linux-kernel - Re: [PATCH V2] acpi-cpufreq: replace per_cpu with driver

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Message-ID: <57468987.NPFzCAAv5k@vostro.rjw.lan>
Date:	Fri, 10 Jul 2015 03:16:49 +0200
From:	"Rafael J. Wysocki" <rjw@...ysocki.net>
To:	Pan Xinhui <xinhuix.pan@...el.com>
Cc:	Viresh Kumar <viresh.kumar@...aro.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	linux-pm@...r.kernel.org, "mnipxh@....com" <mnipxh@....com>,
	"yanmin_zhang@...ux.intel.com" <yanmin_zhang@...ux.intel.com>
Subject: Re: [PATCH V2] acpi-cpufreq: replace per_cpu with driver_data of policy

On Thursday, July 09, 2015 09:28:30 AM Pan Xinhui wrote:
> hi, Rafael
> 	thanks for your kind reply. :)
> 
> On 2015年07月09日 08:20, Rafael J. Wysocki wrote:
> > On Tuesday, July 07, 2015 08:04:43 PM Viresh Kumar wrote:
> >> On 07-07-15, 20:43, Pan Xinhui wrote:
> >>>
> >>> Drivers can store their internal per-policy information in
> >>> policy->driver_data, lets use it.
> >>>
> >>> we have benefits after this replacing.
> >>> 1) memory saving.
> >>> 2) policy is shared by several cpus, per_cpu seems not correct. using
> >>> *driver_data* is more reasonable.
> >>> 3) fix a memory leak in acpi_cpufreq_cpu_exit. as policy->cpu might
> >>> change during cpu hotplug. So sometimes we cant't free *data*, use
> >>> *driver_data* to fix it.
> >>> 4) fix a zero return value of get_cur_freq_on_cpu. Only per_cpu of
> >>> policy->cpu is set to *data*, if we try to get cpufreq on other cpus, we
> >>> get zero instead of correct values. Use *driver_data* to fix it.
> >>>
> >>> Signed-off-by: Pan Xinhui <xinhuix.pan@...el.com>
> >>> ---
> >>> Changes from V1:
> >>> 	codes style fix, comments update
> >>> 	move cpufreq_cpu_put(policy) after we get *driver_data*
> >>> ---
> >>>  drivers/cpufreq/acpi-cpufreq.c | 40 ++++++++++++++++++++++------------------
> >>>  1 file changed, 22 insertions(+), 18 deletions(-)
> >>
> >> Acked-by: Viresh Kumar <viresh.kumar@...aro.org>
> > 
> > OK
> > 
> > Does it fix any recent regressions or is it just an old bug?
> > 
> 
> This patch achieve old bug fix and codes improvements. In past days, policy has no field *driver_data*, So
> acpi-cpufreq driver has to use per_cpu to store some extra information. But it did not take good care of every scenarios.
> Now cpufreq core makes awesome effort to store more per-policy information in policy. We can make use of this feature. So I
> cook this patch. :)

OK, patch applied, thanks!

> I am preparing two patches for other two issues in acpi-cpufreq driver based on this patch.
> I will fix them step by step. :)

Thanks for doing that!

Rafael

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