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[103.168.172.200]) by smtp.gmail.com with ESMTPSA id af79cd13be357-794abca7f80sm402204585a.21.2024.05.28.10.59.34 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 28 May 2024 10:59:49 -0700 (PDT) Received: from compute5.internal (compute5.nyi.internal [10.202.2.45]) by mailfauth.nyi.internal (Postfix) with ESMTP id 7C4721200032; Tue, 28 May 2024 13:59:33 -0400 (EDT) Received: from mailfrontend2 ([10.202.2.163]) by compute5.internal (MEProxy); Tue, 28 May 2024 13:59:33 -0400 X-ME-Sender: X-ME-Received: X-ME-Proxy-Cause: gggruggvucftvghtrhhoucdtuddrgedvledrvdejkedgledvucetufdoteggodetrfdotf fvucfrrhhofhhilhgvmecuhfgrshhtofgrihhlpdfqfgfvpdfurfetoffkrfgpnffqhgen uceurghilhhouhhtmecufedttdenucesvcftvggtihhpihgvnhhtshculddquddttddmne cujfgurhepfffhvfevuffkfhggtggujgesthdtrodttddtvdenucfhrhhomhepuehoqhhu nhcuhfgvnhhguceosghoqhhunhdrfhgvnhhgsehgmhgrihhlrdgtohhmqeenucggtffrrg htthgvrhhnpeeitdefvefhteeklefgtefhgeelkeefffelvdevhfehueektdevhfettddv teevvdenucevlhhushhtvghrufhiiigvpedtnecurfgrrhgrmhepmhgrihhlfhhrohhmpe gsohhquhhnodhmvghsmhhtphgruhhthhhpvghrshhonhgrlhhithihqdeiledvgeehtdei gedqudejjeekheehhedvqdgsohhquhhnrdhfvghngheppehgmhgrihhlrdgtohhmsehfih igmhgvrdhnrghmvg X-ME-Proxy: Feedback-ID: iad51458e:Fastmail Received: by mail.messagingengine.com (Postfix) with ESMTPA; Tue, 28 May 2024 13:59:32 -0400 (EDT) Date: Tue, 28 May 2024 10:58:53 -0700 From: Boqun Feng To: Jonas Oberhauser Cc: Andrea Parri , Hernan Ponce de Leon , stern@rowland.harvard.edu, will@kernel.org, peterz@infradead.org, 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, linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org Subject: Re: [PATCH] tools/memory-model: Document herd7 (internal) representation Message-ID: References: <20240524151356.236071-1-parri.andrea@gmail.com> <1a3c892c-903e-8fd3-24a6-2454c2a55302@huaweicloud.com> <41bc01fa-ce02-4005-a3c2-abfabe1c6927@huaweicloud.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <41bc01fa-ce02-4005-a3c2-abfabe1c6927@huaweicloud.com> On Mon, May 27, 2024 at 03:40:13PM +0200, Jonas Oberhauser wrote: > > > 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? > This may not be trivial. Note that cmpxchg() is an expression (it has a value), so in .def, we want to define it as an expression. However, the C-like multiple-statement expression is not supported by herd parser, in other words we want: { __fence{mb-successful-rmw}; int tmp = __cmpxchg{once}(...); __fence{mb-successful-rmw}; tmp; } but herd parser doesn't support this as a valid expression. Regards, Boqun > jonas >