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[110.174.173.27]) by smtp.gmail.com with ESMTPSA id h15sm15368954pjc.14.2020.07.13.06.47.19 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 13 Jul 2020 06:47:20 -0700 (PDT) Date: Mon, 13 Jul 2020 23:47:14 +1000 From: Nicholas Piggin Subject: Re: [RFC PATCH 4/7] x86: use exit_lazy_tlb rather than membarrier_mm_sync_core_before_usermode To: Andy Lutomirski Cc: Anton Blanchard , Arnd Bergmann , linux-arch , LKML , Linux-MM , linuxppc-dev , Mathieu Desnoyers , Peter Zijlstra , X86 ML References: <20200710015646.2020871-1-npiggin@gmail.com> <20200710015646.2020871-5-npiggin@gmail.com> <1594613902.1wzayj0p15.astroid@bobo.none> In-Reply-To: <1594613902.1wzayj0p15.astroid@bobo.none> MIME-Version: 1.0 Message-Id: <1594647408.wmrazhwjzb.astroid@bobo.none> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable X-Rspamd-Queue-Id: 94CCD18086CBA X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam05 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: Excerpts from Nicholas Piggin's message of July 13, 2020 2:45 pm: > Excerpts from Andy Lutomirski's message of July 11, 2020 3:04 am: >> Also, as it stands, I can easily see in_irq() ceasing to promise to >> serialize. There are older kernels for which it does not promise to >> serialize. And I have plans to make it stop serializing in the >> nearish future. >=20 > You mean x86's return from interrupt? Sounds fun... you'll konw where to=20 > update the membarrier sync code, at least :) Oh, I should actually say Mathieu recently clarified a return from interrupt doesn't fundamentally need to serialize in order to support membarrier sync core. https://lists.ozlabs.org/pipermail/linuxppc-dev/2020-July/214171.html So you may not need to do anything more if you relaxed it. Thanks, Nick