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[87.161.167.7]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-442f33804d9sm200084815e9.12.2025.05.19.00.36.57 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 19 May 2025 00:36:57 -0700 (PDT) Message-ID: <14bbdbd4-fa86-4317-a051-8e1defc7192e@redhat.com> Date: Mon, 19 May 2025 09:36:55 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [BUG] RCU Detected Stall in sys_process_vm_writev To: Guoyu Yin , akpm@linux-foundation.org Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, dave.hansen@linux.intel.com, luto@kernel.org, peterz@infradead.org, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, x86@kernel.org, hpa@zytor.com References: 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: X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: X_1QXvJPD0dg9sCnfiePmYbIM1v5LUwYg5U_IaD8hjc_1747640219 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Stat-Signature: c3jwymgkm8ykewop5ghqubqp66y1814u X-Rspam-User: X-Rspamd-Queue-Id: 7FC3118000C X-Rspamd-Server: rspam06 X-HE-Tag: 1747640222-308144 X-HE-Meta: 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 chJf4j/D jHKcjdUVKsjKQTq5z+/O6ayR6lmxq6S+U20zqXZlBHia5vB0vr4bD2qXoqdj+waihPkYgiHEp49v4fd2vCDtjjJmiNa+sJXU0RjfQ+tMS/ru+dzjgcNq749TiKvs/YlOd7b16fOSt6047VVJEoYArNNoxOr/r7srq1plSWG5UbwYe/MqBvIlqT4VKYGLnU1kewW3VAVMsAmksWoNdoqRyFLZ+MpJJgZYxnbrqtQmFDRUmxqMSwav4kmYpvuOPSjTPYURlCjUGu189KlN34qkjpsKtw5Ji6SbaPpEQQZZiR3Egs7DduXvYzMsQM2cFyyUquFPADFldEduccyRkCsHSXn+DCvC3LIaDdO0AGXG8TZMemZQl4Hu/oF0zuPLbj3pchlERLqZTXwSp5OjWPcRS+Qy3ZmmY2/d+8HZIEHh2JY16iabYeJ+UvSw156IVPt/BpuHGY7A0jGHyonK3pBfcEJOiMw== 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 19.05.25 07:19, Guoyu Yin wrote: > Hi, > > I discovered a kernel crash using the Syzkaller framework, described > as "INFO: rcu detected stall in sys_process_vm_writev". This issue > occurs during the execution of the sys_process_vm_writev system call, > where RCU detects a stall on CPU 0. > > From the dmesg log, CPU 3 is stuck trying to acquire a spinlock in the > pgd_free function (arch/x86/mm/pgtable.c:490), leading to the RCU > stall. This is likely caused by spinlock contention triggered by the > page pinning and unpinning logic in sys_process_vm_writev under high > load or abnormal conditions. pgd_free() calls pgd_dtor() where we should be taking the pgd_lock. Apart from that, only the buddy allocator might be taking locks when freeing the page. > > I recommend reviewing the page pinning (pin_user_pages_remote) and > unpinning (unpin_user_pages_dirty_lock) logic in > process_vm_rw_single_vec (mm/process_vm_access.c) to ensure it does > not cause prolonged spinlock blocking due to scheduling delays or > resource contention. This almost reads like AI generated content. Anyhow, unpin_user_pages_dirty_lock() should only be taking the folio lock, and pin_user_pages_remote() should only be taking page table locks. As I am sure you wouldn't bother us with AI generated slop, what makes you think that the pgd_lock is relevant in the context of GUP? -- Cheers, David / dhildenb