8350889: GenShen: Break out of infinite loop of old GC cycles

Reviewed-by: wkemper, ysr

Author: kdnilsen

src/hotspot/share/gc/shenandoah/heuristics/shenandoahAdaptiveHeuristics.cpp

@@ -241,6 +241,7 @@ bool ShenandoahAdaptiveHeuristics::should_start_gc() {
                 ", allocated: %zu", available, capacity, allocated);
 
   if (_start_gc_is_pending) {
+    log_trigger("GC start is already pending");
     return true;
   }
 

src/hotspot/share/gc/shenandoah/shenandoahRegulatorThread.cpp

@@ -74,6 +74,7 @@ void ShenandoahRegulatorThread::regulate_young_and_old_cycles() {
           if (start_old_cycle()) {
             log_debug(gc)("Heuristics request for old collection accepted");
             _young_heuristics->cancel_trigger_request();
+            _old_heuristics->cancel_trigger_request();
           } else if (request_concurrent_gc(YOUNG)) {
             log_debug(gc)("Heuristics request for young collection accepted");
             _young_heuristics->cancel_trigger_request();