tracing: Return -ENOENT if there is no target synthetic event

Return -ENOENT error if there is no target synthetic event.
This notices an operation failure to user as below;

  # echo 'wakeup_latency u64 lat; pid_t pid;' > synthetic_events
  # echo '!wakeup' >> synthetic_events
  sh: write error: No such file or directory

Link: http://lkml.kernel.org/r/154013449986.25576.9487131386597290172.stgit@devbox
Acked-by: Tom Zanussi <zanussi@linux.intel.com>
Tested-by: Tom Zanussi <zanussi@linux.intel.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Rajvi Jingar <rajvi.jingar@intel.com>
Cc: stable@vger.kernel.org
Fixes: 4b147936fa50 ('tracing: Add support for 'synthetic' events')
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
index d239004aaf29052eec50aaf61772c2b0de7c7947..eb908ef2ececf336fc2ed8996439005a32f5afc9 100644 (file)
--- a/kernel/trace/trace_events_hist.c
+++ b/kernel/trace/trace_events_hist.c
@@ -1063,8 +1063,10 @@ static int create_synth_event(int argc, char **argv)
                event = NULL;
                ret = -EEXIST;
                goto out;
-       } else if (delete_event)
+       } else if (delete_event) {
+               ret = -ENOENT;
                goto out;
+       }
 
        if (argc < 2) {
                ret = -EINVAL;