probe the cpu idle event

["Li Guanglei" <guanglei at cn dot ibm dot com>]

Hi folks,
 In my tapsets, I tried to probe cpu idle event(on SMP):

 probe addevent.backtrace.cpuidle
       = kernel.inline("idle_balance")

 But if idle_balance successfully pulled tasks from other CPUs onto 
current CPU, the scheduler will choose the newly migrated task to run 
instead of idle task. So this probe definition is not accurate.

It seems that the following probe will correctly reflect the idle 
event:
  probe addevent.backtrace.cpuidle
       = kernel.inline("idle_balance").return
  {
     if(! runqueue->nr_running)  //pseudo code
            then scheduler will pick idle task to run
  }

But  currently systemtap doesn't support return of inline function.

Another way is to probe __switch_to to check if next->pid is zero. 
But put a probe handler onto __switch_to is more expensive than onto 
idle_balance.

So anybody has some good ideas of catching the cpu idle events? Or is 
there a plan to implement the return of inline function?