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Date: Fri, 20 Oct 2017 11:03:03 +0200 (CEST)
From: Thomas Gleixner <tglx@linutronix.de>
To: Prarit Bhargava <prarit@redhat.com>
cc: linux-kernel@vger.kernel.org, Andi Kleen <ak@linux.intel.com>,
        Ingo Molnar <mingo@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>,
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Subject: Re: [PATCH 2/3 v3] x86/topology: Avoid wasting 128k for package id
 array
In-Reply-To: <20171019155713.27097-3-prarit@redhat.com>
Message-ID: <alpine.DEB.2.20.1710201058570.1882@nanos>
References: <20171019155713.27097-1-prarit@redhat.com> <20171019155713.27097-3-prarit@redhat.com>
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On Thu, 19 Oct 2017, Prarit Bhargava wrote:
>  static void remove_siblinginfo(int cpu)
>  {
> -	int sibling;
> +	int phys_pkg_id, sibling;
>  	struct cpuinfo_x86 *c = &cpu_data(cpu);
>  
>  	for_each_cpu(sibling, topology_core_cpumask(cpu)) {
> @@ -1529,6 +1526,12 @@ static void remove_siblinginfo(int cpu)
>  	cpumask_clear(topology_core_cpumask(cpu));
>  	c->phys_proc_id = 0;
>  	c->cpu_core_id = 0;
> +
> +	phys_pkg_id = c->phys_pkg_id;
> +	c->phys_pkg_id = U16_MAX;

This leaves c->logical_proc_set = 1, which is inconsistent at best. I have
no idea why we need this logical_proc_set flag at all.

> +	if (topology_phys_to_logical_pkg(phys_pkg_id) < 0)
> +		logical_packages--;

Now this has another issue. Depending on hotplug ordering the logical
package association can change across hotplug operations. I don't know it
that's an issue, but this needs to be analyzed before we merge that.

Thanks,

	tglx