including a much wider variety of read-modify-write atomic operations.
>     Please note that herd7 is not part of this submission, but is freely
>     available from http://diy.inria.fr/sources/index.html (and via "git"
>     at https://github.com/herd/herdtools7).
>     
>     A second tool is klitmus7, which converts litmus tests to loadable
>     kernel modules for direct testing.  As with herd7, the klitmus7
>     code is freely available from http://diy.inria.fr/sources/index.html
>     (and via "git" at https://github.com/herd/herdtools7).
>     
>     Of course, litmus tests are not always the best way to fully understand a
>     memory model, so this patch also includes Documentation/explanation.txt,
>     which describes the memory model in detail.  In addition,
>     Documentation/recipes.txt provides example known-good and known-bad use
>     cases for those who prefer working by example.
>     
>     This patch also includes a few sample litmus tests, and a great many
>     more litmus tests are available at https://github.com/paulmckrcu/litmus.
>     
>     Signed-off-by: Alan Stern <stern@...land.harvard.edu>
>     Signed-off-by: Andrea Parri <parri.andrea@...il.com>
>     Signed-off-by: Will Deacon <will.deacon@....com>
>     Signed-off-by: Peter Zijlstra <peterz@...radead.org>
>     Signed-off-by: Boqun Feng <boqun.feng@...il.com>
>     Signed-off-by: Nicholas Piggin <npiggin@...il.com>
>     Signed-off-by: David Howells <dhowells@...hat.com>
>     Signed-off-by: Jade Alglave <j.alglave@....ac.uk>
>     Signed-off-by: Luc Maranget <luc.maranget@...ia.fr>
>     Signed-off-by: "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
>     Cc: <linux-arch@...r.kernel.org>

So I think that SoB chains like that are utter crap. I think you meant
to have all but the one from you be an Ack or similar.