linux-kernel - Re: [PATCH] cpufreq, store_scaling_governor requires policy->rwsem to be held for duration of changing governors [v2]

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Message-ID: <53DAA95B.2040505@codeaurora.org>
Date:	Thu, 31 Jul 2014 13:38:51 -0700
From:	Saravana Kannan <skannan@...eaurora.org>
To:	Prarit Bhargava <prarit@...hat.com>
CC:	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	linux-kernel@...r.kernel.org,
	Viresh Kumar <viresh.kumar@...aro.org>,
	Lenny Szubowicz <lszubowi@...hat.com>, linux-pm@...r.kernel.org
Subject: Re: [PATCH] cpufreq, store_scaling_governor requires policy->rwsem
 to be held for duration of changing governors [v2]

On 07/31/2014 01:30 PM, Prarit Bhargava wrote:
>
>
> On 07/31/2014 04:24 PM, Saravana Kannan wrote:
>>
>> Prarit,
>>
>> I'm not an expert on sysfs locking, but I would think the specific sysfs lock
>> would depend on the file/attribute group. So, can you please try to hotplug a
>> core in/out (to trigger the POLICY_EXIT) and then read a sysfs file exported by
>> the governor? scaling_governor doesn't cut it since that file is not removed on
>> policy exit event to governor. If it's ondemand, try reading/write it's sampling
>> rate file.
>
> Thanks Saravana -- will do.  I will get back to you shortly on this.
>

Thanks. Btw, in case you weren't already aware of it. You'll have to 
hoplug out all the CPUs in a cluster to trigger a POLICY_EXIT for that 
cluster/policy.

-Saravana

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