Re: [PATCH 01/18] tracing: Add function based events

Jiri Olsa
2018-02-07T12:06:51Z

On Tue, Feb 06, 2018 at 10:09:17PM -0500, Steven Rostedt wrote:
> On Mon, 5 Feb 2018 10:00:50 -0500
> Steven Rostedt <rostedt@goodmis.org> wrote:
>
> > On Mon, 5 Feb 2018 09:24:23 +0100
> > Jiri Olsa <jolsa@redhat.com> wrote:
> >
> >
> > > should this be done under 'func_event_mutex' ?
> >
> > Probably.
>
> I think we only need to add the list.

yep, seems enough

jirka

>
> >
> > >
> > > I tried and crashed the system by running 2 scripts with:
> > >
> > > echo 'ip_rcv(u64 skb, u64 dev)' > /sys/kernel/debug/tracing/function_events
> > > echo 'SyS_openat(int dfd, string buf, x32 flags, x32 mode)' >> /sys/kernel/debug/tracing/function_events
> > > echo 'SyS_open(x8[32] buf, x32 flags, x32 mode)' >> /sys/kernel/debug/tracing/function_events
> > >
> >
>
> There's no reason that we can't have more than one function event
> attached to the same function. I'm adding this:
>
> diff --git a/kernel/trace/trace_event_ftrace.c b/kernel/trace/trace_event_ftrace.c
> index b145639eac45..928168fc2025 100644
> --- a/kernel/trace/trace_event_ftrace.c
> +++ b/kernel/trace/trace_event_ftrace.c
> @@ -1275,12 +1275,6 @@ static int create_function_event(int argc, char **argv)
> if (state != FUNC_STATE_END)
> goto fail;
>
> - ret = -EALREADY;
> - list_for_each_entry(fe, &func_events, list) {
> - if (strcmp(fe->func, func_event->func) == 0)
> - goto fail;
> - }
> -
> ret = ftrace_set_filter(&func_event->ops, func_event->func,
> strlen(func_event->func), 0);
> if (ret < 0)
> @@ -1290,7 +1284,9 @@ static int create_function_event(int argc, char **argv)
> if (ret < 0)
> goto fail;
>
> + mutex_lock(&func_event_mutex);
> list_add_tail(&func_event->list, &func_events);
> + mutex_unlock(&func_event_mutex);
> return 0;
> fail:
> free_func_event(func_event);
>
> -- Steve