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[24.6.216.183]) by smtp.gmail.com with ESMTPSA id h13-20020a170902680d00b00174d9bbeda4sm1627756plk.197.2022.10.29.12.28.34 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Sat, 29 Oct 2022 12:28:35 -0700 (PDT) Content-Type: text/plain; charset=us-ascii Mime-Version: 1.0 (Mac OS X Mail 16.0 \(3696.120.41.1.1\)) Subject: Re: [PATCH 01/13] mm: Update ptep_get_lockless()s comment From: Nadav Amit In-Reply-To: Date: Sat, 29 Oct 2022 12:28:33 -0700 Cc: Peter Zijlstra , Jann Horn , John Hubbard , X86 ML , Matthew Wilcox , Andrew Morton , kernel list , Linux-MM , Andrea Arcangeli , "Kirill A . Shutemov" , jroedel@suse.de, ubizjak@gmail.com, Alistair Popple Content-Transfer-Encoding: quoted-printable Message-Id: References: <20221022111403.531902164@infradead.org> <20221022114424.515572025@infradead.org> <2c800ed1-d17a-def4-39e1-09281ee78d05@nvidia.com> <6C548A9A-3AF3-4EC1-B1E5-47A7FFBEB761@gmail.com> <47678198-C502-47E1-B7C8-8A12352CDA95@gmail.com> To: Linus Torvalds X-Mailer: Apple Mail (2.3696.120.41.1.1) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Oct 29, 2022, at 12:14 PM, Linus Torvalds = wrote: > On Sat, Oct 29, 2022 at 11:58 AM Linus Torvalds > wrote: >> Still not tested in any way, shape, or form. I decided I wanted to >> send this one before booting into this and possibly blowing up ;^) >=20 > Well, it boots, and I see no difference with your PoC code. >=20 > It didn't fail for me before, it doesn't fail for me with those = patches. >=20 > Again, the "it doesn't fail for me" is probably because I'm running it > incorrectly, although for all I know there can also be hardware > differences. Please give me some time to test it. I presume you ran it with block ram device (not tmpfs) and not on a virtual machine (which can affect = besides Intel/AMD implementation differences). But even if your patches work and the tests pass, I am not sure it means that everything is fine. I did not try to trigger a race with shrink_page_list(), and doing that might be harder than the race I tried = to create before. I need to do some tracing to understand what I was = missing in my understanding of the shrink_page_list() - assuming that I am mistaken about the buffers being potentially released. I would note that my concern about releasing the buffers is partially = driven by to issues that were reported before [1]. I am actually not sure how = they were resolved. [1] https://lore.kernel.org/all/20180103100430.GE4911@quack2.suse.cz/