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[149.14.88.26]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-45895375163sm19361165e9.9.2025.07.30.02.39.15 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 30 Jul 2025 02:39:15 -0700 (PDT) Message-ID: Date: Wed, 30 Jul 2025 11:39:15 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCHv4 0/3] mm/memory_hotplug: fixup crash during uevent handling To: Hannes Reinecke , Andrew Morton , Hannes Reinecke Cc: Oscar Salvador , linux-mm@kvack.org References: <20250729064637.51662-1-hare@kernel.org> <20250729133806.979475704b1162d7aea99b2b@linux-foundation.org> <907ee759-6051-4d47-bf09-cea362ac0cd9@suse.de> From: David Hildenbrand Autocrypt: addr=david@redhat.com; keydata= xsFNBFXLn5EBEAC+zYvAFJxCBY9Tr1xZgcESmxVNI/0ffzE/ZQOiHJl6mGkmA1R7/uUpiCjJ dBrn+lhhOYjjNefFQou6478faXE6o2AhmebqT4KiQoUQFV4R7y1KMEKoSyy8hQaK1umALTdL QZLQMzNE74ap+GDK0wnacPQFpcG1AE9RMq3aeErY5tujekBS32jfC/7AnH7I0v1v1TbbK3Gp XNeiN4QroO+5qaSr0ID2sz5jtBLRb15RMre27E1ImpaIv2Jw8NJgW0k/D1RyKCwaTsgRdwuK Kx/Y91XuSBdz0uOyU/S8kM1+ag0wvsGlpBVxRR/xw/E8M7TEwuCZQArqqTCmkG6HGcXFT0V9 PXFNNgV5jXMQRwU0O/ztJIQqsE5LsUomE//bLwzj9IVsaQpKDqW6TAPjcdBDPLHvriq7kGjt WhVhdl0qEYB8lkBEU7V2Yb+SYhmhpDrti9Fq1EsmhiHSkxJcGREoMK/63r9WLZYI3+4W2rAc UucZa4OT27U5ZISjNg3Ev0rxU5UH2/pT4wJCfxwocmqaRr6UYmrtZmND89X0KigoFD/XSeVv jwBRNjPAubK9/k5NoRrYqztM9W6sJqrH8+UWZ1Idd/DdmogJh0gNC0+N42Za9yBRURfIdKSb B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzSREYXZpZCBIaWxk ZW5icmFuZCA8ZGF2aWRAcmVkaGF0LmNvbT7CwZgEEwEIAEICGwMGCwkIBwMCBhUIAgkKCwQW AgMBAh4BAheAAhkBFiEEG9nKrXNcTDpGDfzKTd4Q9wD/g1oFAmgsLPQFCRvGjuMACgkQTd4Q 9wD/g1o0bxAAqYC7gTyGj5rZwvy1VesF6YoQncH0yI79lvXUYOX+Nngko4v4dTlOQvrd/vhb 02e9FtpA1CxgwdgIPFKIuXvdSyXAp0xXuIuRPQYbgNriQFkaBlHe9mSf8O09J3SCVa/5ezKM OLW/OONSV/Fr2VI1wxAYj3/Rb+U6rpzqIQ3Uh/5Rjmla6pTl7Z9/o1zKlVOX1SxVGSrlXhqt kwdbjdj/csSzoAbUF/duDuhyEl11/xStm/lBMzVuf3ZhV5SSgLAflLBo4l6mR5RolpPv5wad GpYS/hm7HsmEA0PBAPNb5DvZQ7vNaX23FlgylSXyv72UVsObHsu6pT4sfoxvJ5nJxvzGi69U s1uryvlAfS6E+D5ULrV35taTwSpcBAh0/RqRbV0mTc57vvAoXofBDcs3Z30IReFS34QSpjvl Hxbe7itHGuuhEVM1qmq2U72ezOQ7MzADbwCtn+yGeISQqeFn9QMAZVAkXsc9Wp0SW/WQKb76 FkSRalBZcc2vXM0VqhFVzTb6iNqYXqVKyuPKwhBunhTt6XnIfhpRgqveCPNIasSX05VQR6/a OBHZX3seTikp7A1z9iZIsdtJxB88dGkpeMj6qJ5RLzUsPUVPodEcz1B5aTEbYK6428H8MeLq NFPwmknOlDzQNC6RND8Ez7YEhzqvw7263MojcmmPcLelYbfOwU0EVcufkQEQAOfX3n0g0fZz Bgm/S2zF/kxQKCEKP8ID+Vz8sy2GpDvveBq4H2Y34XWsT1zLJdvqPI4af4ZSMxuerWjXbVWb T6d4odQIG0fKx4F8NccDqbgHeZRNajXeeJ3R7gAzvWvQNLz4piHrO/B4tf8svmRBL0ZB5P5A 2uhdwLU3NZuK22zpNn4is87BPWF8HhY0L5fafgDMOqnf4guJVJPYNPhUFzXUbPqOKOkL8ojk CXxkOFHAbjstSK5Ca3fKquY3rdX3DNo+EL7FvAiw1mUtS+5GeYE+RMnDCsVFm/C7kY8c2d0G NWkB9pJM5+mnIoFNxy7YBcldYATVeOHoY4LyaUWNnAvFYWp08dHWfZo9WCiJMuTfgtH9tc75 7QanMVdPt6fDK8UUXIBLQ2TWr/sQKE9xtFuEmoQGlE1l6bGaDnnMLcYu+Asp3kDT0w4zYGsx 5r6XQVRH4+5N6eHZiaeYtFOujp5n+pjBaQK7wUUjDilPQ5QMzIuCL4YjVoylWiBNknvQWBXS lQCWmavOT9sttGQXdPCC5ynI+1ymZC1ORZKANLnRAb0NH/UCzcsstw2TAkFnMEbo9Zu9w7Kv AxBQXWeXhJI9XQssfrf4Gusdqx8nPEpfOqCtbbwJMATbHyqLt7/oz/5deGuwxgb65pWIzufa N7eop7uh+6bezi+rugUI+w6DABEBAAHCwXwEGAEIACYCGwwWIQQb2cqtc1xMOkYN/MpN3hD3 AP+DWgUCaCwtJQUJG8aPFAAKCRBN3hD3AP+DWlDnD/4k2TW+HyOOOePVm23F5HOhNNd7nNv3 Vq2cLcW1DteHUdxMO0X+zqrKDHI5hgnE/E2QH9jyV8mB8l/ndElobciaJcbl1cM43vVzPIWn 01vW62oxUNtEvzLLxGLPTrnMxWdZgxr7ACCWKUnMGE2E8eca0cT2pnIJoQRz242xqe/nYxBB /BAK+dsxHIfcQzl88G83oaO7vb7s/cWMYRKOg+WIgp0MJ8DO2IU5JmUtyJB+V3YzzM4cMic3 bNn8nHjTWw/9+QQ5vg3TXHZ5XMu9mtfw2La3bHJ6AybL0DvEkdGxk6YHqJVEukciLMWDWqQQ RtbBhqcprgUxipNvdn9KwNpGciM+hNtM9kf9gt0fjv79l/FiSw6KbCPX9b636GzgNy0Ev2UV m00EtcpRXXMlEpbP4V947ufWVK2Mz7RFUfU4+ETDd1scMQDHzrXItryHLZWhopPI4Z+ps0rB CQHfSpl+wG4XbJJu1D8/Ww3FsO42TMFrNr2/cmqwuUZ0a0uxrpkNYrsGjkEu7a+9MheyTzcm vyU2knz5/stkTN2LKz5REqOe24oRnypjpAfaoxRYXs+F8wml519InWlwCra49IUSxD1hXPxO WBe5lqcozu9LpNDH/brVSzHCSb7vjNGvvSVESDuoiHK8gNlf0v+epy5WYd7CGAgODPvDShGN g3eXuA== Organization: Red Hat In-Reply-To: <907ee759-6051-4d47-bf09-cea362ac0cd9@suse.de> X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: xPPKU5zfJqoCPV54AxDocszRtxYDZHyGb4OurmLCCEA_1753868357 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 5FD68C0002 X-Stat-Signature: nk6oj3am6hrdbjyttept1hbfepayyzhy X-Rspam-User: X-Rspamd-Server: rspam07 X-HE-Tag: 1753868360-521234 X-HE-Meta: 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 Ha/GwDi8 0v4eCudchq/zom6oun1Kby2aEOk1gG/C0DXy5gnwFg2UhKu5I4GhVrgXTaOHmEgVWJ8sc9148PNKJoW/i74lL/gH1zuEUHCICPvyvAy6929k4INumXwQe6j808EbmSElgnr5CGtjahHooU/Z9AzK+Ga+aEdZ3bHAa86bWaUBW5BQal5NP1rgwxofqU57j//EuoYVwDEpsytFTHzV5EFf/2VLKHdHgC1vbT/Izs8XDz0Uzh/v36oCcMHMBJOoPi1MkcizpM0iySsOF7aMupyZJ4PXFhzZEWau9Da6LxlsnyiM7rCbASwasV8zxyQEH2en57/k/27IEh6d7aZGfFQoYGlINO1pEvsf9TFdBnlLIjSe/RyVbaBjQ4metpU2LFsDuaoe9zV/g0FfvalQz3mfVWXAPN0l8Ck6Iovb7J2r91SXwQ3+q2vTTLYabyBJDROwZnA9KG7AwOd8Ptcnv/hdLOyfcPWBDRAwWRvq4wQA9/VV+xtA= 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 30.07.25 07:49, Hannes Reinecke wrote: > On 7/29/25 22:38, Andrew Morton wrote: >> On Tue, 29 Jul 2025 08:46:33 +0200 Hannes Reinecke wrote: >> >>> we have some udev rules trying to read the sysfs attribute 'valid_zones' during >>> an memory 'add' event, causing a crash in zone_for_pfn_range(). Debugging found >>> that mem->nid was set to NUMA_NO_NODE, which crashed in NODE_DATA(nid). >>> Further analysis revealed that we're running into a race with udev event >>> processing: add_memory_resource() has this function calls: >>> >>> 1) __try_online_node() >>> 2) arch_add_memory() >>> 3) create_memory_block_devices() >>> -> calls device_register() -> memory 'add' event >>> 4) node_set_online()/__register_one_node() >>> -> calls device_register() -> node 'add' event >>> 5) register_memory_blocks_under_node() >>> -> sets mem->nid >>> >>> Which, to the uninitated, is ... weird ... >>> >>> Why do we try to online the node in 1), but only register >>> the node in 4) _after_ we have created the memory blocks in 3) ? >>> And why do we set the 'nid' value in 5), when the uevent >>> (which might need to see the correct 'nid' value) is sent out >>> in 3) ? >>> There must be a reason, I'm sure ... >>> >>> So here's a small patchset to fixup uevent ordering. >> >> You know what I'm going to say :) >> >> Should we backport this into earlier kernels? Seeing "crash" make me >> think yes. >> >> But only one patch has a Fixes: target, and it's with the Fixes: tag >> that we tell -stable maintainers which kernel version(s) we want >> patched. >> >> So, still assuming "yes": is it possible to redo all this as a simple >> minimal patch which is suitable for backporting? And then a separate >> cleanup/refactoring series for future kernels? [3/3] doesn't seem to >> be needed in earlier kernels? >> >> IOW, if we wish to fix this crash in earlier kernels, I really cant use >> this series as presented. For now I'll add it to mm-new to get it a bit >> of exposure while we decide what to do. >> >> > And here's me who thought we were doing upstream work precisely to > _not_ having to do backports :-) > Oh well. > > I see if we can roll patch 1&2 into one; guess I'll need to do it > anyway for our kernel. I recall that for simple backports, it is possible to request cherry-picking related cleanups. Patch #1 is super simple. So I assume this can easily handled on the backport side as is (with a bit of manual work). If need be, patch #1 and #2 could be squashed I guess. -- Cheers, David / dhildenb