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McKenney" , linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, kernel-team@meta.com, boqun.feng@gmail.com, j.alglave@ucl.ac.uk, luc.maranget@inria.fr, Joel Fernandes Subject: Re: LKMM: Making RMW barriers explicit Message-ID: References: <2f20e7cf-7c67-4ad3-8a0c-3c1d01257ae4@rowland.harvard.edu> <0c309dd3-f8c1-4945-b8f1-154b2a775216@huaweicloud.com> <4286e5b2-5954-4c77-a815-c1c2735d9509@rowland.harvard.edu> <58042cf3-e515-4e5f-ab48-1d0d6123c9e9@huaweicloud.com> <6174fd09-b287-49ae-b117-c3a36ef3800a@rowland.harvard.edu> <73e08b17-cb2a-4e14-a94f-7144c5738684@huaweicloud.com> <1b1485f8-9c84-4221-b955-622dbf2fd953@huaweicloud.com> Precedence: bulk X-Mailing-List: linux-arch@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: <1b1485f8-9c84-4221-b955-622dbf2fd953@huaweicloud.com> > Do you mean the one example in Table 3? > What about cmpxchg() or cmpxchg_acquire()? Yes, Table 3. The cmpxchg*() primitives were not discussed in the paper. IIRC, their representation has not changed since at least 1c27b644c0fd. > We're definitely getting rid of some lines in herd7, that have been added > solely for dealing with this specific case of LKMM. Good. If the herd7 maintainers are "tired" of dealing with those lines, that's definitely a big fat "why" to put in a changelog. > Deal with what, no longer having to learn OCaml to be sure that the LKMM's > formal definition matches the description in memory_barriers.txt? Nope. ;-) Dealing with the review, testing, and maintainance of a new representation. > - it makes it easier to maintain the LKMM in the future, because you don't > have to work around hidden transformations inside herd7 > - it makes implicit behavior explicit > - it makes it easier to understand that the formalization matches the > intention > - it makes it easier to learn the LKMM from the formalization without having > to cross-reference every bit with the informal documentation to avoid > misunderstandings Jonas - You write "less hidden", "less implicit", but I keep reading "a representation I/some people would expect". We've already acknowledged that's no deciding factor to abandon the current seasoned representation. Andrea