tracing: generate RCU warnings even when tracepoints are disabled

tracing: generate RCU warnings even when tracepoints are disabled

Dave Jones reported seeing a bug from one of my TLB tracepoints:

	http://lkml.kernel.org/r/20140806181801.GA4605@redhat.com

I've been running these patches for months and never saw this.
But, a big chunk of my testing, especially with all the debugging
enabled, was in a vm where intel_idle doesn't work.  On the
systems where I was using intel_idle, I never had lockdep enabled
and this tracepoint on at the same time.

This patch ensures that whenever we have lockdep available, we do
_some_ RCU activity at the site of the tracepoint, despite
whether the tracepoint's condition matches or even if the
tracepoint itself is completely disabled.  This is a bit of a
hack, but it is pretty self-contained.

I confirmed that with this patch plus lockdep I get the same
splat as Dave Jones did, but without enabling the tracepoint
explicitly.

Link: http://lkml.kernel.org/p/20140807175204.C257CAC5@viggo.jf.intel.com
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Dave Hansen <dave@sr71.net>
Cc: Dave Jones <davej@redhat.com>,
Cc: paulmck@linux.vnet.ibm.com
Cc: Ingo Molnar <mingo@redhat.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>