linux-kernel - Re: [PATCH] tracing/ftrace: fix the check on nopped sites

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Message-ID: <alpine.DEB.2.00.0903161808530.5094@gandalf.stny.rr.com>
Date:	Mon, 16 Mar 2009 18:09:37 -0400 (EDT)
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Frederic Weisbecker <fweisbec@...il.com>
cc:	Ingo Molnar <mingo@...e.hu>, linux-kernel@...r.kernel.org,
	Zhaolei <zhaolei@...fujitsu.com>
Subject: Re: [PATCH] tracing/ftrace: fix the check on nopped sites



On Mon, 16 Mar 2009, Frederic Weisbecker wrote:

> Impact: fix a dynamic tracing failure
> 
> Recently, the function and function graph tracers failed to use dynamic
> tracing after the following commit:
> 
> fa9d13cf135efbd454453a53b6299976bea245a9
> (ftrace: don't try to __ftrace_replace_code on !FTRACE_FL_CONVERTED rec)
> 
> The patch is right except a mistake on the check for the FTRACE_FL_CONVERTED
> flag. The code patching is aborted in case of successfully nopped sites.
> What we want is the opposite: ignore the callsites that haven't been nopped.
> 
> Signed-off-by: Frederic Weisbecker <fweisbec@...il.com>
> ---
>  kernel/trace/ftrace.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
> 
> diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
> index 90d5729..7847806 100644
> --- a/kernel/trace/ftrace.c
> +++ b/kernel/trace/ftrace.c
> @@ -537,7 +537,7 @@ static void ftrace_replace_code(int enable)
>  		 */
>  		if (rec->flags & FTRACE_FL_FREE ||
>  		    rec->flags & FTRACE_FL_FAILED ||
> -		    rec->flags & FTRACE_FL_CONVERTED)
> +		    !(rec->flags & FTRACE_FL_CONVERTED))
>  			continue;
>  
>  		/* ignore updates to this record's mcount site */
> -- 

Heh, I just found this bug too, and wrote a patch. But you posted before I 
did, so I'll let you have it ;-)

Acked-by: Steven Rostedt <srostedt@...hat.com>

-- Steve

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