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SubjectRe: [PATCH 1/1] ftrace: improve document

* Steven Rostedt <rostedt@goodmis.org> wrote:

>
> On Fri, 28 Nov 2008, walimis wrote:
> >
> > Signed-off-by: walimis <walimisdev@gmail.com>
> > Reviewed-by: Ingo Molnar <mingo@elte.hu>
> > Reviewed-by: Steven Rostedt <srostedt@redhat.com>
>
> Acked-by: Steven Rostedt <srostedt@redhat.com>

applied it to tip/tracing/ftrace, thanks guys! (Changed the commit log a
bit, see the final commit below.)

Ingo

-------------->
From c072c24975ec4f0ccfcb6f5c8a8040b6eb75ef8f Mon Sep 17 00:00:00 2001
From: walimis <walimisdev@gmail.com>
Date: Fri, 28 Nov 2008 12:21:19 +0800
Subject: [PATCH] ftrace: improve documentation

Impact: extend documentation with notice of using wild cards correctly

We know that we can use wild cards to set set_ftrace_filter, but there's
problem when using them naively such as:

echo h* > /debug/tracing/set_ftrace_filter

If there are files named with "h" prefix in current directory,
echo "h*" will echo these filenames to set_ftrace_filter, not the
intended "h*".

For example:

$ cat /debug/tracing/available_filter_functions |grep ^hr |wc -l
23
$ ls
$ touch hraa hrdd
$ ls
hraa hrdd
$ echo hr* > /debug/tracing/set_ftrace_filter
$ cat /debug/tracing/set_ftrace_filter

No output in /debug/tracing/set_ftrace_filter!

If we use '' to escape wild cards, it works:

$ ls
hraa hrdd
$ echo "hr*" > /debug/tracing/set_ftrace_filter
$ cat /debug/tracing/set_ftrace_filter |wc -l
23

This problem can lead to unexpected result if current directory has a
lot of files.

Signed-off-by: walimis <walimisdev@gmail.com>
Acked-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
---
Documentation/ftrace.txt | 8 ++++++--
1 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/Documentation/ftrace.txt b/Documentation/ftrace.txt
index de05042..803b131 100644
--- a/Documentation/ftrace.txt
+++ b/Documentation/ftrace.txt
@@ -1251,7 +1251,11 @@ These are the only wild cards which are supported.

<match>*<match> will not work.

- # echo hrtimer_* > /debug/tracing/set_ftrace_filter
+Note: It is better to use quotes to enclose the wild cards, otherwise
+ the shell may expand the parameters into names of files in the local
+ directory.
+
+ # echo 'hrtimer_*' > /debug/tracing/set_ftrace_filter

Produces:

@@ -1306,7 +1310,7 @@ Again, now we want to append.
# echo sys_nanosleep > /debug/tracing/set_ftrace_filter
# cat /debug/tracing/set_ftrace_filter
sys_nanosleep
- # echo hrtimer_* >> /debug/tracing/set_ftrace_filter
+ # echo 'hrtimer_*' >> /debug/tracing/set_ftrace_filter
# cat /debug/tracing/set_ftrace_filter
hrtimer_run_queues
hrtimer_run_pending

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