tracing: Do not enable function event with enable

With the adding of function tracing event to perf, it caused a
side effect that produces the following warning when enabling all
events in ftrace:

 # echo 1 > /sys/kernel/debug/tracing/events/enable

[console]
event trace: Could not enable event function

This is because when enabling all events via the debugfs system
it ignores events that do not have a ->reg() function assigned.
This was to skip over the ftrace internal events (as they are
not TRACE_EVENTs). But as the ftrace function event now has
a ->reg() function attached to it for use with perf, it is no
longer ignored.

Worse yet, this ->reg() function is being called when it should
not be. It returns an error and causes the above warning to
be printed.

By adding a new event_call flag (TRACE_EVENT_FL_IGNORE_ENABLE)
and have all ftrace internel event structures have it set,
setting the events/enable will no longe try to incorrectly enable
the function event and does not warn.

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

1 files changed, 4 insertions, 1 deletions

diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index 079a93ae8a9..29111da1d10 100644
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -294,6 +294,9 @@ static int __ftrace_set_clr_event(const char *match, const char *sub,
 		if (!call->name || !call->class || !call->class->reg)
 			continue;
 
+		if (call->flags & TRACE_EVENT_FL_IGNORE_ENABLE)
+			continue;
+
 		if (match &&
 		    strcmp(match, call->name) != 0 &&
 		    strcmp(match, call->class->system) != 0)
@@ -1164,7 +1167,7 @@ event_create_dir(struct ftrace_event_call *call, struct dentry *d_events,
 		return -1;
 	}
 
-	if (call->class->reg)
+	if (call->class->reg && !(call->flags & TRACE_EVENT_FL_IGNORE_ENABLE))
 		trace_create_file("enable", 0644, call->dir, call,
 				  enable);