RE: [PATCH 2/2] cpufreq: ppc-corenet: remove per-cpu variable 'cpu_mask'

From: Yuantian Tang <Yuantian.Tang@freescale.com>
To: Viresh Kumar <viresh.kumar@linaro.org>
Cc: Rafael Wysocki <rjw@rjwysocki.net>,
	"linaro-kernel@lists.linaro.org" <linaro-kernel@lists.linaro.org>,
	"linux-pm@vger.kernel.org" <linux-pm@vger.kernel.org>,
	Hongbo Zhang <hongbo.zhang@freescale.com>,
	"LeoLi@freescale.com" <LeoLi@freescale.com>
Subject: RE: [PATCH 2/2] cpufreq: ppc-corenet: remove per-cpu variable 'cpu_mask'
Date: Tue, 2 Sep 2014 07:02:37 +0000	[thread overview]
Message-ID: <9fde1bf81522480484897416019b0ee9@BY2PR03MB570.namprd03.prod.outlook.com> (raw)
In-Reply-To: <CAKohpokQo=Jqgj2CzTH41WbD6F1GpdhksWdg0dm8WLN_CT5KkA@mail.gmail.com>

I am saying your patch 2 probably is wrong, not patch 1.
Consider following case:
On T4240 platform, we have 3 cluster with 8 cpu in each cluster.
We offline 4 5 6 7 cpu and then online them back.
Cpu 4's policy->cpus is 0, 1, 2, 3, 4 
Cpu 5's policy->cpus is 0, 1, 2, 3, 4, 5.
....
So cpu 4 and 5's policy->cpus are not right, they should be 0, 1, 2, 3, 4, 5, 6, 7.

Thanks,
Yuantian

> -----Original Message-----
> From: Viresh Kumar [mailto:viresh.kumar@linaro.org]
> Sent: Tuesday, September 02, 2014 2:49 PM
> To: Tang Yuantian-B29983
> Cc: Rafael Wysocki; linaro-kernel@lists.linaro.org; linux-pm@vger.kernel.org;
> Zhang Hongbo-B45939; Li Yang-Leo-R58472
> Subject: Re: [PATCH 2/2] cpufreq: ppc-corenet: remove per-cpu variable
> 'cpu_mask'
> 
> On 2 September 2014 12:16, Yuantian Tang <Yuantian.Tang@freescale.com>
> wrote:
> > Hello Viresh:
> >
> > Probably it is not right considering the CPU cluster and CPU hotplug case.
> 
> So in case of hotplug the worst that can happen is policy->cpu gets updated.
> But because we are all concerned about cpu_data here, which is stored in
> per-cpu variables and is updated for all online CPUs, it should work.
> 
> I would like to see how that fails :)