timers: allow Immediates to be unrefed

Refactor Immediates handling to allow for them to be unrefed, similar
to setTimeout, but without extra handles.

Document the new `immediate.ref()` and `immediate.unref()` methods.

Add SetImmediateUnref on the C++ side.

Backport-PR-URL: https://github.com/nodejs/node/pull/19006
PR-URL: https://github.com/nodejs/node/pull/18139
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Franziska Hinkelmann <franziska.hinkelmann@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

1 files changed, 34 insertions, 6 deletions

diff --git a/src/env-inl.h b/src/env-inl.h
index 0328f058de..37d1cf172e 100644
--- a/src/env-inl.h
+++ b/src/env-inl.h
@@ -229,6 +229,10 @@ inline uint32_t Environment::ImmediateInfo::count() const {
   return fields_[kCount];
 }
 
+inline uint32_t Environment::ImmediateInfo::ref_count() const {
+  return fields_[kRefCount];
+}
+
 inline bool Environment::ImmediateInfo::has_outstanding() const {
   return fields_[kHasOutstanding] == 1;
 }
@@ -241,6 +245,14 @@ inline void Environment::ImmediateInfo::count_dec(uint32_t decrement) {
   fields_[kCount] = fields_[kCount] - decrement;
 }
 
+inline void Environment::ImmediateInfo::ref_count_inc(uint32_t increment) {
+  fields_[kRefCount] = fields_[kRefCount] + increment;
+}
+
+inline void Environment::ImmediateInfo::ref_count_dec(uint32_t decrement) {
+  fields_[kRefCount] = fields_[kRefCount] - decrement;
+}
+
 inline Environment::TickInfo::TickInfo(v8::Isolate* isolate)
     : fields_(isolate, kFieldsCount) {}
 
@@ -514,20 +526,36 @@ inline void Environment::set_fs_stats_field_array(double* fields) {
   fs_stats_field_array_ = fields;
 }
 
-void Environment::SetImmediate(native_immediate_callback cb,
+void Environment::CreateImmediate(native_immediate_callback cb,
                                void* data,
-                               v8::Local<v8::Object> obj) {
+                               v8::Local<v8::Object> obj,
+                               bool ref) {
   native_immediate_callbacks_.push_back({
     cb,
     data,
-    std::unique_ptr<v8::Persistent<v8::Object>>(
-        obj.IsEmpty() ? nullptr : new v8::Persistent<v8::Object>(isolate_, obj))
+    std::unique_ptr<v8::Persistent<v8::Object>>(obj.IsEmpty() ?
+        nullptr : new v8::Persistent<v8::Object>(isolate_, obj)),
+    ref
   });
-  if (immediate_info()->count() == 0)
-    ActivateImmediateCheck();
   immediate_info()->count_inc(1);
 }
 
+void Environment::SetImmediate(native_immediate_callback cb,
+                               void* data,
+                               v8::Local<v8::Object> obj) {
+  CreateImmediate(cb, data, obj, true);
+
+  if (immediate_info()->ref_count() == 0)
+    ToggleImmediateRef(true);
+  immediate_info()->ref_count_inc(1);
+}
+
+void Environment::SetUnrefImmediate(native_immediate_callback cb,
+                                    void* data,
+                                    v8::Local<v8::Object> obj) {
+  CreateImmediate(cb, data, obj, false);
+}
+
 inline performance::performance_state* Environment::performance_state() {
   return performance_state_.get();
 }