linux-kernel - Re: about use wild cards for set_ftrace

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Date:	Thu, 27 Nov 2008 16:58:06 +0100
From:	"Frédéric Weisbecker" <fweisbec@...il.com>
To:	walimis <walimisdev@...il.com>
Cc:	"Steven Rostedt" <rostedt@...dmis.org>,
	linux-kernel@...r.kernel.org, "Ingo Molnar" <mingo@...e.hu>
Subject: Re: about use wild cards for set_ftrace_filter and so on

2008/11/27 walimis <walimisdev@...il.com>:
> On Thu, Nov 27, 2008 at 10:34:19AM -0500, Steven Rostedt wrote:
>>
>>On Thu, 27 Nov 2008, walimis wrote:
>>
>>>
>>> I encountered an issue when using ftrace.
>>> We know that we can use wild cards to set set_ftrace_filter, but there's
>>> problem when using 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 files' name to set_ftrace_filter, not "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 enclose 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.
>>> I suppose that we can add some notes to document, so a patch attached.
>>
>>Using TB? It's best to inline the patch, that way I can comment on it
>>better.
> Using mutt, but I don't know how to inline the patch now.
>
>>
>>Anyway, you should fix the example. I also recommend a single quote over
>>double, to prevent any other translation that bash might do.
>>
>>The example in ftrace.txt should be:
>>
>> # echo 'hrtimer_*' > /debug/tracing/set_ftrace_filter
>>
>>
>>Thanks,
>>
>>-- Steve
>>
>>/me goes back to eating turkeys.
> I only add a note, but I wonder whether enough.
> If needed, I can add a example to this document.
>
> Impact: imporve document
>
> Signed-off-by: walimis <walimisdev@...il.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


Cc'ed Ingo.
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