Tracing of power:power_start events doesn't work

["Ronny Tschüter" <Ronny.Tschueter@tu-dresden.de>]

I use Linux performance counters to trace some performance related 
events. Unfortunately power:power_start events are not reported on my 
machine. In /drivers/acpi/processor_idle.c I found three different ways 
to call a C-state, but only one way (via architectural FFH based C-state 
and using MONITOR/MWAIT) is currently instrumented. Here is my patch to 
instrument the remaining two possibilities:

diff --git a/drivers/acpi/processor_idle.c b/drivers/acpi/processor_idle.c
index b1b3856..08e7c42 100644
--- a/drivers/acpi/processor_idle.c
+++ b/drivers/acpi/processor_idle.c
@@ -43,6 +43,7 @@
  #include <linux/clockchips.h>
  #include <linux/cpuidle.h>
  #include <linux/irqflags.h>
+#include <trace/events/power.h>

  /*
   * Include the apic definitions for x86 to have the APIC timer related 
defines
@@ -136,6 +137,7 @@ static void acpi_safe_halt(void)
       */
      smp_mb();
      if (!need_resched()) {
+        trace_power_start(POWER_CSTATE,1);
          safe_halt();
          local_irq_disable();
      }
@@ -797,6 +799,10 @@ static inline void acpi_idle_do_entry(struct 
acpi_processor_cx *cx)
      } else {
          int unused;
          /* IO port based C-state */
+        trace_power_start(POWER_CSTATE,
+        cx->type == ACPI_STATE_C1 ? 1 :
+        cx->type == ACPI_STATE_C2 ? 2 :
+        3);
          inb(cx->address);
          /* Dummy wait op - must do something useless after P_LVL2 read
             because chipsets cannot guarantee that STPCLK# signal