linux-kernel - Re: [patch] trace: find the correct ftrace event

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Date:	Sat, 20 Mar 2010 09:37:13 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Dan Carpenter <error27@...il.com>
Cc:	Ingo Molnar <mingo@...hat.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Li Zefan <lizf@...fujitsu.com>,
	Tom Zanussi <tzanussi@...il.com>, linux-kernel@...r.kernel.org,
	kernel-janitors@...r.kernel.org
Subject: Re: [patch] trace: find the correct ftrace event

On Sat, 2010-03-20 at 16:19 +0300, Dan Carpenter wrote:
> The original code doesn't work because "call" is never NULL there.

A one line change would have done the same ;-)

> Signed-off-by: Dan Carpenter <error27@...il.com>
> ---
> My code should work, but it seems like there should but it seems like
> there should be a more elegant way to do this?
> 
> diff --git a/kernel/trace/trace_events_filter.c b/kernel/trace/trace_events_filter.c
> index 4615f62..6070c70 100644
> --- a/kernel/trace/trace_events_filter.c
> +++ b/kernel/trace/trace_events_filter.c
> @@ -1388,16 +1388,19 @@ int ftrace_profile_set_filter(struct perf_event *event, int event_id,
>  	struct event_filter *filter;
>  	struct filter_parse_state *ps;
>  	struct ftrace_event_call *call = NULL;
> +	int found = 0;
>  
>  	mutex_lock(&event_mutex);
>  
>  	list_for_each_entry(call, &ftrace_events, list) {
> -		if (call->id == event_id)
> +		if (call->id == event_id) {
> +			found = 1;
>  			break;
> +		}
>  	}
>  
>  	err = -EINVAL;
> -	if (!call)

	if (call == &ftrace_events)

-- Steve

> +	if (!found)
>  		goto out_unlock;
>  
>  	err = -EEXIST;


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