linux-kernel - Re: [GIT PULL] tracing: Have filter check for balanced ops

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Date:	Mon, 22 Jun 2015 14:53:17 +0100
From:	Luis Henriques <luis.henriques@...onical.com>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Vince Weaver <vincent.weaver@...ne.edu>,
	Arnaldo Carvalho de Melo <acme@...nel.org>
Subject: Re: [GIT PULL] tracing: Have filter check for balanced ops

Hi Steven,

On Wed, Jun 17, 2015 at 08:36:38AM -0400, Steven Rostedt wrote:
...
> diff --git a/kernel/trace/trace_events_filter.c b/kernel/trace/trace_events_filter.c
> index ced69da0ff55..7f2e97ce71a7 100644
> --- a/kernel/trace/trace_events_filter.c
> +++ b/kernel/trace/trace_events_filter.c
> @@ -1369,19 +1369,26 @@ static int check_preds(struct filter_parse_state *ps)
>  {
>  	int n_normal_preds = 0, n_logical_preds = 0;
>  	struct postfix_elt *elt;
> +	int cnt = 0;
>  
>  	list_for_each_entry(elt, &ps->postfix, list) {
> -		if (elt->op == OP_NONE)
> +		if (elt->op == OP_NONE) {
> +			cnt++;
>  			continue;
> +		}
>  
>  		if (elt->op == OP_AND || elt->op == OP_OR) {
>  			n_logical_preds++;
> +			cnt--;
>  			continue;
>  		}
> +		if (elt->op != OP_NOT)
> +			cnt--;

Since the OP_NOT was introduced only with e12c09cf3087 ("tracing: Add
NOT to filtering logic"), how would stable kernels backport this fix?
Do you think that just dropping the 'if' and do the 'cnt--'
unconditionally would be ok?

Cheers,
--
Luís

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