[PATCH RFC idle 2/3] arm: Avoid invoking RCU when CPU is idle

On Fri, 2012-02-03 at 11:40 -0800, Paul E. McKenney wrote:

So the idea is that if you have a trace event that is to be used in idle,
you use TRACE_EVENT_IDLE() rather than TRACE_EVENT() to declare that
trace event?  That would work for me, and might make for fewer changes
for the architecture guys.  Also, this should address the code-size
concerns we discussed yesterday.

So sounds good!

Is a DEFINE_EVENT_IDLE() also needed?  Or prehaps a
DECLARE_EVENT_CLASS_IDLE()?  My guess is "yes" for at least one of the
two based on include/trace/events/power.h.

I'll have to take a look. I may even find a better way to do this too.

I will keep RCU_NONIDLE() for at least a little while (reworking comments
to point out TRACE_EVENT_IDLE() and friends) in case there turn out to
be non-tracepoint uses of RCU in the idle loop.

OK, I'll take a crack at this next Monday.

-- Steve