2 files changed, 58 insertions, 0 deletions
diff --git a/ext/napi/lib.rs b/ext/napi/lib.rs
index faf8a5777..c9dc62a8b 100644
--- a/ext/napi/lib.rs
+++ b/ext/napi/lib.rs
@@ -9,11 +9,13 @@ use core::ptr::NonNull;
 use deno_core::error::type_error;
 use deno_core::error::AnyError;
 use deno_core::op2;
+use deno_core::parking_lot::RwLock;
 use deno_core::url::Url;
 use deno_core::ExternalOpsTracker;
 use deno_core::OpState;
 use deno_core::V8CrossThreadTaskSpawner;
 use std::cell::RefCell;
+use std::collections::HashMap;
 use std::path::Path;
 use std::path::PathBuf;
 use std::rc::Rc;
@@ -493,6 +495,15 @@ impl NapiPermissions for deno_permissions::PermissionsContainer {
   }
 }
 
+unsafe impl Sync for NapiModuleHandle {}
+unsafe impl Send for NapiModuleHandle {}
+#[derive(Clone, Copy)]
+struct NapiModuleHandle(*const NapiModule);
+
+static NAPI_LOADED_MODULES: std::sync::LazyLock<
+  RwLock<HashMap<String, NapiModuleHandle>>,
+> = std::sync::LazyLock::new(|| RwLock::new(HashMap::new()));
+
 #[op2(reentrant)]
 fn op_napi_open<NP, 'scope>(
   scope: &mut v8::HandleScope<'scope>,
@@ -575,11 +586,23 @@ where
   let exports = v8::Object::new(scope);
 
   let maybe_exports = if let Some(module_to_register) = maybe_module {
+    NAPI_LOADED_MODULES
+      .write()
+      .insert(path, NapiModuleHandle(module_to_register));
     // SAFETY: napi_register_module guarantees that `module_to_register` is valid.
     let nm = unsafe { &*module_to_register };
     assert_eq!(nm.nm_version, 1);
     // SAFETY: we are going blind, calling the register function on the other side.
     unsafe { (nm.nm_register_func)(env_ptr, exports.into()) }
+  } else if let Some(module_to_register) =
+    { NAPI_LOADED_MODULES.read().get(&path).copied() }
+  {
+    // SAFETY: this originated from `napi_register_module`, so the
+    // pointer should still be valid.
+    let nm = unsafe { &*module_to_register.0 };
+    assert_eq!(nm.nm_version, 1);
+    // SAFETY: we are going blind, calling the register function on the other side.
+    unsafe { (nm.nm_register_func)(env_ptr, exports.into()) }
   } else if let Ok(init) = unsafe {
     library.get::<napi_register_module_v1>(b"napi_register_module_v1")
   } {
diff --git a/tests/napi/init_test.js b/tests/napi/init_test.js
index 9db99d8a0..948682478 100644
--- a/tests/napi/init_test.js
+++ b/tests/napi/init_test.js
@@ -2,6 +2,7 @@
 
 import { Buffer } from "node:buffer";
 import { assert, libSuffix } from "./common.js";
+import { Worker } from "node:worker_threads";
 
 const ops = Deno[Deno.internal].core.ops;
 
@@ -13,3 +14,37 @@ Deno.test("ctr initialization (napi_module_register)", {
   assert(obj != null);
   assert(typeof obj === "object");
 });
+
+Deno.test("ctr initialization by multiple threads (napi_module_register)", {
+  ignore: Deno.build.os == "windows",
+}, async function () {
+  const path = new URL(`./module.${libSuffix}`, import.meta.url).pathname;
+  const obj = ops.op_napi_open(path, {}, Buffer, reportError);
+  const common = import.meta.resolve("./common.js");
+  assert(obj != null);
+  assert(typeof obj === "object");
+
+  const worker = new Worker(
+    `
+    import { Buffer } from "node:buffer";
+    import { parentPort } from "node:worker_threads";
+    import { assert } from "${common}";
+    
+    const ops = Deno[Deno.internal].core.ops;
+    const obj = ops.op_napi_open("${path}", {}, Buffer, reportError);
+    assert(obj != null);
+    assert(typeof obj === "object");
+    parentPort.postMessage("ok");
+    `,
+    {
+      eval: true,
+    },
+  );
+
+  const p = Promise.withResolvers();
+  worker.on("message", (_m) => {
+    p.resolve();
+  });
+
+  await p.promise;
+});