On 2026-03-20 00:17, Harry Yoo wrote:
[...]
[1]:
https://lore.kernel.org/[email protected]/
@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:
VM_WARN_ON(cpumask_test_cpu(smp_processor_id(), mm_cpumask(&init_mm)));
cpumask_set_cpu(smp_processor_id(), mm_cpumask(&init_mm));
Does the warning go away ?
Alternatively, would could use a lazy initialization invoking
percpu_counter_tree_subsystem_init from percpu_counter_tree_items_size
when the initialization is not already done.
Any preference ?
Mathieu
--
Mathieu Desnoyers
EfficiOS Inc.
https://www.efficios.com
