linux-kernel - [PATCH 3.16.y-ckt 042/142] tracing: Fix showing function event in available

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Message-Id: <1458643271-4227-43-git-send-email-luis.henriques@canonical.com>
Date:	Tue, 22 Mar 2016 10:39:31 +0000
From:	Luis Henriques <luis.henriques@...onical.com>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com
Cc:	Steven Rostedt <rostedt@...dmis.org>,
	Luis Henriques <luis.henriques@...onical.com>
Subject: [PATCH 3.16.y-ckt 042/142] tracing: Fix showing function event in available_events

3.16.7-ckt26 -stable review patch.  If anyone has any objections, please let me know.

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

From: "Steven Rostedt (Red Hat)" <rostedt@...dmis.org>

commit d045437a169f899dfb0f6f7ede24cc042543ced9 upstream.

The ftrace:function event is only displayed for parsing the function tracer
data. It is not used to enable function tracing, and does not include an
"enable" file in its event directory.

Originally, this event was kept separate from other events because it did
not have a ->reg parameter. But perf added a "reg" parameter for its use
which caused issues, because it made the event available to functions where
it was not compatible for.

Commit 9b63776fa3ca9 "tracing: Do not enable function event with enable"
added a TRACE_EVENT_FL_IGNORE_ENABLE flag that prevented the function event
from being enabled by normal trace events. But this commit missed keeping
the function event from being displayed by the "available_events" directory,
which is used to show what events can be enabled by set_event.

One documented way to enable all events is to:

 cat available_events > set_event

But because the function event is displayed in the available_events, this
now causes an INVALID error:

 cat: write error: Invalid argument

Reported-by: Chunyu Hu <chuhu@...hat.com>
Fixes: 9b63776fa3ca9 "tracing: Do not enable function event with enable"
Signed-off-by: Steven Rostedt <rostedt@...dmis.org>
Signed-off-by: Luis Henriques <luis.henriques@...onical.com>
---
 kernel/trace/trace_events.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index 41c56b7e882c..ecf3e9fb8ee4 100644
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -642,7 +642,8 @@ t_next(struct seq_file *m, void *v, loff_t *pos)
 		 * The ftrace subsystem is for showing formats only.
 		 * They can not be enabled or disabled via the event files.
 		 */
-		if (call->class && call->class->reg)
+		if (call->class && call->class->reg &&
+		    !(call->flags & TRACE_EVENT_FL_IGNORE_ENABLE))
 			return file;
 	}