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" <r...@rjwysocki.net>
Cc: Viresh Kumar <viresh.ku...@linaro.org>
Signed-off-by: Juri Lelli <juri.le...@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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