tracing: Don't display trigger file for events that can't be enabled

Currently register functions for events will be called
through the 'reg' field of event class directly without
any check when seting up triggers.

Triggers for events that don't support register through
debug fs (events under events/ftrace are for trace-cmd to
read event format, and most of them don't have a register
function except events/ftrace/functionx) can't be enabled
at all, and an oops will be hit when setting up trigger
for those events, so just not creating them is an easy way
to avoid the oops.

Link: http://lkml.kernel.org/r/1462275274-3911-1-git-send-email-chuhu@redhat.com
Cc: stable@vger.kernel.org # 3.14+
Fixes: 85f2b08268c01 ("tracing: Add basic event trigger framework")
Signed-off-by: Chunyu Hu <chuhu@redhat.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index 05ddc0820771eb7bc456aab9e2f0e5167ce7f023..6f965864cc029ad47f63c67f6713cb79a519599e 100644 (file)
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -2095,8 +2095,13 @@ event_create_dir(struct dentry *parent, struct trace_event_file *file)
        trace_create_file("filter", 0644, file->dir, file,
                          &ftrace_event_filter_fops);
 
-       trace_create_file("trigger", 0644, file->dir, file,
-                         &event_trigger_fops);
+       /*
+        * Only event directories that can be enabled should have
+        * triggers.
+        */
+       if (!(call->flags & TRACE_EVENT_FL_IGNORE_ENABLE))
+               trace_create_file("trigger", 0644, file->dir, file,
+                                 &event_trigger_fops);
 
        trace_create_file("format", 0444, file->dir, call,
                          &ftrace_event_format_fops);