ftrace: add nop tracer

A no-op tracer which can serve two purposes:

 1. A template for development of a new tracer.
 2. A convenient way to see ftrace_printk() calls without
    an irrelevant trace making the output messy.

[ mingo@elte.hu: resolved conflicts ]
Signed-off-by: Steven Noonan <steven@uplinklabs.net>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 4 insertions, 0 deletions

diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index 42f65d0097f0..447d4b9b6391 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -339,6 +339,10 @@ extern int trace_selftest_startup_preemptirqsoff(struct tracer *trace,
 extern int trace_selftest_startup_wakeup(struct tracer *trace,
                                          struct trace_array *tr);
 #endif
+#ifdef CONFIG_NOP_TRACER
+extern int trace_selftest_startup_nop(struct tracer *trace,
+                                         struct trace_array *tr);
+#endif
 #ifdef CONFIG_CONTEXT_SWITCH_TRACER
 extern int trace_selftest_startup_sched_switch(struct tracer *trace,
                                                struct trace_array *tr);