• walimis's avatar
    ftrace: improve documentation · c072c249
    walimis authored
    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: default avatarwalimis <walimisdev@gmail.com>
    Acked-by: default avatarSteven Rostedt <srostedt@redhat.com>
    Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
    c072c249
ftrace.txt 54.4 KB