linux-kernel - Re: [PATCH v4 14/18] x86/intel

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Date:   Mon, 17 Oct 2016 23:27:59 +0200 (CEST)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Fenghua Yu <fenghua.yu@...el.com>
cc:     "H. Peter Anvin" <h.peter.anvin@...el.com>,
        Ingo Molnar <mingo@...e.hu>, Tony Luck <tony.luck@...el.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Stephane Eranian <eranian@...gle.com>,
        Borislav Petkov <bp@...e.de>,
        Dave Hansen <dave.hansen@...el.com>,
        Nilay Vaish <nilayvaish@...il.com>, Shaohua Li <shli@...com>,
        David Carrillo-Cisneros <davidcc@...gle.com>,
        Ravi V Shankar <ravi.v.shankar@...el.com>,
        Sai Prakhya <sai.praneeth.prakhya@...el.com>,
        Vikas Shivappa <vikas.shivappa@...ux.intel.com>,
        linux-kernel <linux-kernel@...r.kernel.org>, x86 <x86@...nel.org>
Subject: Re: [PATCH v4 14/18] x86/intel_rdt: Add cpus file

On Fri, 14 Oct 2016, Fenghua Yu wrote:
>  static int intel_rdt_offline_cpu(unsigned int cpu)
>  {
>  	struct rdt_resource *r;
> +	struct rdtgroup *rdtgrp;
> +	struct list_head *l;
>  
>  	mutex_lock(&rdtgroup_mutex);
>  	for_each_rdt_resource(r)
>  		update_domain(cpu, r, 0);
> +	list_for_each(l, &rdt_all_groups) {

list_for_each_entry ...

> +		rdtgrp = list_entry(l, struct rdtgroup, rdtgroup_list);
> +		if (cpumask_test_and_clear_cpu(cpu, &rdtgrp->cpu_mask))
> +			break;

> +static ssize_t rdtgroup_cpus_write(struct kernfs_open_file *of,
> +				   char *buf, size_t nbytes, loff_t off)
> +{
     ....
> +	/* Are trying to drop some cpus from this group? */

  	/* Check whether cpus are dropped from this group */

> +	cpumask_andnot(tmpmask, &rdtgrp->cpu_mask, newmask);
> +	if (cpumask_weight(tmpmask)) {
> +		/* Can't drop from default group */
> +		if (rdtgrp == &rdtgroup_default) {
> +			ret = -EINVAL;
> +			goto end;
> +		}
> +		/* Give any dropped cpus to rdtgroup_default */
> +		cpumask_or(&rdtgroup_default.cpu_mask,
> +			   &rdtgroup_default.cpu_mask, tmpmask);
> +		for_each_cpu(cpu, tmpmask)
> +			per_cpu(cpu_closid, cpu) = 0;
> +	}
> +
> +	/*
> +	 * If we added cpus, remove them from previous group that owned them
> +	 * and update per-cpu rdtgroup pointers to refer to us

s/per-cpu rdtgroup pointers to refer to us/the per-cpu closid/

> +	 */
> +	cpumask_andnot(tmpmask, newmask, &rdtgrp->cpu_mask);
> +	if (cpumask_weight(tmpmask)) {
> +		struct list_head *l;
> +
> +		list_for_each(l, &rdt_all_groups) {
> +			r = list_entry(l, struct rdtgroup, rdtgroup_list);

Once more: list_for_each_entry()

> @@ -582,6 +698,10 @@ static int rdtgroup_rmdir(struct kernfs_node *kn)
>  		return -EPERM;
>  	}
>  
> +	/* Give any CPUs back to the default group */
> +	cpumask_or(&rdtgroup_default.cpu_mask,
> +		   &rdtgroup_default.cpu_mask, &rdtgrp->cpu_mask);

What resets the per-cpu closid to 0?

Thanks,

	tglx