ftrace: disable tracing on acpi idle calls

The acpi idle waits calls local_irq_save and then uses mwait to go into
idle. The tracer gets reenabled at local_irq_save but does not detect that
the idle allows for wake ups.

This patch adds code to disable the tracing when acpi puts the CPU to idle.

Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

drivers/acpi/processor_idle.c

@@ -272,6 +272,8 @@ static atomic_t c3_cpu_count;
 /* Common C-state entry for C2, C3, .. */
 static void acpi_cstate_enter(struct acpi_processor_cx *cstate)
 {
+	/* Don't trace irqs off for idle */
+	stop_critical_timings();
 	if (cstate->entry_method == ACPI_CSTATE_FFH) {
 		/* Call into architectural FFH based C-state */
 		acpi_processor_ffh_cstate_enter(cstate);
@@ -284,6 +286,7 @@ static void acpi_cstate_enter(struct acpi_processor_cx *cstate)
 		   gets asserted in time to freeze execution properly. */
 		unused = inl(acpi_gbl_FADT.xpm_timer_block.address);
 	}
+	start_critical_timings();
 }
 #endif /* !CONFIG_CPU_IDLE */
 
@@ -1418,6 +1421,8 @@ static inline void acpi_idle_update_bm_rld(struct acpi_processor *pr,
  */
 static inline void acpi_idle_do_entry(struct acpi_processor_cx *cx)
 {
+	/* Don't trace irqs off for idle */
+	stop_critical_timings();
 	if (cx->entry_method == ACPI_CSTATE_FFH) {
 		/* Call into architectural FFH based C-state */
 		acpi_processor_ffh_cstate_enter(cx);
@@ -1432,6 +1437,7 @@ static inline void acpi_idle_do_entry(struct acpi_processor_cx *cx)
 		   gets asserted in time to freeze execution properly. */
 		unused = inl(acpi_gbl_FADT.xpm_timer_block.address);
 	}
+	start_critical_timings();
 }
 
 /**