Messages in this thread | | | Date | Fri, 29 Jan 2016 16:33:39 -0800 | From | Saravana Kannan <> | Subject | Re: [RFC PATCH 11/19] cpufreq: assert policy->rwsem is held in __cpufreq_governor |
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On 01/12/2016 02:20 AM, Viresh Kumar wrote: > On 11-01-16, 17:35, Juri Lelli wrote: >> __cpufreq_governor works on policy, so policy->rwsem has to be held. >> Add assertion for such condition. >> >> Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net> >> Cc: Viresh Kumar <viresh.kumar@linaro.org> >> Signed-off-by: Juri Lelli <juri.lelli@arm.com> >> --- >> drivers/cpufreq/cpufreq.c | 3 +++ >> 1 file changed, 3 insertions(+) >> >> diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c >> index f1f9fbc..e7fc5c9 100644 >> --- a/drivers/cpufreq/cpufreq.c >> +++ b/drivers/cpufreq/cpufreq.c >> @@ -1950,6 +1950,9 @@ static int __cpufreq_governor(struct cpufreq_policy *policy, >> /* Don't start any governor operations if we are entering suspend */ >> if (cpufreq_suspended) >> return 0; >> + >> + lockdep_assert_held(&policy->rwsem); >> + > > We had an ABBA problem with the EXIT governor callback and so this > rwsem is dropped just before that from set_policy().. > > commit 955ef4833574 ("cpufreq: Drop rwsem lock around > CPUFREQ_GOV_POLICY_EXIT") >
AFAIR, the ABBA issue was between the sysfs lock and the policy lock. The fix for that issue should not be dropping the lock around POLICY_EXIT. The proper fix is to have the governor "export" the attributes it wants to add/remove and have the cpufreq framework do the adding/removing of the attributes from sysfs for the governor.
Thanks, Saravana
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