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

commit 854145e0a8e9a05f7366d240e2f99d9c1ca6d6dd upstream.

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
Fixes: 85f2b08268c01 ("tracing: Add basic event trigger framework")
Signed-off-by: Chunyu Hu <chuhu@redhat.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index bb1ac9cbe30afff8310a9ba4d6aa21c5fabbed30..a8bd1ca97e0307fb6a91b636531d5fd621b22230 100644 (file)
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -1546,8 +1546,13 @@ event_create_dir(struct dentry *parent, struct ftrace_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);