Re: [PATCH 3/3] tracing: Rewrite filter logic to be simpler and faster

From: Steven Rostedt
Date: Mon Mar 12 2018 - 19:52:58 EST


On Mon, 12 Mar 2018 19:54:14 +0100
Jiri Olsa <jolsa@xxxxxxxxxx> wrote:

> On Mon, Mar 12, 2018 at 02:40:01PM -0400, Steven Rostedt wrote:
> > On Mon, 12 Mar 2018 16:10:17 +0100
> > Jiri Olsa <jolsa@xxxxxxxxxx> wrote:
> >
> > > got it crashed when clearing the filter via 'echo > filter'
> >
> > Awesome. I'll go and test this out. Thanks!
> >
> > Hmm, could you pull my tree and test my branch: ftrace/core. I may have
> > already fixed this but haven't posted the latest (which I'll do before
> > pushing to next).
>
> I couldn't apply your patches from mailbox so I used your ftrace/core already
>

Jiri, If you apply the below, does it fix it for you?

-- Steve

diff --git a/kernel/trace/trace_events_filter.c b/kernel/trace/trace_events_filter.c
index a5a131ec3c9c..4099e141188c 100644
--- a/kernel/trace/trace_events_filter.c
+++ b/kernel/trace/trace_events_filter.c
@@ -1498,11 +1498,14 @@ static int process_preds(struct trace_event_call *call,
return ret;
}

- prog = predicate_parse(filter_string, nr_parens, nr_preds,
+ if (!nr_preds) {
+ prog = NULL;
+ } else {
+ prog = predicate_parse(filter_string, nr_parens, nr_preds,
parse_pred, call, pe);
- if (IS_ERR(prog))
- return PTR_ERR(prog);
-
+ if (IS_ERR(prog))
+ return PTR_ERR(prog);
+ }
rcu_assign_pointer(filter->prog, prog);
return 0;
}