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Date:   Wed, 5 Sep 2018 17:01:17 -0700
From:   "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
To:     Will Deacon <will.deacon@arm.com>
Cc:     linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org,
        stern@rowland.harvard.edu, andrea.parri@amarulasolutions.com,
        peterz@infradead.org, boqun.feng@gmail.com, npiggin@gmail.com,
        dhowells@redhat.com, j.alglave@ucl.ac.uk, luc.maranget@inria.fr,
        akiyks@gmail.com, mingo@kernel.org
Subject: Re: [PATCH RFC tools/memory-model] Add litmus-test naming scheme
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On Tue, May 29, 2018 at 09:17:13PM +0100, Will Deacon wrote:
> On Tue, May 29, 2018 at 05:11:07AM -0700, Paul E. McKenney wrote:
> > On Tue, May 29, 2018 at 10:30:50AM +0100, Will Deacon wrote:
> > > Hi Paul,
> > > 
> > > On Fri, May 25, 2018 at 12:10:20PM -0700, Paul E. McKenney wrote:
> > > > This commit documents the scheme used to generate the names for the
> > > > litmus tests.
> > > > 
> > > > Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
> > > > ---
> > > >  README |  136 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++-
> > > >  1 file changed, 135 insertions(+), 1 deletion(-)
> > > 
> > > Whilst I think documentation like this is extremely important for users,
> > > this feels like it's documenting how to drive parts of diy and I'm not
> > > convinced that it belongs in the kernel source tree as long as the projects
> > > remain separate.
> > > 
> > > Why not contribute this to the herdtools7 documentation, then just reference
> > > that from here? That would also be helpful for other people interested in
> > > memory models, but perhaps not interested in Linux (assuming such people
> > > exist ;).
> > 
> > We would still need at least a pointer from the Linux kernel to that
> > documentation, but I am happy either way.  We probably need examples of
> > the common cases, but probably not a full exposition of all the available
> > herd7 edges.
> 
> Completely agreed.
> 
> > Should this be in the herdtools7 documentation, or as added detail
> > from a variation on the "diyone7 -bell linux-kernel.bell -show edges"
> > command?  If the latter, I suppose that the ones coming from the .bell
> > file might simply be labelled as such.
> 
> Many of the edges aren't specific to the Linux kernel, so I think they
> should be part of the diyone7 documentation. We could then describe only
> the additional edges added by the kernel memory model (e.g. "Once") in
> the kernel documentation.

And there are a -lot- of them, and they are likely to change going
forward, both in herd7 and in linux-kernel.bell.  How about if I give
examples and say where they are from and how to get a list, as in the
following --squash commit to be merged with the orginal?

							Thanx, Paul

------------------------------------------------------------------------

commit e366b8cd832535894c55265c112355c4de9a3247
Author: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Date:   Wed Sep 5 15:38:00 2018 -0700

    squash! EXP tools/memory-model: Add litmus-test naming scheme
    
    Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
    [ paulmck: Apply feedback from Will Deacon. ]

diff --git a/tools/memory-model/litmus-tests/README b/tools/memory-model/litmus-tests/README
index 08c1116c0314..5ee08f129094 100644
--- a/tools/memory-model/litmus-tests/README
+++ b/tools/memory-model/litmus-tests/README
@@ -243,56 +243,11 @@ produce the name:
 
 Adding the ".litmus" suffix: SB+rfionceonce-poonceonces.litmus
 
+The descriptors that describe connections between consecutive accesses
+within the cycle through a given litmus test can be provided by the herd
+tool (Rfi, Po, Fre, and so on) or by the linux-kernel.bell file (Once,
+Release, Acquire, and so on).
 
-=======================
-LITMUS TEST DESCRIPTORS
-=======================
-
-These descriptors cover connections between consecutive accesses within
-the cycle through a given litmus test:
-
-Fre: From-read external.  The current process wrote a variable that
-	the previous process read.  Example: The SB (store buffering) test.
-Fri: From-read internal.  This process read a variable and then
-	immediately wrote to it.  Example: ???
-PodRR: Program-order different variable, read followed by read.
-	This process read a variable and again read a different variable.
-	Example: The read-side process in the MP (message-passing) test.
-PodRW: Program-order different variable, read followed by write.
-	This process read a variable and then wrote a different variable.
-	Example: The LB (load buffering) test.
-PodWR: Program-order different variable, write followed by read.
-	This process wrote a variable and then read a different variable.
-	Example: The SB (store buffering) test.
-PodWW: Program-order different variable, write followed by write.
-	This process wrote a variable and again wrote a different variable.
-	Example: The write-side process in the MP (message-passing) test.
-PosRR: Program-order same variable, read followed by read.
-	This process read a variable and again read that same variable.
-	Example: ???
-PosRW: Program-order same variable, read followed by write.
-	This process read a variable and then wrote that same variable.
-	Example: ???
-PosWR: Program-order same variable, write followed by read.
-	This process wrote a variable and then read that same variable.
-	Example: ???
-PosWW: Program-order same variable, write followed by write.
-	This process wrote a variable and again wrote that same variable.
-	Example: ???
-Rfe: Read-from external.  The current process read a variable written
-	by the previous process.  Example: The MP (message passing) test.
-Rfi: Read-from internal.  The current process wrote a variable and then
-	immediately read the value back from it.  For the purposes
-	of litmus-test code generation, Rfi acts identically to PosWR.
-	However, they differ for purposes of naming, and they also result
-	in different "exists" clauses.
-	Example:  ???
-Wse: Write same external.  The current process wrote to a variable that
-	was also written to by the previous process.  Example:  ???
-Wsi: Write same internal.  The current process wrote to a variable and
-	then immediately wrote to it again.  Example:  ???
-
-Please note that the above is a partial list.  To see the full list of
-descriptors, execute the following command:
+To see the full list of descriptors, execute the following command:
 
 	$ diyone7 -bell linux-kernel.bell -show edges