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SubjectRe: [PATCH] tracing: Restore system filter behavior
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On Wed, 2011-11-02 at 14:51 -0400, Steven Rostedt wrote:
> On Wed, 2011-11-02 at 14:22 -0400, Steven Rostedt wrote:
>
> > The above shows how things are just ambiguous. I have no problem in
> > using the top filter to set multiple events. But the top filter should
> > not keep the state of what was set. Perhaps just have system event
> > filters always show default text. Like:
> >
> > # cat /debug/tracing/events/sched/filter
> > ### global filter ###
> > # Use this to set multiple event filters
> > # Only affects events that have the event fields specified in the filter
> >
> >
> > I'll add your patch, but are you OK with the above always printing for
> > system event filters? Just to remove the ambiguous state.
>
>
> As the filter is also used to show errors, I'll only have it print the
> "message" if the filter worked. If there's an error, then the error
> message will display instead.
>

What's your thought on the below patch?

-- Steve

diff --git a/kernel/trace/trace_events_filter.c b/kernel/trace/trace_events_filter.c
index 86040d9..6dee2b5 100644
--- a/kernel/trace/trace_events_filter.c
+++ b/kernel/trace/trace_events_filter.c
@@ -27,6 +27,12 @@
#include "trace.h"
#include "trace_output.h"

+#define DEFAULT_SYS_FILTER_MESSAGE \
+ "### global filter ###\n" \
+ "# Use this to set filters for multiple events.\n" \
+ "# Only events with the given fields will be affected.\n" \
+ "# If no events are modified, an error message will be displayed here"
+
enum filter_op_ids
{
OP_OR,
@@ -646,7 +652,7 @@ void print_subsystem_event_filter(struct event_subsystem *system,
if (filter && filter->filter_string)
trace_seq_printf(s, "%s\n", filter->filter_string);
else
- trace_seq_printf(s, "none\n");
+ trace_seq_printf(s, DEFAULT_SYS_FILTER_MESSAGE "\n");
mutex_unlock(&event_mutex);
}

@@ -1838,7 +1844,8 @@ int apply_subsystem_event_filter(struct event_subsystem *system,
if (!filter)
goto out;

- replace_filter_string(filter, filter_string);
+ /* System filters just show a default message */
+ replace_filter_string(filter, DEFAULT_SYS_FILTER_MESSAGE);
/*
* No event actually uses the system filter
* we can free it without synchronize_sched().
@@ -1848,14 +1855,12 @@ int apply_subsystem_event_filter(struct event_subsystem *system,

parse_init(ps, filter_ops, filter_string);
err = filter_parse(ps);
- if (err) {
- append_filter_err(ps, system->filter);
- goto out;
- }
+ if (err)
+ goto err_filter;

err = replace_system_preds(system, ps, filter_string);
if (err)
- append_filter_err(ps, system->filter);
+ goto err_filter;

out:
filter_opstack_clear(ps);
@@ -1865,6 +1870,11 @@ out_unlock:
mutex_unlock(&event_mutex);

return err;
+
+err_filter:
+ replace_filter_string(filter, filter_string);
+ append_filter_err(ps, system->filter);
+ goto out;
}

#ifdef CONFIG_PERF_EVENTS



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