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

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Date:	Sat, 20 Mar 2010 10:07:16 -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 16:56 +0300, Dan Carpenter wrote:

> > > 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)
> > 
> 
> Man...  That makes my head hurt.  It only works because ->list is the 
> first element in the struct.
> 
> We'd need a cast.

Oops, I missed the fact that it was list_*_entry(). That should be:

	if (call->list != &ftrace_events)

No cast needed.

> 
> Is that really cleaner?

Perhaps not, but I think it is more elegant ;-)

-- Steve


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