From a5b85bd1557209b4ef18a8cf07e60a1ca3132468 Mon Sep 17 00:00:00 2001
From: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Date: Thu, 9 May 2013 14:44:14 +0900
Subject: [PATCH] tracing: Don't succeed if event_enable_func did not register
anything
Return 0 instead of the number of activated ftrace function probes if
event_enable_func succeeded and return an error code if it failed or
did not register any functions. But it currently returns the number
of registered functions and if it didn't register anything, it returns 0,
but that is considered success.
This also fixes the return value. As if it succeeds, it returns the
number of functions that were enabled, which is returned back to
the user in ftrace_regex_write (the write() return code). If only
one function is enabled, then the return code of the write is one,
and this can confuse the user program in thinking it only wrote 1
byte.
Link: http://lkml.kernel.org/r/20130509054413.30398.55650.stgit@mhiramat-M0-7522
Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Tom Zanussi <tom.zanussi@intel.com>
Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
[ Rewrote change log to reflect that this fixes two bugs - SR ]
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
kernel/trace/trace_events.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index 53582e982e51..44ac83614c3d 100644
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -2061,8 +2061,11 @@ event_enable_func(struct ftrace_hash *hash,
if (ret < 0)
goto out_put;
ret = register_ftrace_function_probe(glob, ops, data);
- if (!ret)
+ if (!ret) {
+ ret = -ENOENT;
goto out_disable;
+ } else
+ ret = 0;
out:
mutex_unlock(&event_mutex);
return ret;
--
2.34.1