Impact: imporve document

Signed-off-by: walimis <walimisdev@gmail.com>
---
 Documentation/ftrace.txt |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)

diff --git a/Documentation/ftrace.txt b/Documentation/ftrace.txt
index de05042..9735434 100644
--- a/Documentation/ftrace.txt
+++ b/Documentation/ftrace.txt
@@ -1251,6 +1251,9 @@ These are the only wild cards which are supported.
 
   <match>*<match> will not work.
 
+Note: you'd better to use "" to enclose wild cards, otherwise in some
+case you can't get the correct result.
+
  # echo hrtimer_* > /debug/tracing/set_ftrace_filter
 
 Produces:
-- 
1.6.0.3