linux-kernel - Re: [RFC][PATCH] cpufreq: Do not hold driver module references for additional policy CPUs

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Message-ID: <51FAB083.5050900@linux.vnet.ibm.com>
Date:	Fri, 02 Aug 2013 00:31:23 +0530
From:	"Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
CC:	Viresh Kumar <viresh.kumar@...aro.org>,
	Linux PM list <linux-pm@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>, cpufreq@...r.kernel.org,
	Lists linaro-kernel <linaro-kernel@...ts.linaro.org>
Subject: Re: [RFC][PATCH] cpufreq: Do not hold driver module references for
 additional policy CPUs

On 08/02/2013 12:31 AM, Rafael J. Wysocki wrote:
> On Thursday, August 01, 2013 11:36:49 PM Srivatsa S. Bhat wrote:
>> Its the cpufreq_cpu_get() hidden away in cpufreq_add_dev_symlink(). With
>> that taken care of, everything should be OK. Then we can change the
>> synchronization part to avoid using refcounts.
> 
> So I actually don't see why cpufreq_add_dev_symlink() needs to call
> cpufreq_cpu_get() at all, since the policy refcount is already 1 at the
> point it is called and the bumping up of the driver module refcount is
> pointless.
> 

Hmm, yes, it seems so.

> However, if I change that I also need to change the piece of code that
> calls the complementary cpufreq_cpu_put() and I kind of cannot find it.
> 

... I guess that's because you are looking at the code with your patch
applied (and your patch removed that _put()) ;-)

Its this part in __cpufreq_remove_dev():

1303         } else {
1304 
1305                 if (!frozen) {
1306                         pr_debug("%s: removing link, cpu: %d\n", __func__, cpu);
1307                         cpufreq_cpu_put(data);
1308                 }
1309 

 
Regards,
Srivatsa S. Bhat

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