linux-kernel - Re: [PATCH 2/3] tracing/ftrace: fix the check of ftrace_trace

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Date:	Thu, 4 Dec 2008 18:18:14 -0500 (EST)
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Frederic Weisbecker <fweisbec@...il.com>
cc:	Ingo Molnar <mingo@...e.hu>,
	Linux Kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/3] tracing/ftrace: fix the check of ftrace_trace_task


On Thu, 4 Dec 2008, Frederic Weisbecker wrote:

> Impact: fix default empty traces on function-graph-tracer
> 
> The actual ftrace_trace_task() checks if ftrace_pid_trace is allocated
> and return 1 if it is true.
> If it is NULL, it will check the bit of pid tracing flag for the current
> task (which are not set by default).
> So by default, a task is not traced.
> Actually all tasks should be traced by default and filter_by_pid when
> ftrace_pid_trace is allocated.

Heh, I thought my output look funny. The function tracer does not use it 
since it registers a different function. But because the graph tracer
only shows the current task on switch (I did not look into trace options)
I could not really test it well.

-- Steve

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

> 
> The appropriate condition should be to return 1 if filter_by_pid is
> set.
> 
> Cc: Steven Rostedt <rostedt@...dmis.org>
> Signed-off-by: Frederic Weisbecker <fweisbec@...il.com>
> ---
>  kernel/trace/trace.h |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
> 
> diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
> index a71bbe0..5ac6970 100644
> --- a/kernel/trace/trace.h
> +++ b/kernel/trace/trace.h
> @@ -551,7 +551,7 @@ extern struct pid *ftrace_pid_trace;
>  
>  static inline int ftrace_trace_task(struct task_struct *task)
>  {
> -	if (ftrace_pid_trace)
> +	if (!ftrace_pid_trace)
>  		return 1;
>  
>  	return test_tsk_trace_trace(task);
> -- 
> 1.5.6.3
> 
> 
> 
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