This adds a mechanism to invalidate code that was generated in the background. The invalidation can…

runtime/vm/object.h

Index: runtime/vm/object.h
diff --git a/runtime/vm/object.h b/runtime/vm/object.h
index 014d0bb537887e90e8cc3c6e9ad1917548ce87d3..03a91ce9cd6c2b9f072a1969bc4451aa10970b81 100644
--- a/runtime/vm/object.h
+++ b/runtime/vm/object.h
@@ -2362,6 +2362,8 @@ class Function : public Object {
     return raw_ptr()->usage_counter_;
   }
   void set_usage_counter(intptr_t value) const {
+    // TODO(Srdjan): Assert that this is thread-safe, i.e., only
+    // set from mutator-thread or while at a safepoint (e.g., during marking).
     StoreNonPointer(&raw_ptr()->usage_counter_, value);
   }