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[2003:d8:2f1d:ed00:1769:dd7c:7208:eb33]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4562eb63551sm16517585e9.24.2025.07.16.03.44.24 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 16 Jul 2025 03:44:25 -0700 (PDT) Message-ID: Date: Wed, 16 Jul 2025 12:44:23 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v7 1/7] selftests/proc: add /proc/pid/maps tearing from vma split test To: Suren Baghdasaryan , akpm@linux-foundation.org Cc: Liam.Howlett@oracle.com, lorenzo.stoakes@oracle.com, vbabka@suse.cz, peterx@redhat.com, jannh@google.com, hannes@cmpxchg.org, mhocko@kernel.org, paulmck@kernel.org, shuah@kernel.org, adobriyan@gmail.com, brauner@kernel.org, josef@toxicpanda.com, yebin10@huawei.com, linux@weissschuh.net, willy@infradead.org, osalvador@suse.de, andrii@kernel.org, ryan.roberts@arm.com, christophe.leroy@csgroup.eu, tjmercier@google.com, kaleshsingh@google.com, aha310510@gmail.com, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kselftest@vger.kernel.org References: <20250716030557.1547501-1-surenb@google.com> <20250716030557.1547501-2-surenb@google.com> From: David Hildenbrand Autocrypt: addr=david@redhat.com; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Stat-Signature: dida6me56ondf51eynf19qto3mq388ba X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: 546A21C0005 X-Rspam-User: X-HE-Tag: 1752662669-900767 X-HE-Meta: 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 TMhkSrBl J5qDOVrCLic/qDNXshQoK4byFA0KfHcW+ZZpiap5zjJrlItPrQljWaTPguE8eBuGtKHg5FkzEx/H8toPLVs1mtZ5uFzl4+uEJRP1T8ss5I5fsWkJesN45Ohm+WmxrxFUUXrfoq5JZX9iAXAHCyqdrPYxTs5AzBE26PkxoUYpzSDp2naFt6qQdTSJF+FxhgO5qs+wq86dbsEZfO3Gej0aZY5PIPKbVDDyRpt3eN55WqaQ3T4gTCFql7ueJ0qVTCwYcrN8YwDBkaJFNAxonu8xbkBEnyva9e5fNfOQqHPvUWazQvHBa9qM+OBKzLSzj4AooPQBQFHKSPFOORPispmxSIFEPUfODx1i8wEUHkLaSvhGT5iv66srR3RM+keEWQgBxOFLA1mFqXVZuCyCyEOWweRw3+6iGkPMjY29Sd149ONdi7jOe/+1mY5ctjX6oZfY+2o7K6jZYJeIw4ytkAUyvE/nmLaqUPr8cjuF2/U/ySAIRtMo= 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: List-Subscribe: List-Unsubscribe: On 16.07.25 05:05, Suren Baghdasaryan wrote: > The /proc/pid/maps file is generated page by page, with the mmap_lock > released between pages. This can lead to inconsistent reads if the > underlying vmas are concurrently modified. For instance, if a vma split > or merge occurs at a page boundary while /proc/pid/maps is being read, > the same vma might be seen twice: once before and once after the change. > This duplication is considered acceptable for userspace handling. > However, observing a "hole" where a vma should be (e.g., due to a vma > being replaced and the space temporarily being empty) is unacceptable. > > Implement a test that: > 1. Forks a child process which continuously modifies its address space, > specifically targeting a vma at the boundary between two pages. > 2. The parent process repeatedly reads the child's /proc/pid/maps. > 3. The parent process checks the last vma of the first page and > the first vma of the second page for consistency, looking for the > effects of vma splits or merges. > > The test duration is configurable via the -d command-line parameter > in seconds to increase the likelihood of catching the race condition. > The default test duration is 5 seconds. > > Example Command: proc-maps-race -d 10 > > Signed-off-by: Suren Baghdasaryan Why is this selftest not making use of any kselftest framework? I'm sure there is a very good reason :) Reading assert() feels very weird compared to other selftests. -- Cheers, David / dhildenb