Re: [Xen-devel] [PATCH v5 1/4] VT-d PI: track the number of vcpus on pi blocking list

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 16.08.17 at 07:14, <chao.gao@xxxxxxxxx> wrote:
> @@ -100,6 +101,24 @@ void vmx_pi_per_cpu_init(unsigned int cpu)
>      spin_lock_init(&per_cpu(vmx_pi_blocking, cpu).lock);
>  }
>  
> +static void vmx_pi_add_vcpu(struct pi_blocking_vcpu *pbv,
> +                            struct vmx_pi_blocking_vcpu *vpbv)
> +{
> +    ASSERT(spin_is_locked(&vpbv->lock));

You realize this is only a very weak check for a non-recursive lock?

> +    add_sized(&vpbv->counter, 1);
> +    ASSERT(read_atomic(&vpbv->counter));

Why add_sized() and read_atomic() when you hold the lock?

Jan


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