On Tue, 26 Sep 2023 10:20:58 -0400
Nicholas Lowell <nicholas.low...@gmail.com> wrote:
> From: Nicholas Lowell <nlow...@lexmark.com>
>
> If there are no filters in the event subsystem, then there's no
> reason to continue and hit the potentially time consuming
> tracepoint_synchronize_unregister function. This should give
> a speed up for initial disabling/configuring
>
> Signed-off-by: Nicholas Lowell <nlow...@lexmark.com>
> ---
> kernel/trace/trace_events_filter.c | 19 ++++++++++++++-----
> 1 file changed, 14 insertions(+), 5 deletions(-)
>
> diff --git a/kernel/trace/trace_events_filter.c
> b/kernel/trace/trace_events_filter.c
> index 33264e510d16..93653d37a132 100644
> --- a/kernel/trace/trace_events_filter.c
> +++ b/kernel/trace/trace_events_filter.c
> @@ -1317,22 +1317,29 @@ void free_event_filter(struct event_filter *filter)
> __free_filter(filter);
> }
>
> -static inline void __remove_filter(struct trace_event_file *file)
> +static inline int __remove_filter(struct trace_event_file *file)
> {
> filter_disable(file);
> - remove_filter_string(file->filter);
> + if (file->filter)
> + remove_filter_string(file->filter);
> + else
> + return 0;
> +
> + return 1;
The above looks awkward. What about:
if (!file->filter)
return 0;
remove_filter_string(file->filter);
return 1;
?
Or better yet:
if (!file->filter)
return false;
remove_filter_string(file->filter);
return true;
and ...
> }
>
> -static void filter_free_subsystem_preds(struct trace_subsystem_dir *dir,
> +static int filter_free_subsystem_preds(struct trace_subsystem_dir *dir,
> struct trace_array *tr)
> {
> struct trace_event_file *file;
> + int i = 0;
We don't really need a counter. It's either do the synchronization or
we don't.
bool do_sync = false;
>
> list_for_each_entry(file, &tr->events, list) {
> if (file->system != dir)
> continue;
> - __remove_filter(file);
> + i += __remove_filter(file);
if (remove_filter(file))
do_sync = true;
> }
return do_sync;
> + return i;
> }
>
> static inline void __free_subsystem_filter(struct trace_event_file *file)
> @@ -2411,7 +2418,9 @@ int apply_subsystem_event_filter(struct
> trace_subsystem_dir *dir,
> }
>
> if (!strcmp(strstrip(filter_string), "0")) {
> - filter_free_subsystem_preds(dir, tr);
> + if (filter_free_subsystem_preds(dir, tr) == 0)
> + goto out_unlock;
> +
/* If nothing was freed, we do not need to sync */
if (!filter_free_subsystem_preds(dir, tr))
goto out_unlock;
And yes, add the comment.
And actually, in that block with the goto out_unlock, we should have:
if (!filter_free_subsystem_preds(dir, tr)) {
if (!(WARN_ON_ONCE(system->filter))
goto out_unlock;
}
If there were no preds, ideally there would be no subsystem filter. But
if that's not the case, we need to warn about that and then continue.
-- Steve
> remove_filter_string(system->filter);
> filter = system->filter;
> system->filter = NULL;
