Re: [Xen-devel] [PATCH 09/18] xen/arm: Add rcu_barrier() before enabling non-boot CPUs on resume

[Julien Grall <julien.grall@xxxxxxx>]

Hi,

On 12/11/2018 11:30, Mirela Simonovic wrote:
> The rcu_barrier() has to be added to ensure that the per cpu area is
> freed before a non-boot CPU tries to initialize it (_free_percpu_area()
> has to be called before the init_percpu_area()). This scenario occurs
> when non-boot CPUs are hot-unplugged on suspend and hotplugged on resume.
From the description, this is a bug introduced by the previous patch. So should 
merged in it.
The commit message will also need to explain why the rcu_barrier() is required.

Cheers,

> Signed-off-by: Mirela Simonovic <mirela.simonovic@xxxxxxxxxx>
> Signed-off-by: Saeed Nowshadi <saeed.nowshadi@xxxxxxxxxx>
> ---
>   xen/arch/arm/suspend.c | 1 +
>   1 file changed, 1 insertion(+)
>
> diff --git a/xen/arch/arm/suspend.c b/xen/arch/arm/suspend.c
> index dae1b1f7d6..8e8e531d61 100644
> --- a/xen/arch/arm/suspend.c
> +++ b/xen/arch/arm/suspend.c
> @@ -133,6 +133,7 @@ static long system_suspend(void *data)
>       system_state = SYS_STATE_resume;
>   
>   resume_nonboot_cpus:
> +    rcu_barrier();
>       enable_nonboot_cpus();
>       thaw_domains();
>       system_state = SYS_STATE_active;
--
Julien Grall

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