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[24.6.216.183]) by smtp.gmail.com with ESMTPSA id dw13-20020a17090b094d00b00226f49eca92sm1840043pjb.28.2023.01.18.14.22.18 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Wed, 18 Jan 2023 14:22:18 -0800 (PST) Content-Type: text/plain; charset=utf-8 Mime-Version: 1.0 (Mac OS X Mail 16.0 \(3731.300.101.1.3\)) Subject: Re: [PATCH v6 3/5] lazy tlb: shoot lazies, non-refcounting lazy tlb mm reference handling scheme From: Nadav Amit In-Reply-To: <20230118080011.2258375-4-npiggin@gmail.com> Date: Wed, 18 Jan 2023 14:22:07 -0800 Cc: Andrew Morton , Andy Lutomirski , Linus Torvalds , linux-arch , linux-mm , linuxppc-dev@lists.ozlabs.org Content-Transfer-Encoding: quoted-printable Message-Id: <5F3590B8-3F25-4EFB-BE3A-D32AAAC0B2F4@gmail.com> References: <20230118080011.2258375-1-npiggin@gmail.com> <20230118080011.2258375-4-npiggin@gmail.com> To: Nicholas Piggin X-Mailer: Apple Mail (2.3731.300.101.1.3) X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: BB7201C001A X-Rspam-User: X-Stat-Signature: mg359tmutbb47nrfmiq4so58a55inppx X-HE-Tag: 1674080540-776812 X-HE-Meta: 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 G1XYF42k AGGfIbNcIod+M2xy5BpsD2xTcGtnBraVFVg6Cmqnpa0KafirQKo5nBgpyyYHcKML0YzwpmalbQJGuvblB5wQ8AK9eo9QcVeWGejl+YFQ48LGnTVg/Eh385/vu5Qt8GXnL80v7OIQQ1EnHyfYe3CzyPVgMjA== 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 Jan 18, 2023, at 12:00 AM, Nicholas Piggin = wrote: >=20 > +static void do_shoot_lazy_tlb(void *arg) > +{ > + struct mm_struct *mm =3D arg; > + > + if (current->active_mm =3D=3D mm) { > + WARN_ON_ONCE(current->mm); > + current->active_mm =3D &init_mm; > + switch_mm(mm, &init_mm, current); > + } > +} I might be out of touch - doesn=E2=80=99t a flush already take place = when we free the page-tables, at least on common cases on x86? IIUC exit_mmap() would free page-tables, and whenever page-tables are freed, on x86, we do shootdown regardless to whether the target CPU TLB = state marks is_lazy. Then, flush_tlb_func() should call switch_mm_irqs_off() = and everything should be fine, no? [ I understand you care about powerpc, just wondering on the effect on = x86 ]