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smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=C1sYa023; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 080F7606A326; Sat, 7 Nov 2026 18:20:13 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=C1sYa023 Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9B0C21F0089F; Sat, 7 Nov 2026 18:20:08 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794075612; bh=1pjnHje6Qb1kHlz8WaN4eNa2MT/clIj+haAeBAgYG+k=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=C1sYa023IOebqDzktccEL/GnqdyMhlnIn18DNUC1Sgtp9yv+XhSCgYpBawdgnNPGJ 1jmy08jxGm7xQR2DKYEEO9QPKbm2XQU3r1B6N5nBPd4HMWoU+CLSk9mGC3982NUaYj 0WEc5R8QPvn/ArI2m14ey2IbiN5/k/GUKWBYoD7IV96S6YDdd3ctTYzroOtVACDTPn kCLsaKsYERXgamn3Tv2at/jQX1x0iPX4Pp8A4dLYVt25eXkKVSqioBAPcwYkpQgKy4 PHJHTdaktocbt0gsWvH+P9L7jyt0OWP9th65AJD+QgiWizezgsGd0MHJDlQm91ilHr mScwirajJmJQQ== Message-ID: Date: Sat, 7 Nov 2026 19:20:03 +0100 X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm/migrate: fix softlockup in do_pages_move() with huge page arrays To: shao.mingyin@zte.com.cn, akpm@linux-foundation.org Cc: linux-mm@kvack.org, ziy@nvidia.com, matthew.brost@intel.com, joshua.hahnjy@gmail.com, byungchul@sk.com, gourry@gourry.net, ying.huang@linux.alibaba.com, apopple@nvidia.com, linux-kernel@vger.kernel.org, stable@vger.kernel.org References: <20261107213856462Jx8pIdgdtLvPLfOFTwV4X@zte.com.cn> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit On 11/7/26 14:38, shao.mingyin@zte.com.cn wrote: > From: Shao Mingyin > > mm/migrate: fix softlockup in do_pages_move() with huge page arrays > > do_pages_move() walks the user page array one page at a time. For each > entry it performs two get_user() calls, an mmap_read_lock()/unlock() > around a folio walk, and an optional store_status(); none of them has to > sleep when the arrays stay resident and the rwsem is uncontended. > move_pages_and_store_status() returns early while the page list is > empty, so an array whose entries all resolve to the same node can run > the whole loop without any scheduling point. nr_pages comes straight > from move_pages(), so a huge array can hold a CPU past the watchdog > threshold on a non-preemptible kernel; with KASAN and function tracing > enabled, ten million entries can exceed it. > > Add cond_resched() so that long calls yield periodically. > do_pages_stat() has the same problem and is being fixed separately. In > current mainline only alpha, hexagon and classic m68k can still select > PREEMPT_NONE, and they cannot enable CONFIG_NUMA, so this mainly > targets pre-v7.0 stable kernels. Please share a real kernel splat from a real system. -- Cheers, David