On Wed, Mar 16, 2016 at 4:35 PM, Peter Zijlstra [off-list ref] wrote:

On Wed, Mar 16, 2016 at 03:52:28PM +0100, Rafael J. Wysocki wrote:

quoted

+/**
+ * cpufreq_enable_fast_switch - Enable fast frequency switching for policy.
+ * @policy: cpufreq policy to enable fast frequency switching for.
+ *
+ * Try to enable fast frequency switching for @policy.
+ *
+ * The attempt will fail if there is at least one transition notifier registered
+ * at this point, as fast frequency switching is quite fundamentally at odds
+ * with transition notifiers.  Thus if successful, it will make registration of
+ * transition notifiers fail going forward.
+ *
+ * Call under policy->rwsem.

Nobody reads a comment..

quoted

+ */
+void cpufreq_enable_fast_switch(struct cpufreq_policy *policy)
+{

        lockdep_assert_held(&policy->rwsem);

While everybody complains when there's a big nasty splat in their dmesg
;-)

OK