linux-kernel - Re: [PATCH 09/10] tracing/filter: Change filter_match_preds function to use walk_pred

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Date:	Wed, 10 Aug 2011 17:16:32 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Jiri Olsa <jolsa@...hat.com>
Cc:	fweisbec@...il.com, mingo@...hat.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 09/10] tracing/filter: Change filter_match_preds
 function to use walk_pred_tree

On Wed, 2011-08-10 at 17:14 -0400, Steven Rostedt wrote:
> On Thu, 2011-08-04 at 12:08 +0200, Jiri Olsa wrote:
> > Changing filter_match_preds function to use unified predicates tree
> > processing.
> > 
> > Signed-off-by: Jiri Olsa <jolsa@...hat.com>
> > ---
> >  kernel/trace/trace_events_filter.c |  119 +++++++++++++++++-------------------
> >  1 files changed, 55 insertions(+), 64 deletions(-)
> > 
> > diff --git a/kernel/trace/trace_events_filter.c b/kernel/trace/trace_events_filter.c
> > index d4e0c09..55b13b9 100644
> > --- a/kernel/trace/trace_events_filter.c
> > +++ b/kernel/trace/trace_events_filter.c
> > @@ -467,6 +467,7 @@ static int process_ops(struct filter_pred *preds,
> >  
> >  	for (i = 0; i < op->val; i++) {
> >  		pred = &preds[op->ops[i]];
> > +		BUG_ON(!pred->fn);
> 
> Why the added BUG_ON()s? Do we really need to crash the kernel on error
> here?

I mean, could be instead have:

	if (!WARN_ON_ONCE(!pred->fn))
> >  		match = pred->fn(pred, rec);


> >  		if (!!match == type)
> >  			return match;
> > @@ -474,92 +475,82 @@ static int process_ops(struct filter_pred *preds,
> >  	return match;
> >  }
> >  
> > +struct filter_match_preds_data {
> > +	struct filter_pred *preds;
> > +	int match;
> > +	void *rec;
> > +};
> > +
> > +static int filter_match_preds_cb(enum move_type move, struct filter_pred *pred,
> > +				 int *err, void *data)
> > +{
> > +	struct filter_match_preds_data *d = data;
> > +
> > +	*err = 0;
> > +	switch (move) {
> > +	case MOVE_DOWN:
> > +		/* only AND and OR have children */
> > +		if (pred->left != FILTER_PRED_INVALID) {
> > +			/* If ops is set, then it was folded. */
> > +			if (!pred->ops)
> > +				return WALK_PRED_DEFAULT;
> > +			/* We can treat folded ops as a leaf node */
> > +			d->match = process_ops(d->preds, pred, d->rec);
> > +		} else {
> > +			BUG_ON(!pred->fn);

			if (!WARN_ON_ONCE(!pred->fn))
> > +			d->match = pred->fn(pred, d->rec);

-- Steve

> > +		}
> 


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