linux-kernel - Re: [RFC PATCH 16/19] cpufreq: hold policy->rwsem across CPUFREQ_GOV_POLICY

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Date:	Tue, 12 Jan 2016 16:39:55 +0530
From:	Viresh Kumar <viresh.kumar@...aro.org>
To:	Juri Lelli <juri.lelli@....com>
Cc:	linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
	peterz@...radead.org, rjw@...ysocki.net, mturquette@...libre.com,
	steve.muckle@...aro.org, vincent.guittot@...aro.org,
	morten.rasmussen@....com, dietmar.eggemann@....com
Subject: Re: [RFC PATCH 16/19] cpufreq: hold policy->rwsem across
 CPUFREQ_GOV_POLICY_EXIT

On 11-01-16, 17:35, Juri Lelli wrote:
> There are no good reasons why policy->rwsem cannot be hold across calls to
> __cpufreq_governor with CPUFREQ_GOV_POLICY_EXIT event.
> 
> Remove {up,down}_write across such call sites. This also verify assertion
> that policy->rwsem is always hold when calling into __cpufreq_governor.

Test on X86 with prove_locking etc enabled.. and try running tests
from my cpufreq-test repo. There were real concerns. Over that, I have
identified the issue completely, as to why the ABBA dependency I
mentioned earlier is there. You can find that in the branch I shared
with you earlier.

commit 57714d5b1778 ("cpufreq: Access governor's sysfs attributes without 'policy->rwsem'")

-- 
viresh