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[173.79.60.52]) by smtp.gmail.com with ESMTPSA id 6a1803df08f44-91c47c96375sm132097726d6.33.2026.10.28.06.41.55 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 28 Oct 2026 06:41:56 -0700 (PDT) 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 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Subject: Re: [PATCH v3 0/8] mm: fix allocator races with memory hotplug From: "Gregory Price (Meta)" To: "David Hildenbrand (Arm)" Cc: "Gregory Price (Meta)" , linux-mm@kvack.org, 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 In-Reply-To: <5e980194-d892-4b68-80fe-612c910c29d7@kernel.org> References: <20261021023940.1940971-1-gourry@gourry.net> <5e980194-d892-4b68-80fe-612c910c29d7@kernel.org> Date: Wed, 28 Oct 2026 09:41:55 -0400 Message-Id: <179319491540.2032926.7199366288730313291.b4-reply@b4> X-Mailer: b4 0.17-dev On 2026-10-28 09:37 +0100, David Hildenbrand (Arm) wrote: > 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 :) > I have a v4 with the requested tweaks and some performance analysis, though i think there is some overlap with the other Fixes: series. I can send it out and if it helps i can pull together a report on overlap between the different Fixes: series. ~Gregory -- ~Gregory