n-api: reduce gc finalization stress

https://github.com/nodejs/node/pull/24494 fixed a crash
but resulted in increased stress on gc finalization. A leak
was reported in https://github.com/nodejs/node/issues/26667 which
we are still investigating. As part of this investigation I
realized we can optimize to reduce amount of deferred finalization.
Regardless of the root cause of the leak this should be a
good optimization. It also resolves the leak for the case being
reported in #26667. The OP in 26667 has confirmed that he can
still recreate the original problem that 24494 fixed and that
the fix still works with this optimization

PR-URL: https://github.com/nodejs/node/pull/27085
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

1 files changed, 9 insertions, 7 deletions

diff --git a/src/js_native_api_v8.cc b/src/js_native_api_v8.cc
index f6914e72dd..134ae992ec 100644
--- a/src/js_native_api_v8.cc
+++ b/src/js_native_api_v8.cc
@@ -227,10 +227,11 @@ class Reference : private Finalizer {
   // from one of Unwrap or napi_delete_reference.
   //
   // When it is called from Unwrap or napi_delete_reference we only
-  // want to do the delete if the finalizer has already run,
+  // want to do the delete if the finalizer has already run or
+  // cannot have been queued to run (ie the reference count is > 0),
   // otherwise we may crash when the finalizer does run.
-  // If the finalizer has not already run delay the delete until
-  // the finalizer runs by not doing the delete
+  // If the finalizer may have been queued and has not already run
+  // delay the delete until the finalizer runs by not doing the delete
   // and setting _delete_self to true so that the finalizer will
   // delete it when it runs.
   //
@@ -238,13 +239,14 @@ class Reference : private Finalizer {
   // the finalizer and _delete_self is set. In this case we
   // know we need to do the deletion so just do it.
   static void Delete(Reference* reference) {
-    if ((reference->_delete_self) || (reference->_finalize_ran)) {
+    if ((reference->RefCount() != 0) ||
+        (reference->_delete_self) ||
+        (reference->_finalize_ran)) {
       delete reference;
     } else {
-      // reduce the reference count to 0 and defer until
-      // finalizer runs
+      // defer until finalizer runs as
+      // it may alread be queued
       reference->_delete_self = true;
-      while (reference->Unref() != 0) {}
     }
   }