On Thu, Sep 18, 2014 at 02:32:25PM -0400, Nicolas Pitre wrote:

On Thu, 18 Sep 2014, Paul E. McKenney wrote:

quoted

So what is it that you really need to do here?

In short, we don't want the cpufreq data to go away (see the 2 scenarios 
above) while the scheduler is looking at it.  The scheduler uses the 
provided accessors (see patch 2/2) so we can put any protection 
mechanism we want in them.  A simple spinlock could do just as well 
which should be good enough.

rq->lock disables interrupts so on that something like
kick_all_cpus_sync() will guarantee what you need --
wake_up_all_idle_cpus() will not.