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

From	Viresh Kumar <viresh.kumar@linaro.org>
Newsgroups	linux.kernel
Subject	Re: [RFC PATCH 16/19] cpufreq: hold policy->rwsem across CPUFREQ_GOV_POLICY_EXIT
Date	2016-01-12 12:20 +0100
Message-ID	<qQ59w-8S-25@gated-at.bofh.it> (permalink)
References	<qPOBH-5zs-9@gated-at.bofh.it> <qPOBJ-5zs-41@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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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

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[RFC PATCH 16/19] cpufreq: hold policy->rwsem across CPUFREQ_GOV_POLICY_EXIT Juri Lelli <juri.lelli@arm.com> - 2016-01-11 18:40 +0100
  Re: [RFC PATCH 16/19] cpufreq: hold policy->rwsem across  CPUFREQ_GOV_POLICY_EXIT Viresh Kumar <viresh.kumar@linaro.org> - 2016-01-12 12:20 +0100

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