[PATCH v2] tracing: Add WARN_ON_ONCE when returned value is negative

[Hyeonggon Yoo <42.hyeyoo@gmail.com>]

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.

Signed-off-by: Hyeonggon Yoo <42.hyeyoo@gmail.com>
---
 kernel/trace/trace_events_hist.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
index c1abd63f1d6c..d169946ea4e9 100644
--- 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);
 	}
 }
 
-- 
2.25.1