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[PATCH v2] mm/migrate: fix softlockup in do_pages_move() with huge page arrays Cc: , , , , , , , , To: , , From: "Zi Yan" X-Mailer: aerc 0.22.0 References: <20261108142831046W_fbNCAFfuY0BjHPCCHgi@zte.com.cn> In-Reply-To: <20261108142831046W_fbNCAFfuY0BjHPCCHgi@zte.com.cn> X-ClientProxiedBy: CH5PR03CA0022.namprd03.prod.outlook.com (2603:10b6:610:1f1::8) To IA0PR12MB8374.namprd12.prod.outlook.com (2603:10b6:208:40e::7) X-Archived-By: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: IA0PR12MB8374:EE_|SACPR12MB439974:EE_ X-MS-Office365-Filtering-Correlation-Id: b1ba37e1-49e7-4fd2-998f-08df3ed5d3f0 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|23010399003|366016|376014|7416014|1800799024|18002099003|22082099003|6133799003|11063799006|56012099006|10067099003|261102123227099003|261022105027099003|261022075727099003|261021121427099003|261026140227099003|261009223027099003|261028144727099003|261026121527099003; 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 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 Sun Nov 8, 2026 at 1:28 AM EST, wrote: > From: Shao Mingyin > > mm/migrate: fix softlockup in do_pages_move() with huge page arrays > > do_pages_move() walks the array one page at a time. An entry naming the > node its page is already on is never queued, so the loop runs without a > voluntary preemption point on a non-preemptible kernel; the existing > cond_resched() calls in the migration code are only reached after a > folio has been queued. nr_pages comes straight from the syscall. > > A 6.6.60 x86_64 kernel with CONFIG_PREEMPT_NONE=3Dy and CONFIG_NUMA=3Dy > reproduces this under QEMU TCG: 50 million entries pointing at a page > already on the target node keep the CPU in do_pages_move() for 42.9 s and > trip the softlockup watchdog; with this patch the same call completes in > 44.3 s without a softlockup. > > Add cond_resched() so that long calls yield periodically. > do_pages_stat() had the same problem; it was fixed by 8e934ab44389. In > current mainline only alpha, hexagon and classic m68k can select > PREEMPT_NONE and they cannot enable CONFIG_NUMA, so this mainly targets > pre-v7.0 stable kernels. > > Fixes: a49bd4d71637 ("mm, numa: rework do_pages_move") > Cc: stable@vger.kernel.org > Signed-off-by: Shao Mingyin > --- > Changes in v2: > - describe the reproduction and the code path, as requested by David > Hildenbrand; no code change > - correct the do_pages_stat() reference (fixed by 8e934ab44389) > Link: https://lore.kernel.org/all/20261107213856462Jx8pIdgdtLvPLfOFTwV4X@= zte.com.cn/ > > mm/migrate.c | 2 ++ > 1 file changed, 2 insertions(+) > Acked-by: Zi Yan --=20 Best Regards, Yan, Zi