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[2003:d8:2f18:7500:202e:b0f1:76d6:f9af]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4538233c1easm192021175e9.3.2025.07.01.04.53.32 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 01 Jul 2025 04:53:32 -0700 (PDT) Message-ID: <132ac071-01ab-4d4d-bc6d-208413410bc2@redhat.com> Date: Tue, 1 Jul 2025 13:53:31 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 0/2] mm/memory_hotplug: fixup crash during uevent handling To: Hannes Reinecke Cc: Oscar Salvador , linux-mm@kvack.org, Hannes Reinecke References: <20250701114155.16452-1-hare@kernel.org> 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/g1oFAl8Ox4kFCRKpKXgACgkQTd4Q 9wD/g1oHcA//a6Tj7SBNjFNM1iNhWUo1lxAja0lpSodSnB2g4FCZ4R61SBR4l/psBL73xktp rDHrx4aSpwkRP6Epu6mLvhlfjmkRG4OynJ5HG1gfv7RJJfnUdUM1z5kdS8JBrOhMJS2c/gPf wv1TGRq2XdMPnfY2o0CxRqpcLkx4vBODvJGl2mQyJF/gPepdDfcT8/PY9BJ7FL6Hrq1gnAo4 3Iv9qV0JiT2wmZciNyYQhmA1V6dyTRiQ4YAc31zOo2IM+xisPzeSHgw3ONY/XhYvfZ9r7W1l pNQdc2G+o4Di9NPFHQQhDw3YTRR1opJaTlRDzxYxzU6ZnUUBghxt9cwUWTpfCktkMZiPSDGd KgQBjnweV2jw9UOTxjb4LXqDjmSNkjDdQUOU69jGMUXgihvo4zhYcMX8F5gWdRtMR7DzW/YE BgVcyxNkMIXoY1aYj6npHYiNQesQlqjU6azjbH70/SXKM5tNRplgW8TNprMDuntdvV9wNkFs 9TyM02V5aWxFfI42+aivc4KEw69SE9KXwC7FSf5wXzuTot97N9Phj/Z3+jx443jo2NR34XgF 89cct7wJMjOF7bBefo0fPPZQuIma0Zym71cP61OP/i11ahNye6HGKfxGCOcs5wW9kRQEk8P9 M/k2wt3mt/fCQnuP/mWutNPt95w9wSsUyATLmtNrwccz63XOwU0EVcufkQEQAOfX3n0g0fZz 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+DWgUCXw7HsgUJEqkpoQAKCRBN3hD3AP+DWrrpD/4qS3dyVRxDcDHIlmguXjC1Q5tZTwNB boaBTPHSy/Nksu0eY7x6HfQJ3xajVH32Ms6t1trDQmPx2iP5+7iDsb7OKAb5eOS8h+BEBDeq 3ecsQDv0fFJOA9ag5O3LLNk+3x3q7e0uo06XMaY7UHS341ozXUUI7wC7iKfoUTv03iO9El5f XpNMx/YrIMduZ2+nd9Di7o5+KIwlb2mAB9sTNHdMrXesX8eBL6T9b+MZJk+mZuPxKNVfEQMQ a5SxUEADIPQTPNvBewdeI80yeOCrN+Zzwy/Mrx9EPeu59Y5vSJOx/z6OUImD/GhX7Xvkt3kq Er5KTrJz3++B6SH9pum9PuoE/k+nntJkNMmQpR4MCBaV/J9gIOPGodDKnjdng+mXliF3Ptu6 3oxc2RCyGzTlxyMwuc2U5Q7KtUNTdDe8T0uE+9b8BLMVQDDfJjqY0VVqSUwImzTDLX9S4g/8 kC4HRcclk8hpyhY2jKGluZO0awwTIMgVEzmTyBphDg/Gx7dZU1Xf8HFuE+UZ5UDHDTnwgv7E th6RC9+WrhDNspZ9fJjKWRbveQgUFCpe1sa77LAw+XFrKmBHXp9ZVIe90RMe2tRL06BGiRZr jPrnvUsUUsjRoRNJjKKA/REq+sAnhkNPPZ/NNMjaZ5b8Tovi8C0tmxiCHaQYqj7G2rgnT0kt WNyWQQ== Organization: Red Hat In-Reply-To: <20250701114155.16452-1-hare@kernel.org> X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: Iu0jKq9qtrSZcArcRtIYwZMhEyJ0UnAkiWIzcJ8h9ms_1751370814 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 99653140006 X-Stat-Signature: uderzqxqb7yjmnid5a7qsggo8bbd5aj3 X-Rspam-User: X-HE-Tag: 1751370816-765438 X-HE-Meta: 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 2nMDt0HZ oHRq9PDeNUr3AMFqhybqTrplG4aEofMVtfoEozbeBYouctgDhNDuQcNl6+tiw/MXO2U+Wy+HxqvlPoF2nKnJUjjQanqIT0MgoHinRIC1DWWogNbLn2yKzNMqQZg== 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 01.07.25 13:41, Hannes Reinecke wrote: > From: Hannes Reinecke > > Hi all, Hi, > > 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 ... Probably just they way things developed historically. We have some weird things to handle when we have early memory blocks that span multiple nodes. memory_block_add_nid() is all about that, and maintaining mem->zone accordingly. Probably should just be cleaned up. -- Cheers, David / dhildenb