Re: [PATCH] xen/smp: Use die_complete completion when taking CPU down

From: Ingo Molnar
Date: Thu Oct 16 2014 - 03:31:00 EST



* Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx> wrote:

> diff --git a/arch/x86/xen/smp.c b/arch/x86/xen/smp.c
> index 8650cdb..4da0008 100644
> --- a/arch/x86/xen/smp.c
> +++ b/arch/x86/xen/smp.c
> @@ -498,6 +498,7 @@ static int xen_cpu_disable(void)
> if (cpu == 0)
> return -EBUSY;
>
> + init_completion(&per_cpu(die_complete, smp_processor_id()));
> cpu_disable_common();
>
> load_cr3(swapper_pg_dir);
> @@ -510,6 +511,9 @@ static void xen_cpu_die(unsigned int cpu)
> current->state = TASK_UNINTERRUPTIBLE;
> schedule_timeout(HZ/10);
> }
> +
> + wait_for_completion_timeout(&per_cpu(die_complete, cpu), HZ);
> +
> xen_smp_intr_free(cpu);
> xen_uninit_lock_cpu(cpu);
> xen_teardown_timer(cpu);

So why not put it into cpu_disable_common() and do the same
change for native_cpu_disable()?

Likewise, the waiting bit should be put into a common function as
well (newly introduced, if need to be), we don't want to expose
internal x86 core data structures to the Xen guest code.

Thanks,

Ingo
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