linux-kernel - Re: [PATCH] x86: Add check for number of available vectors before CPU down [v3]

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Message-ID: <20131223071240.GA18274@gchen.bj.intel.com>
Date:	Mon, 23 Dec 2013 02:12:40 -0500
From:	"Chen, Gong" <gong.chen@...ux.intel.com>
To:	Prarit Bhargava <prarit@...hat.com>
Cc:	linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
	Michel Lespinasse <walken@...gle.com>,
	Andi Kleen <ak@...ux.intel.com>,
	Seiji Aguchi <seiji.aguchi@....com>,
	Yang Zhang <yang.z.zhang@...el.com>,
	Paul Gortmaker <paul.gortmaker@...driver.com>,
	janet.morgan@...el.com, tony.luck@...el.com, ruiv.wang@...il.com
Subject: Re: [PATCH] x86: Add check for number of available vectors before
 CPU down [v3]

On Fri, Dec 20, 2013 at 10:50:09AM -0500, Prarit Bhargava wrote:
> +int check_vectors(void)
> +{
> +	int irq, cpu;
> +	unsigned int vector, this_count, count;
> +	struct irq_desc *desc;
> +	struct irq_data *data;
> +	struct cpumask *affinity;
> +
> +	this_count = 0;
> +	for (vector = FIRST_EXTERNAL_VECTOR; vector < NR_VECTORS; vector++) {
> +		irq = __this_cpu_read(vector_irq[vector]);
> +		if (irq >= 0) {
> +			desc = irq_to_desc(irq);
> +			data = irq_desc_get_irq_data(desc);
> +			affinity = data->affinity;
> +			if (irq_has_action(irq) || !irqd_is_per_cpu(data) ||
This line looks weird. Why counter will be increased once the irq has
action? Do you mean

if (irq_has_action(irq) && !irqd_is_per_cpu(data) &&
    !cpumask_subset(affinity, cpu_online_mask))


> +			    !cpumask_subset(affinity, cpu_online_mask))
It looks like cpu_online_mask will be updated until cpu_disable_common
is called, but your check_vectors is called before that.

[...]
>  {
> diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
> index 85dc05a..7ac6654 100644
> --- a/arch/x86/kernel/smpboot.c
> +++ b/arch/x86/kernel/smpboot.c
> @@ -1312,6 +1312,12 @@ void cpu_disable_common(void)
>  
>  int native_cpu_disable(void)
>  {
> +	int ret;
> +
> +	ret = check_vectors();
> +	if (ret)
> +		return ret;
> +
>  	clear_local_APIC();
>  
>  	cpu_disable_common();
> -- 
> 1.7.9.3
> 

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