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Howlett" , Vlastimil Babka , Mike Rapoport , Michal Hocko , Shakeel Butt , Jann Horn , linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-rt-devel@lists.linux.dev, Peter Zijlstra , Ingo Molnar , Will Deacon , Boqun Feng , Waiman Long , Sebastian Andrzej Siewior , Clark Williams , Steven Rostedt Subject: Re: [PATCH v3 06/10] mm/vma: clean up __vma_enter/exit_locked() Message-Id: <20260122125529.1f4a1806fd918155e0a5824b@linux-foundation.org> In-Reply-To: References: X-Mailer: Sylpheed 3.7.0 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam12 X-Stat-Signature: 383f93ooey9r4km9aex356f59cu3bwfb X-Rspamd-Queue-Id: AD8EDA000A X-Rspam-User: X-HE-Tag: 1769115326-352234 X-HE-Meta: U2FsdGVkX19/RCDj8RW5OtVS1kkfcOqjJMftANahmug14cYdWkimtiKm4uPWYhpnk3hRnmUxUUH1A8w6tq8bvxcIXefBD8ZWTE8TBSaWJrZTit/BjN1zLT61AQ8IOm61xKomhS3Mlj5GyPw9fHLq9s6EAVR5qb9cSgC9pdQo20lYCDQb7PiGOTgiaveVOpF/O/eRCXoiZH3wnk3ttWo48tFf7MEhCRmahtqHJDGCSDP7zuT7iyXLlGFrQu4Zc70BlQoFvVJohbgQMmNpBJdQv1AydCstkSyQEd3E3FaQHMe9klxmROT+Q9P1hZ6qp1NOb5ugD9XN6nxuRujEUf2kVFKtThwaIZpEsg7FDdqOoNGRv0tw+eqYenj0yqhqFVw458ntr/LMQ3JPio2nbyAEougavvNOSsEH2sxHgNncI7D4OGKvQrH8BNTIeWIV5UDaUYzxcO7SQtI7Ched0yv9trQkiHfb4bjY5rII9W4rbOhT0lqCf6T3DiqNopu+sl2sCKRy+SXMAVFRjs6xhavaskwKckFDDhM+M6hQGk1QZpz8XSyL02HQb0ck9SpofwyLu62XSDkEoU6kL258yz77wDbyaV0uhEwpCG2UvYkS+im+z+cv/fjeHJFKZSahUf48NQO+5k9kV7XlNlQAi51YeFoQcBztwawkR61IZQ1Kg9B4WY64/HyfSaLl3QZYrijGlJzlU+qCVZNSYqURFkN4o27Hngl1Gai0puhaPUGxkqeEwNy+caOeMyfyJNK4ZLb4f7QdFOizXI8hWESbZBLMX4DiU7TdEvn2fcz8FGkAYrTtJiplZxQ8ZlDL+PY8bspSQiZGPjG6kTdp3uOHBcQaNgtyuGGldl3uVyE3ZYTCj+3RXiBJUkrIekwlZq5g4Wnum265ggP91fk7fh/BUfI7Jl8djn4XqSkiV8cNOk+8TR20/hzw8p3lG0rQBF2ouU6MbmoYGdKBj/FoOS/uQ+8 Yzcqnpf2 0SSrcjxfciUaIrvgcewKT5R88rcsL1yCF1k1vq2IL5R/JRw0LYizJPCcx3SS2cJEAXvIrjA6zo2Upo2GGtg8unGq0dw9ma5Fj2ncodJ4+LaLEg2CsVkUX0ak5ITP8OX8A1N/R1K/AmXOG3yUb5EUBumR2utGwjpuW2BzRh6giA5lrQ48o+PERo8kIZktjVEcgexfPuxHGjdxheKt2rzMG3DWtXFmuzf2ZZuNCro82ozC9+Issg4St74vG5R/fG4Awjzy3yy0oFzhat5a4lzrLE1rDArc8MWZwM9r4pnk+VoalrNoJN9Y8zITKm95GmRXa7M1GDlw0BzULqFKi28nqV8YL3WZ7wCISMhZ7Ln3rZgMiYXAxMYq4v9FR1XRYqamca697e/DOpNPcVNI= 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 Thu, 22 Jan 2026 12:15:20 -0800 Suren Baghdasaryan wrote: > > + /* vma should remain attached. */ > > + if (locked) > > + WARN_ON_ONCE(__vma_exit_exclusive_locked(vma)); > > I'm wary of calling functions from WARN_ON_ONCE() statements. If > someone decides to replace WARN_ON_ONCE() with VM_WARN_ON_ONCE(), the > call will disappear when CONFIG_DEBUG_VM=n. Maybe I'm being paranoid > but it's because I have been bitten by that before... Yes please. The elision is desirable if the function has no side-effects, but __vma_exit_exclusive_locked() changes stuff. Someone(tm) should check for this. A pathetically partial grep turns up plenty of things: mm/slab_common.c: if (head && !WARN_ON_ONCE(!poll_state_synchronize_rcu_full(&head_gp_snap))) mm/slab_common.c: if (!WARN_ON_ONCE(!poll_state_synchronize_rcu_full(&bnode->gp_snap))) { mm/page-writeback.c: WARN_ON_ONCE(atomic_long_add_return(delta, mm/page_isolation.c: WARN_ON_ONCE(!pageblock_unisolate_and_move_free_pages(zone, page)); mm/page_alloc.c: VM_WARN_ONCE(get_pageblock_isolate(page), mm/numa_memblks.c: WARN_ON(memblock_clear_hotplug(0, max_addr)); mm/numa_memblks.c: WARN_ON(memblock_set_node(0, max_addr, &memblock.memory, NUMA_NO_NODE)); mm/numa_memblks.c: WARN_ON(memblock_set_node(0, max_addr, &memblock.reserved, mm/zsmalloc.c: WARN_ON(!zpdesc_trylock(zpdesc));