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b=UJaB6/R7uk1mlmkAIzYMEc7DUTnLcT8xULUIpx66y+1F/KK6ZNgvK+sbbeRDlU0yS ulN/zOlwsrFR53cUj7rj/bJ+Vq7YZe1Sf18FOuGYthYqNZZvmCD9Epe1JVyBVuXPFE ghqt34gN5SdUWf0sYcfx6GtBeb2oiKClfvHGkRr0yAI4L5jkMNKpSDo5lRyTdQoD9N bscu3+1RVSih/32Knb+bUHkgwgQAshk/mnTLhjZ7PcxYaX+twfLad4pcz26uPb1rpY OrODKE69jW3mWAszw1sQtuG7tAJLqb9XlAIxziF6jTuNJw6Yf/tYL0k0JB70TTZas4 yQEQsZ0xeL/0w== Message-ID: <76579248-64db-47bf-b8d0-4eb3ca556f5a@kernel.org> Date: Sat, 31 Oct 2026 11:52:30 +0100 X-Archived-By: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm/migrate: fix softlockup in do_pages_stat() with huge page arrays To: Qi Xi , Andrew Morton , linux-mm@kvack.org Cc: Zi Yan , Matthew Brost , Joshua Hahn , Byungchul Park , Gregory Price , Ying Huang , Alistair Popple , Qiliang Yuan , linux-kernel@vger.kernel.org, wangkefeng.wang@huawei.com, sunnanyong@huawei.com, xiqi2@huawei.com References: <20261031033330.3416326-1-xiqi5703@163.com> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 604CBC0003 X-Stat-Signature: xugdwzea4uftp5jf673gybpswkqbt3rx X-Rspam-User: X-Spam-Status: No, score=-17.3 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_PASS, SPF_PASS,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=4.0.1 X-HE-Tag: 1793443958-814129 X-HE-Meta: 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 oEDHKHYd 8tzUB9fBTiDBWzobnCPvvWJxr4ui1LkEGvjdabOTDhf1qkqteITlzyDDbDY/vVEqGLtM0RobhHSqpFsmiwCTg3EEbIWKuO1HdRvDYwmlUCtW6SmIiYEl1oO0tFUIZYqXo4IMOzOMYhiFm+nYes0B679W6rueA7bEO5V/m0g675D6CZWFq3Fkn6rxg7/vQ0d4MzOQUnRKrkNGGJr+cPQljAQYbpy8TFR9cKueuj9xe0ltSbDhpqzlDC7qz6UfDyExHQQBj3ij2t8p/+ojlquuvNe3NBUIw0htipgSaRp+vkJyc9bL8X5wp3CiB60BqzdM6aJFCiBRQX5Qcw4TJo479fu8i4XD6UGmn4ZVvxNPrkjZBAeR+WkOPZGtAgmGcvAulYzTT2JQ9Z/OzJfSAPBkir+HziA== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 On 10/31/26 04:33, Qi Xi wrote: > From: Qi Xi > > do_pages_stat() walks the user page array in 16-page chunks but never > reschedules, so a huge nr_pages can hold a CPU past the watchdog > threshold on non-preemptible kernels. Add cond_resched() to the loop so > long move_pages() node-query calls yield periodically. > > With KASAN and function tracing enabled, a move_pages() node query > (nodes == NULL) over 10 million page entries (~40GB) can trigger the > softlockup on a PREEMPT_NONE kernel. > > Fixes: 80bba1290ab5 ("mm: no get_user/put_user while holding mmap_sem in do_pages_stat?") > Signed-off-by: Qi Xi > --- > mm/migrate.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/mm/migrate.c b/mm/migrate.c > index 7bdcdb57652f..6c2371020cc5 100644 > --- a/mm/migrate.c > +++ b/mm/migrate.c > @@ -2545,6 +2545,7 @@ static int do_pages_stat(struct mm_struct *mm, unsigned long nr_pages, > > chunk_offset += chunk_nr; > nr_pages -= chunk_nr; > + cond_resched(); > } > return nr_pages ? -EFAULT : 0; > } I though we wanted to stop throwing in cond_resched() at this point? -- Cheers, David