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, 10 insertions, 0 deletions

diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig
index 16e5bb5daaa5..d7b2de744631 100644
--- a/kernel/trace/Kconfig
+++ b/kernel/trace/Kconfig
@@ -101,6 +101,16 @@ config SCHED_TRACER
           This tracer tracks the latency of the highest priority task
           to be scheduled in, starting from the point it has woken up.
 
+config NOP_TRACER
+        bool "NOP Tracer"
+        depends on HAVE_FTRACE
+        depends on DEBUG_KERNEL
+        select TRACING
+        help
+          This tracer does nothing. The primary purpose for it is to
+          politely print the output of ftrace_printk() calls without
+          the overhead of an irrelevant trace taking place.
+
 config CONTEXT_SWITCH_TRACER
         bool "Trace process context switches"
         depends on HAVE_FTRACE