Re: [PATCH v3 09/10] xen/arm: Free memory allocated for sibling/core maps on CPU hot-unplug

[Julien Grall <julien.grall@arm.com>]

Hi Mirela,

On 27/04/18 18:12, Mirela Simonovic wrote:
> The memory allocated in setup_cpu_sibling_map() when a CPU is hotplugged
> has to be freed when the CPU is hot-unplugged. This is done in
> remove_cpu_sibling_map() and called when the CPU dies. The call to
> remove_cpu_sibling_map() is made from a notifier callback when
> CPU_DEAD event is received.
> 
> Signed-off-by: Mirela Simonovic <mirela.simonovic@aggios.com>
> 
> ---
> CC: Stefano Stabellini <sstabellini@kernel.org>
> CC: Julien Grall <julien.grall@arm.com>
> ---
> Changes in v3:
> -Use notifier to trigger remove_cpu_sibling_map() when the CPU dies.
> ---
>   xen/arch/arm/smpboot.c | 34 ++++++++++++++++++++++++++++++++++
>   1 file changed, 34 insertions(+)
> 
> diff --git a/xen/arch/arm/smpboot.c b/xen/arch/arm/smpboot.c
> index ad1f6b751b..b833e3a754 100644
> --- a/xen/arch/arm/smpboot.c
> +++ b/xen/arch/arm/smpboot.c
> @@ -89,6 +89,12 @@ static void setup_cpu_sibling_map(int cpu)
>       cpumask_set_cpu(cpu, per_cpu(cpu_core_mask, cpu));
>   }
>   
> +static void remove_cpu_sibling_map(int cpu)
> +{
> +    free_cpumask_var(per_cpu(cpu_sibling_mask, cpu));
> +    free_cpumask_var(per_cpu(cpu_core_mask, cpu));
> +}
> +
>   void __init
>   smp_clear_cpu_maps (void)
>   {
> @@ -499,6 +505,34 @@ void __cpu_die(unsigned int cpu)
>       smp_mb();
>   }
>   
> +static int cpu_smpboot_callback(
> +    struct notifier_block *nfb, unsigned long action, void *hcpu)
> +{
> +    unsigned int cpu = (unsigned long)hcpu;
> +
> +    switch ( action )
> +    {
> +    case CPU_DEAD:
> +        remove_cpu_sibling_map(cpu);
> +        break;
> +    default:
> +        break;
> +    }
> +
> +    return NOTIFY_DONE;
> +}
> +
> +static struct notifier_block cpu_smpboot_nfb = {
> +    .notifier_call = cpu_smpboot_callback,
> +};
> +
> +static int __init cpu_smpboot_notifier_init(void)
> +{
> +    register_cpu_notifier(&cpu_smpboot_nfb);
> +    return 0;
> +}
> +__initcall(cpu_smpboot_notifier_init);

I think this notifiers should go in preinit smp to cover the case where 
a secondary CPU dies beforehand the initcall.

Cheers,

-- 
Julien Grall

_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xenproject.org
https://lists.xenproject.org/mailman/listinfo/xen-devel