[PATCH] kernel-shark: Handle traces with sched_switch and no sched_waking

[John Keeping <john@xxxxxxxxxxxx>]

plugin_sched_init_context() is careful to make the sched_waking (or
sched_wakeup{,_new}) event optional but the initializer blindly
dereferences plugin_ctx->sched_waking_event which is null if no waking
event is found.

Add the necessary checks to avoid segfaults when (de)initializing the
plugin.

Signed-off-by: John Keeping <john@xxxxxxxxxxxx>
---
 src/plugins/sched_events.c | 16 ++++++++++------
 1 file changed, 10 insertions(+), 6 deletions(-)

diff --git a/src/plugins/sched_events.c b/src/plugins/sched_events.c
index 83c2520..198ed49 100644
--- a/src/plugins/sched_events.c
+++ b/src/plugins/sched_events.c
@@ -193,9 +193,11 @@ int KSHARK_PLOT_PLUGIN_INITIALIZER(struct kshark_data_stream *stream)
 				      plugin_ctx->sched_switch_event->id,
 				      plugin_sched_swith_action);
 
-	kshark_register_event_handler(stream,
-				      plugin_ctx->sched_waking_event->id,
-				      plugin_sched_wakeup_action);
+	if (plugin_ctx->sched_waking_event) {
+		kshark_register_event_handler(stream,
+					      plugin_ctx->sched_waking_event->id,
+					      plugin_sched_wakeup_action);
+	}
 
 	kshark_register_draw_handler(stream, plugin_draw);
 
@@ -213,9 +215,11 @@ int KSHARK_PLOT_PLUGIN_DEINITIALIZER(struct kshark_data_stream *stream)
 						plugin_ctx->sched_switch_event->id,
 						plugin_sched_swith_action);
 
-		kshark_unregister_event_handler(stream,
-						plugin_ctx->sched_waking_event->id,
-						plugin_sched_wakeup_action);
+		if (plugin_ctx->sched_waking_event) {
+			kshark_unregister_event_handler(stream,
+							plugin_ctx->sched_waking_event->id,
+							plugin_sched_wakeup_action);
+		}
 
 		kshark_unregister_draw_handler(stream, plugin_draw);
 
-- 
2.33.0