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

rev 58162 : 8239926: Shenandoah: Shenandoah needs to mark nmethod's metadata

@@ -1445,10 +1445,19 @@
   }
 
   if (ShenandoahPacing) {
     pacer()->setup_for_mark();
   }
+
+  // Arm nmethods for concurrent marking.
+  // When a nmethod is about to be executed, we need to make sure that all its
+  // metadata are marked.
+  // The alternative is to remark thread roots at final mark pause, but it can
+  // be potential latency killer.
+  if (ShenandoahConcurrentRoots::should_do_concurrent_class_unloading()) {
+    ShenandoahCodeRoots::arm_nmethods();
+  }
 }
 
 void ShenandoahHeap::op_mark() {
   concurrent_mark()->mark_from_roots();
 }

@@ -1482,10 +1491,15 @@
   // It is critical that we
   // evacuate roots right after finishing marking, so that we don't
   // get unmarked objects in the roots.
 
   if (!cancelled_gc()) {
+    // If can not concurrently mark nmethod's metadata, we need to remark thread roots
+    if (!ShenandoahConcurrentRoots::can_do_concurrent_class_unloading()) {
+      concurrent_mark()->remark_thread_roots();
+    }
+
     concurrent_mark()->finish_mark_from_roots(/* full_gc = */ false);
 
     // Marking is completed, deactivate SATB barrier
     set_concurrent_mark_in_progress(false);
     mark_complete_marking_context();

@@ -1980,10 +1994,15 @@
         op_final_updaterefs();
         if (cancelled_gc()) {
           op_degenerated_fail();
           return;
         }
+      } else if (ShenandoahConcurrentRoots::can_do_concurrent_class_unloading()) {
+        // Disarm nmethods that armed for concurrent mark.
+        // On normal code path (non-empty Cset), it depends on update_roots() to
+        // disarm nmethods in degenerated GC.
+        ShenandoahCodeRoots::disarm_nmethods();
       }
 
       op_cleanup();
       break;