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Message-ID: <41bc01fa-ce02-4005-a3c2-abfabe1c6927@huaweicloud.com>
Date: Mon, 27 May 2024 15:40:13 +0200
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Subject: Re: [PATCH] tools/memory-model: Document herd7 (internal)
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To: Andrea Parri <parri.andrea@gmail.com>,
 Hernan Ponce de Leon <hernan.poncedeleon@huaweicloud.com>
Cc: stern@rowland.harvard.edu, 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, paulmck@kernel.org,
 akiyks@gmail.com, dlustig@nvidia.com, joel@joelfernandes.org,
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References: <20240524151356.236071-1-parri.andrea@gmail.com>
 <1a3c892c-903e-8fd3-24a6-2454c2a55302@huaweicloud.com>
 <ZlSKYA/Y/daiXzfy@andrea>
From: Jonas Oberhauser <jonas.oberhauser@huaweicloud.com>
In-Reply-To: <ZlSKYA/Y/daiXzfy@andrea>
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Am 5/27/2024 um 3:28 PM schrieb Andrea Parri:
>>> +    |                smp_store_mb | W[once] ->po F[mb]                        |
>>
>> I expect this one to be hard-coded in herd7 source code, but I cannot find
>> it. Can you give me a pointer?
> 
> smp_store_mb() is currently mapped to { __store{once}(X,V); __fence{mb}; } in
> the .def file, so it's semantically equivalent to "WRITE_ONCE(); smp_mb();".

By the way, I experimented a little with these kind of mappings to see 
if we can just explicitly encode the mapping there. E.g., I had an idea 
to use
     { __fence{mb-successful-rmw}; __cmpxchg{once}...; 
__fence{mb-successful-rmw}; }

for defining (almost) the current mapping of cmpxchg explicitly.

But none of the changes I made were accepted by herd7.

Do you know how the syntax works?

     jonas