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>
1 file changed