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SubjectRe: [PATCH v3] NUMA: Early use of cpu_to_node() returns 0 instead of the correct node id
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On Thu, 25 Jan 2024 22:44:51 PST (-0800), shijie@os.amperecomputing.com wrote:
> During the kernel booting, the generic cpu_to_node() is called too early in
> arm64, powerpc and riscv when CONFIG_NUMA is enabled.
>
> There are at least four places in the common code where
> the generic cpu_to_node() is called before it is initialized:
> 1.) early_trace_init() in kernel/trace/trace.c
> 2.) sched_init() in kernel/sched/core.c
> 3.) init_sched_fair_class() in kernel/sched/fair.c
> 4.) workqueue_init_early() in kernel/workqueue.c
>
> In order to fix the bug, the patch introduces early_numa_node_init()
> which is called after smp_prepare_boot_cpu() in start_kernel.
> early_numa_node_init will initialize the "numa_node" as soon as
> the early_cpu_to_node() is ready, before the cpu_to_node() is called
> at the first time.
>
> Signed-off-by: Huang Shijie <shijie@os.amperecomputing.com>
> ---
> v2 --> v3:
> Do not change the cpu_to_node to function pointer.
> Introduce early_numa_node_init() which initialize
> the numa_node at an early stage.
>
> v2: https://lore.kernel.org/all/20240123045843.75969-1-shijie@os.amperecomputing.com/
>
> v1 --> v2:
> In order to fix the x86 compiling error, move the cpu_to_node()
> from driver/base/arch_numa.c to driver/base/node.c.
>
> v1: http://lists.infradead.org/pipermail/linux-arm-kernel/2024-January/896160.html
>
> An old different title patch:
> http://lists.infradead.org/pipermail/linux-arm-kernel/2024-January/895963.html
>
> ---
> init/main.c | 14 ++++++++++++++
> 1 file changed, 14 insertions(+)
>
> diff --git a/init/main.c b/init/main.c
> index e24b0780fdff..39efe5ed58a0 100644
> --- a/init/main.c
> +++ b/init/main.c
> @@ -870,6 +870,19 @@ static void __init print_unknown_bootoptions(void)
> memblock_free(unknown_options, len);
> }
>
> +static void __init early_numa_node_init(void)
> +{
> +#ifdef CONFIG_USE_PERCPU_NUMA_NODE_ID
> +#ifndef cpu_to_node
> + int cpu;
> +
> + /* The early_cpu_to_node() should be ready here. */
> + for_each_possible_cpu(cpu)
> + set_cpu_numa_node(cpu, early_cpu_to_node(cpu));
> +#endif
> +#endif
> +}
> +
> asmlinkage __visible __init __no_sanitize_address __noreturn __no_stack_protector
> void start_kernel(void)
> {
> @@ -900,6 +913,7 @@ void start_kernel(void)
> setup_nr_cpu_ids();
> setup_per_cpu_areas();
> smp_prepare_boot_cpu(); /* arch-specific boot-cpu hooks */
> + early_numa_node_init();
> boot_cpu_hotplug_init();
>
> pr_notice("Kernel command line: %s\n", saved_command_line);

Acked-by: Palmer Dabbelt <palmer@rivosinc.com> # RISC-V

I don't really understand the init/main.c stuff all that well, I'm
adding Andrew as it looks like he's been merging stuff here.

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