tracing: Add WARN_ON_ONCE when returned value is negative

ret is assigned return value of event_hist_trigger_func, but the value
is unused. It is better to warn when returned value is negative,
rather than just ignoring it.

Link: https://lkml.kernel.org/r/20210529061423.GA103954@hyeyoo
Signed-off-by: Hyeonggon Yoo <42.hyeyoo@gmail.com>
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 dacd6fe0f60c97a8b91015083cd0e819c3e7c150..ba03b7d84fc2bddb989c11567843a799795dbe55 100644 (file)
--- a/kernel/trace/trace_events_hist.c
+++ b/kernel/trace/trace_events_hist.c
@@ -5232,6 +5232,7 @@ static void unregister_field_var_hists(struct hist_trigger_data *hist_data)
                cmd = hist_data->field_var_hists[i]->cmd;
                ret = event_hist_trigger_func(&trigger_hist_cmd, file,
                                              "!hist", "hist", cmd);
+               WARN_ON_ONCE(ret < 0);
        }
 }