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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=Ppjq6uci; 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 F3FEB606A31A; Wed, 28 Oct 2026 08:37:48 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=Ppjq6uci Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5CCC61F01825; Wed, 28 Oct 2026 08:37:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793176668; bh=1wbs7cHydDEQXXO5KItG+AMA3doDxVoVAxLbCzDRe70=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=Ppjq6ucixIquylI1RXa0glpRlIx0VRokubeu3+Rd9Zd3zOXS9VnLl/cf7El20ued2 LHGK6Xk9IQaRqA1ZpE5lW55bE8uTquQAGIOd9nbpx+msITLI5rBfXXBi6zLH41Zeqc PQVQTbbhTl+Xu3JKPXDUPG5SFtltCsZNT5zDz5R5fMPIh9kI/s6nMR6wCLH/WBSttZ Jd5uHYmnCRco+nGQQ0WjggVO4uKe9cQrI20/3HnGRX8jkvjhI3JLTfX7mJMkM07Cdu F2b+fzMNBq2vYgLkkqQ8IJadCUPcQEYgH5F/oqVQGjN5I00CKnmk+1zKvUPVkVo3LC m4OYLuMKXTIMQ== Message-ID: <5e980194-d892-4b68-80fe-612c910c29d7@kernel.org> Date: Wed, 28 Oct 2026 09:37:39 +0100 X-Mailing-List: linux-trace-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 v3 0/8] mm: fix allocator races with memory hotplug To: "Gregory Price (Meta)" , linux-mm@kvack.org Cc: linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, linux-rt-devel@lists.linux.dev, kernel-team@meta.com, akpm@linux-foundation.org, mhocko@suse.com, rientjes@google.com, shakeel.butt@linux.dev, rostedt@goodmis.org, mhiramat@kernel.org, mathieu.desnoyers@efficios.com, muchun.song@linux.dev, osalvador@suse.de, ljs@kernel.org, liam@infradead.org, vbabka@kernel.org, rppt@kernel.org, surenb@google.com, brendan.jackman@linux.dev, hannes@cmpxchg.org, ziy@nvidia.com, bigeasy@linutronix.de, clrkwllms@kernel.org, mgorman@techsingularity.net, anshuman.khandual@arm.com, Bessel.Wang@huawei.com, jiang.liu@huawei.com References: <20261021023940.1940971-1-gourry@gourry.net> 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 10/21/26 04:39, Gregory Price (Meta) wrote: > Eight fixes for allocator paths that can act on state another CPU is > updating: zonelists rebuilt by memory hotplug, and the pagesets of a > zone that offlining empties. > > I've packaged these together because they're all related to hotplug. > > *** Backport note - Patches 5-7 build on patch 1: without it, their > retry is compiled out when CONFIG_MEMORY_HOTREMOVE=n. > > Most of these race conditions stem from zonelists being re-ordered > in-place at runtime during hotplug. The result is a mixture of failed > allocations, NULL dereferences, incorrect placement (GFP_KERNEL in > ZONE_MOVABLE), node misplacement, or incorrectly allowing hugetlb / > contig allocations on a node/zone otherwise not eligible. > > Most of these are incredibly narrow race conditions, but since the most > likely impacted machines are VMs with memory hotplug, the narrow > condition can more easily occur when a vCPU takes a long interrupt / VM > exit of some kind. I've made all of these race conditions > deterministics with a kprobe reproduction module described below. What's the status of this? "memory hotplug" caught my attention, but then then is all page_alloc material :) -- Cheers, David