linux-kernel - Re: cpu hotplug: possible_cpus broken (again?) next-20130607

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Message-ID: <51B7BFB0.8080401@sr71.net>
Date:	Tue, 11 Jun 2013 17:24:16 -0700
From:	Dave Hansen <dave@...1.net>
To:	Youquan Song <youquan.song@...ux.intel.com>
CC:	Toshi Kani <toshi.kani@...com>, "Rafael J. Wysocki" <rjw@...k.pl>,
	youquan.song@...el.com, LKML <linux-kernel@...r.kernel.org>,
	Stephen Rothwell <sfr@...b.auug.org.au>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	akpm@...ux-foundation.org
Subject: Re: cpu hotplug:  possible_cpus broken (again?) next-20130607

On 06/12/2013 05:03 AM, Youquan Song wrote:
> +#ifdef CONFIG_SMP
> +              /* return when cpu number greater than maximum number of
> CPUs */
> +               if (setup_max_cpus <= num_online_cpus() + 1) {
> +                       cpu_hotplug_driver_unlock();
> +                       return -EINVAL;
> +               }
> +#endif
>                 from_nid = cpu_to_node(cpuid);
>                 ret = cpu_up(cpuid);

Your patch is line-wrapped.

Also, the #ifdef is unnecessary.  If CONFIG_SMP is off:

	static const unsigned int setup_max_cpus = NR_CPUS;
	#define num_online_cpus() 1U

The compiler will take care of optimizing out the the if() without the
explicit #ifdef.

Also, the +1 looks goofy to me.  Doesn't this do the same thing (and
isn't it much easier to read)?

	if (num_online_cpus() >= setup_max_cpus)
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