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[172.10.233.147]) by smtp.gmail.com with ESMTPSA id q131-20020a817589000000b00565eb8af1fesm2009195ywc.132.2023.06.27.13.53.18 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 27 Jun 2023 13:53:21 -0700 (PDT) Date: Tue, 27 Jun 2023 13:53:17 -0700 (PDT) From: Hugh Dickins X-X-Sender: hugh@ripple.attlocal.net To: Jason Gunthorpe cc: Hugh Dickins , Andrew Morton , Gerald Schaefer , Vasily Gorbik , Mike Kravetz , Mike Rapoport , "Kirill A. Shutemov" , Matthew Wilcox , David Hildenbrand , Suren Baghdasaryan , Qi Zheng , Yang Shi , Mel Gorman , Peter Xu , Peter Zijlstra , Will Deacon , Yu Zhao , Alistair Popple , Ralph Campbell , Ira Weiny , Steven Price , SeongJae Park , Lorenzo Stoakes , Huang Ying , Naoya Horiguchi , Christophe Leroy , Zack Rusin , Axel Rasmussen , Anshuman Khandual , Pasha Tatashin , Miaohe Lin , Minchan Kim , Christoph Hellwig , Song Liu , Thomas Hellstrom , Russell King , "David Sc. Miller" , Michael Ellerman , "Aneesh Kumar K.V" , Heiko Carstens , Christian Borntraeger , Claudio Imbrenda , Alexander Gordeev , Jann Horn , Vishal Moola , Vlastimil Babka , linux-arm-kernel@lists.infradead.org, sparclinux@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH v2 05/12] powerpc: add pte_free_defer() for pgtables sharing page In-Reply-To: Message-ID: <7b1be7d-9287-cbc6-ef7-55e44625e4e@google.com> References: <54cb04f-3762-987f-8294-91dafd8ebfb0@google.com> <5cd9f442-61da-4c3d-eca-b7f44d22aa5f@google.com> <2ad8b6cf-692a-ff89-ecc-586c20c5e07f@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII X-Rspam-User: X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 3E46540015 X-Stat-Signature: wfz64s865xzp9pctp6zdbb9f3t55f653 X-HE-Tag: 1687899202-949692 X-HE-Meta: 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 9BVJgFmO 4qULfdR2UR9+fq5iH4EWn6RLH+lAhuT/1jAk1Cr3YDoZn4MK4BFVPQs37+PxykCO6I2Q17eczsEztR4ityTfe2/vCRHI4YYZc6cF5TyKUR9TKGZreQCu7pIzZuTAVIPShk0DwXsoaagPE6lUvv5I+FQTE40/u+HdgmdHolYnW4rps3JznwD1smCqQFPxSyvKbaacAsjhbystCN86nRtW4xhR3PMLr7zsrx2qgsY/BwKl/gch4jdPSvXCByZmf450nFSXQf6MpPUKetp54QwOcJj51veB2Um1PMKTJmVcUClKblWZp4kMf9drGO6CzicRYZxdZK2Dy/bXcyp+V/kRYe9AkbUNRg1zd8j+AtqYz+bIFpbN2QtxWtNfLE1qiPcSFXSadScyjpXAfjd/+opAXyCRYiXclV00KsLutlU8MMfvOo4VGOvdtyGwJRtyory+q1ZIfXyLoWJmgIDJkiOu7xF0vbO12xRefkDmx X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Tue, 27 Jun 2023, Jason Gunthorpe wrote: > On Wed, Jun 21, 2023 at 07:36:11PM -0700, Hugh Dickins wrote: > > [PATCH v3 05/12] powerpc: add pte_free_defer() for pgtables sharing page ... > Yes, this makes sense to me, very simple.. > > I always for get these details but atomic_dec_and_test() is a release? > So the SetPageActive is guarenteed to be visible in another thread > that reaches 0? Yes, that's my understanding - so the TestClearPageActive adds more to the guarantee than is actually needed. "release": you speak the modern language, whereas I haven't advanced from olden-days barriers: atomic_dec_and_test() meets atomic_t.txt's - RMW operations that have a return value are fully ordered; which a quick skim of present-day memory-barriers.txt suggests would imply both ACQUIRE and RELEASE. Please correct me if I'm mistaken! Hugh