linux-kernel - [PATCH 4.2.y-ckt 36/59] tracing: Don't display trigger file for events that can't be enabled

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Message-Id: <1462823777-8384-37-git-send-email-kamal@canonical.com>
Date:	Mon,  9 May 2016 12:55:54 -0700
From:	Kamal Mostafa <kamal@...onical.com>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com
Cc:	Chunyu Hu <chuhu@...hat.com>, Steven Rostedt <rostedt@...dmis.org>,
	Kamal Mostafa <kamal@...onical.com>
Subject: [PATCH 4.2.y-ckt 36/59] tracing: Don't display trigger file for events that can't be enabled

4.2.8-ckt10 -stable review patch.  If anyone has any objections, please let me know.

---8<------------------------------------------------------------

From: Chunyu Hu <chuhu@...hat.com>

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@...hat.com>
Signed-off-by: Steven Rostedt <rostedt@...dmis.org>
Signed-off-by: Kamal Mostafa <kamal@...onical.com>
---
 kernel/trace/trace_events.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index 78234df..825b5e4 100644
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -1626,8 +1626,13 @@ 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);
-- 
2.7.4