Date:   Sun, 29 Jan 2023 18:11:12 +0100
From:   Andrea Parri <parri.andrea@gmail.com>
To:     Alan Stern <stern@rowland.harvard.edu>
Cc:     Jonas Oberhauser <jonas.oberhauser@huaweicloud.com>,
        paulmck@kernel.org, will@kernel.org, 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,
        dlustig@nvidia.com, joel@joelfernandes.org, urezki@gmail.com,
        quic_neeraju@quicinc.com, frederic@kernel.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 2/2] tools/memory-model: Make ppo a subrelation of po
Message-ID: <Y9aoA2UxvWyNwOtx@andrea>
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> The reason why Wx=1 ->ww-vis Wx=2:
> 
> 	0:Wx=1 ->po-rel 0:Wy=1 and po-rel < fence < ww-post-bounded.
> 
> 	0:Wy=1 ->rfe 1:Ry=1 ->(hb* & int) 1:Rdy=1 and
> 		(rfe ; hb* & int) <= (rfe ; xbstar & int) <= vis.
> 
> 	1:Rdy=1 ->po 1:unlock ->rfe 3:lock ->po 3:Wx=2
> 		so 1:Rdy=1 ->po-unlock-lock-po 3:Wx=2
> 		and po-unlock-lock-po <= mb <= fence <= w-pre-bounded.
> 
> Finally, w-post-bounded ; vis ; w-pre-bounded <= ww-vis.

To clarify, po-unlock-lock-po is not a subrelation of mb; see what
happens without the smp_mb__after_unlock_lock().

  Andrea