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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 2026-03-20 09:31, Mathieu Desnoyers wrote: > On 2026-03-20 09:21, Harry Yoo (Oracle) wrote: >> On Fri, Mar 20, 2026 at 08:35:46AM -0400, Mathieu Desnoyers wrote: >>> On 2026-03-20 00:17, Harry Yoo wrote: >>> [...] >>>>> [1]: https://lore.kernel.org/20260227153730.1556542-4- >>>>> mathieu.desnoyers@efficios.com/ >>>> >>>> @Mathieu: In patch 1/3 description, >>>>> Changes since v7: >>>>> - Explicitly initialize the subsystem from start_kernel() right >>>>>     after mm_core_init() so it is up and running before the >>>>> creation of >>>>>     the first mm at boot. >>>> >>>> But how does this work when someone calls mm_cpumask() on init_mm >>>> early? >>>> Looks like it will behave incorrectly because get_rss_stat_items_size() >>>> returns zero? >>> >>> It doesn't work as expected at all. I missed that all users of >>> mm_cpumask() >>> end up relying on get_rss_stat_items_size(), which now calls >>> percpu_counter_tree_items_size(), which depends on initialization from >>> percpu_counter_tree_subsystem_init(). >>> >>> If you add a call to percpu_counter_tree_subsystem_init in >>> arch/powerpc/kernel/setup_arch() just before: [...] One thing we could do to catch this kind of init sequence issue is to add a WARN_ON_ONCE in percpu_counter_tree_items_size: size_t percpu_counter_tree_items_size(void) { if (WARN_ON_ONCE(!nr_cpus_order)) return 0; return counter_config->nr_items * sizeof(struct percpu_counter_tree_level_item); } Thanks, Mathieu -- Mathieu Desnoyers EfficiOS Inc. https://www.efficios.com