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Date: Wed, 30 Nov 2011 16:11:31 -0800
From: Andrew Morton <akpm@linux-foundation.org>
To: Dimitri Sivanich <sivanich@sgi.com>
Cc: linux-kernel@vger.kernel.org, Thomas Gleixner <tglx@linutronix.de>
Subject: Re: [PATCH] specific do_timer_cpu value for nohz off mode
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On Wed, 30 Nov 2011 09:29:59 -0600
Dimitri Sivanich <sivanich@sgi.com> wrote:

> +static ssize_t sysfs_store_do_timer_cpu(struct sys_device *dev,
> +						struct sysdev_attribute *attr,
> +						const char *buf, size_t size)
> +{
> +	struct sysdev_ext_attribute *ea = SYSDEV_TO_EXT_ATTR(attr);
> +	unsigned int new;
> +	int rv;
> +
> +#ifdef CONFIG_NO_HZ
> +	/* nohz mode not supported */
> +	if (tick_nohz_enabled)
> +		return -EINVAL;
> +#endif
> +
> +	rv = kstrtouint(buf, 0, &new);
> +	if (rv)
> +		return rv;
> +
> +	if (new >= NR_CPUS || !cpu_online(new))
> +		return -ERANGE;
> +
> +	*(unsigned int *)(ea->var) = new;
> +	return size;
> +}

checkpatch tells us:

WARNING: usage of NR_CPUS is often wrong - consider using cpu_possible(), num_possible_cpus(), for_each_possible_cpu(), etc

I think the check can just be removed?  Surely cpu_online(1000000000)
will return false?