linux-kernel - Re: [PATCH v2 2/2] tools/memory-model: Make ppo a subrelation of po

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Date:   Sat, 28 Jan 2023 23:21:43 +0100
From:   Andrea Parri <parri.andrea@...il.com>
To:     Alan Stern <stern@...land.harvard.edu>
Cc:     Jonas Oberhauser <jonas.oberhauser@...weicloud.com>,
        paulmck@...nel.org, will@...nel.org, peterz@...radead.org,
        boqun.feng@...il.com, npiggin@...il.com, dhowells@...hat.com,
        j.alglave@....ac.uk, luc.maranget@...ia.fr, akiyks@...il.com,
        dlustig@...dia.com, joel@...lfernandes.org, urezki@...il.com,
        quic_neeraju@...cinc.com, frederic@...nel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/2] tools/memory-model: Make ppo a subrelation of po

On Sat, Jan 28, 2023 at 11:14:17PM +0100, Andrea Parri wrote:
> > Evidently the plain-coherence check rules out x=1 at the 
> > end, because when I relax that check, x=1 becomes a possible result.  
> > Furthermore, the graphical output confirms that this execution has a 
> > ww-incoh edge from Wx=2 to Wx=1.  But there is no ww-vis edge from Wx=1 
> > to Wx=2!  How can this be possible?  It seems like a bug in herd7.
> 
> By default, herd7 performs some edges removal when generating the
> graphical outputs.  The option -showraw can be useful to increase
> the "verbosity", for example,
> 
>   [with "exists (x=2)", output in /tmp/T.dot]

This was meant to be "exists (x=1)".

  Andrea


>   $ herd7 -conf linux-kernel.cfg T.litmus -show prop -o /tmp -skipchecks plain-coherence -doshow ww-vis -showraw ww-vis
> 
> 
> > Furthermore, the execution with x=2 at the end doesn't have either a 
> > ww-vis or a ww-nonrace edge betwen Wx=1 and Wx=2.  So why isn't there a 
> > ww-race edge?
> 
> And similarly
> 
>   [with "exists (x=2)"]
>   $ herd7 -conf linux-kernel.cfg T.litmus -show prop -o /tmp -doshow ww-vis,ww-nonrace -showraw ww-vis,ww-nonrace
> 
>   Andrea