linux-kernel - Re: [PATCH v2] tools/memory-model: Document herd7 (abstract) representation

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Message-ID: <010bd7e9-de81-4ff7-8532-18c41318123e@rowland.harvard.edu>
Date: Wed, 5 Jun 2024 13:55:08 -0400
From: Alan Stern <stern@...land.harvard.edu>
To: Andrea Parri <parri.andrea@...il.com>
Cc: will@...nel.org, peterz@...radead.org, boqun.feng@...il.com,
  npiggin@...il.com, dhowells@...hat.com, j.alglave@....ac.uk,
  luc.maranget@...ia.fr, paulmck@...nel.org, akiyks@...il.com,
  dlustig@...dia.com, joel@...lfernandes.org, linux-kernel@...r.kernel.org,
  linux-arch@...r.kernel.org, hernan.poncedeleon@...weicloud.com,
  jonas.oberhauser@...weicloud.com
Subject: Re: [PATCH v2] tools/memory-model: Document herd7 (abstract)
 representation

On Wed, Jun 05, 2024 at 06:52:18PM +0200, Andrea Parri wrote:
> > I wonder if we really need a special notation for lk-rmw.  Is anything 
> > wrong with using the normal rmw notation for these links?
> 
> I don't think we need the special notation: in fact, herd7 doesn't know
> anything about these lk-rmw or rmw links between lock events until after
> tools/memory-model/ (the .cat file) has established such links cf.
> 
>   (* Link Lock-Reads to their RMW-partner Lock-Writes *)
>   let lk-rmw = ([LKR] ; po-loc ; [LKW]) \ (po ; po)
>   let rmw = rmw | lk-rmw
> 
> I was trying to be informative (since that says "lk-rmw is a subrelation
> of rmw) but, in order to be faithful to the scope of this document (herd
> representation), the doc should really just indicate LKR ->po LKW.
> 
> Thoughts?

I agree; be faithful to the document's scope and just say LKR ->po LKW.

Were there other things like this in the table?  I didn't notice any.

Alan