linux-kernel - Re: [PATCH 2/3] x86/intel_rdt: Return state to default on umount

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Message-ID: <alpine.DEB.2.20.1611151827310.3595@nanos>
Date:   Tue, 15 Nov 2016 18:28:14 +0100 (CET)
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>,
        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 2/3] x86/intel_rdt: Return state to default on umount

On Tue, 15 Nov 2016, Thomas Gleixner wrote:

> On Fri, 11 Nov 2016, Fenghua Yu wrote:
> > @@ -801,6 +801,7 @@ static void rmdir_all_sub(void)
> >  {
> >  	struct rdtgroup *rdtgrp, *tmp;
> >  	struct task_struct *p, *t;
> > +	int cpu;
> >  
> >  	/* move all tasks to default resource group */
> >  	read_lock(&tasklist_lock);
> > @@ -819,10 +820,19 @@ static void rmdir_all_sub(void)
> >  		/* Remove each rdtgroup other than root */
> >  		if (rdtgrp == &rdtgroup_default)
> >  			continue;
> > +
> > +		/* Give any CPUs back to the default group */
> > +		cpumask_or(&rdtgroup_default.cpu_mask,
> > +			   &rdtgroup_default.cpu_mask, &rdtgrp->cpu_mask);
> 
> That's a pointless exercise. We can simply copy cpu_online_mask to the
> default group mask and be done with it. I'll fix that up.

Actually we cannot. A CPU which already run the offline callback might
still be marked online. So the above is correct.

Thanks,

	tglx