worker: refactor thread id management

- Assign thread IDs to `Environment` instances, rather than Workers.
  This is more embedder-friendly than the current system, in which
  all “main threads” (if there are multiple ones) would get the
  id `0`.
- Because that means that `isMainThread === (threadId === 0)` no longer
  holds, refactor `isMainThread` into a separate entity. Implement it
  in a way that allows for future extensibility, because we use
  `isMainThread` in multiple different ways (determining whether there
  is a parent thread; determining whether the current thread has control
  of the current process; etc.).

PR-URL: https://github.com/nodejs/node/pull/25796
Reviewed-By: Joyee Cheung <joyeec9h3@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>
Reviewed-By: Denys Otrishko <shishugi@gmail.com>

1 files changed, 9 insertions, 3 deletions

diff --git a/src/env.h b/src/env.h
index 139694104e..25f1cd0689 100644
--- a/src/env.h
+++ b/src/env.h
@@ -595,6 +595,11 @@ class Environment {
     DISALLOW_COPY_AND_ASSIGN(TickInfo);
   };
 
+  enum Flags {
+    kNoFlags = 0,
+    kIsMainThread = 1
+  };
+
   static inline Environment* GetCurrent(v8::Isolate* isolate);
   static inline Environment* GetCurrent(v8::Local<v8::Context> context);
   static inline Environment* GetCurrent(
@@ -608,7 +613,8 @@ class Environment {
   static inline Environment* GetThreadLocalEnv();
 
   Environment(IsolateData* isolate_data,
-              v8::Local<v8::Context> context);
+              v8::Local<v8::Context> context,
+              Flags flags = Flags());
   ~Environment();
 
   void Start(bool start_profiler_idle_notifier);
@@ -761,7 +767,6 @@ class Environment {
 
   inline bool is_main_thread() const;
   inline uint64_t thread_id() const;
-  inline void set_thread_id(uint64_t id);
   inline worker::Worker* worker_context() const;
   inline void set_worker_context(worker::Worker* context);
   inline void add_sub_worker_context(worker::Worker* context);
@@ -1005,7 +1010,8 @@ class Environment {
 
   bool has_run_bootstrapping_code_ = false;
   bool can_call_into_js_ = true;
-  uint64_t thread_id_ = 0;
+  Flags flags_;
+  uint64_t thread_id_;
   std::unordered_set<worker::Worker*> sub_worker_contexts_;
 
   static void* const kNodeContextTagPtr;