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Date: Tue, 8 Dec 2009 10:48:27 +0100
From: Frederic Weisbecker <fweisbec@gmail.com>
To: Li Zefan <lizf@cn.fujitsu.com>
Cc: Ingo Molnar <mingo@elte.hu>, Steven Rostedt <rostedt@goodmis.org>,
       LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 05/13] ftrace: Call trace_parser_clear() properly
Message-ID: <20091208094825.GA5035@nowhere>
References: <4B1DC476.3030700@cn.fujitsu.com> <4B1DC4D2.3000406@cn.fujitsu.com>
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On Tue, Dec 08, 2009 at 11:15:30AM +0800, Li Zefan wrote:
> I found a weird behavior:
> 
>   # echo 'fuse:*' > set_ftrace_filter
>   bash: echo: write error: Invalid argument
>   # cat set_ftrace_filter
>   fuse_dev_fasync
>   fuse_dev_poll
>   fuse_copy_do
> 
> We should call trace_parser_clear() no matter ftrace_process_regex()
> returns 0 or -errno.
> 
> Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
> ---
>  kernel/trace/ftrace.c |    3 +--
>  1 files changed, 1 insertions(+), 2 deletions(-)
> 
> diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
> index 08a3fb5..ff8aecd 100644
> --- a/kernel/trace/ftrace.c
> +++ b/kernel/trace/ftrace.c
> @@ -2208,10 +2208,9 @@ ftrace_regex_write(struct file *file, const char __user *ubuf,
>  	    !trace_parser_cont(parser)) {
>  		ret = ftrace_process_regex(parser->buffer,
>  					   parser->idx, enable);
> +		trace_parser_clear(parser);
>  		if (ret)
>  			goto out_unlock;
> -
> -		trace_parser_clear(parser);
>  	}


I'm missing something. How that can happen. Anytime we reopen
the file, the parser is re-allocated.

I guess that happens if you open in rw mode? But not using the
example in the changelog?