diff --git a/cli/ops/dispatch_json.rs b/cli/ops/dispatch_json.rs
index b1a7bc723f..bfffd6d098 100644
--- a/cli/ops/dispatch_json.rs
+++ b/cli/ops/dispatch_json.rs
@@ -41,11 +41,19 @@ struct AsyncArgs {
   promise_id: Option<u64>,
 }
 
-pub fn json_op<D>(d: D) -> impl Fn(&[u8], Option<ZeroCopyBuf>) -> Op
+pub fn json_op<D>(
+  d: D,
+) -> impl Fn(&mut deno_core::Isolate, &[u8], Option<ZeroCopyBuf>) -> Op
 where
-  D: Fn(Value, Option<ZeroCopyBuf>) -> Result<JsonOp, OpError>,
+  D: Fn(
+    &mut deno_core::Isolate,
+    Value,
+    Option<ZeroCopyBuf>,
+  ) -> Result<JsonOp, OpError>,
 {
-  move |control: &[u8], zero_copy: Option<ZeroCopyBuf>| {
+  move |isolate: &mut deno_core::Isolate,
+        control: &[u8],
+        zero_copy: Option<ZeroCopyBuf>| {
     let async_args: AsyncArgs = match serde_json::from_slice(control) {
       Ok(args) => args,
       Err(e) => {
@@ -58,7 +66,7 @@ where
 
     let result = serde_json::from_slice(control)
       .map_err(OpError::from)
-      .and_then(|args| d(args, zero_copy));
+      .and_then(|args| d(isolate, args, zero_copy));
 
     // Convert to Op
     match result {
diff --git a/cli/ops/dispatch_minimal.rs b/cli/ops/dispatch_minimal.rs
index 7fdd12401e..37907d60c0 100644
--- a/cli/ops/dispatch_minimal.rs
+++ b/cli/ops/dispatch_minimal.rs
@@ -113,11 +113,15 @@ fn test_parse_min_record() {
   assert_eq!(parse_min_record(&buf), None);
 }
 
-pub fn minimal_op<D>(d: D) -> impl Fn(&[u8], Option<ZeroCopyBuf>) -> Op
+pub fn minimal_op<D>(
+  d: D,
+) -> impl Fn(&mut deno_core::Isolate, &[u8], Option<ZeroCopyBuf>) -> Op
 where
   D: Fn(bool, i32, Option<ZeroCopyBuf>) -> MinimalOp,
 {
-  move |control: &[u8], zero_copy: Option<ZeroCopyBuf>| {
+  move |_isolate: &mut deno_core::Isolate,
+        control: &[u8],
+        zero_copy: Option<ZeroCopyBuf>| {
     let mut record = match parse_min_record(control) {
       Some(r) => r,
       None => {
diff --git a/cli/ops/plugins.rs b/cli/ops/plugins.rs
index 816c7ebb49..c0dffc90f0 100644
--- a/cli/ops/plugins.rs
+++ b/cli/ops/plugins.rs
@@ -3,20 +3,21 @@ use crate::fs as deno_fs;
 use crate::op_error::OpError;
 use crate::ops::json_op;
 use crate::state::State;
-use deno_core::*;
+use deno_core::Isolate;
+use deno_core::OpDispatcher;
+use deno_core::OpId;
+use deno_core::PluginInitContext;
+use deno_core::PluginInitFn;
+use deno_core::ZeroCopyBuf;
 use dlopen::symbor::Library;
 use std::collections::HashMap;
 use std::ffi::OsStr;
 use std::path::Path;
-use std::rc::Rc;
 
-pub fn init(i: &mut Isolate, s: &State, r: Rc<deno_core::OpRegistry>) {
-  let r_ = r;
+pub fn init(i: &mut Isolate, s: &State) {
   i.register_op(
     "op_open_plugin",
-    s.core_op(json_op(s.stateful_op(move |state, args, zero_copy| {
-      op_open_plugin(&r_, state, args, zero_copy)
-    }))),
+    s.core_op(json_op(s.stateful_op2(op_open_plugin))),
   );
 }
 
@@ -52,7 +53,7 @@ struct OpenPluginArgs {
 }
 
 pub fn op_open_plugin(
-  registry: &Rc<deno_core::OpRegistry>,
+  isolate: &mut deno_core::Isolate,
   state: &State,
   args: Value,
   _zero_copy: Option<ZeroCopyBuf>,
@@ -91,8 +92,8 @@ pub fn op_open_plugin(
     // The inclusion of prefix and rid is designed to avoid any
     // op name collision beyond the bound of a single loaded
     // plugin instance.
-    let op_id = registry
-      .register(&format!("plugin_{}_{}", rid, op.0), state.core_op(op.1));
+    let op_id = isolate
+      .register_op(&format!("plugin_{}_{}", rid, op.0), state.core_op(op.1));
     plugin_resource.ops.insert(op.0, op_id);
   }
 
diff --git a/cli/ops/web_worker.rs b/cli/ops/web_worker.rs
index 8cade7d402..ee376719fd 100644
--- a/cli/ops/web_worker.rs
+++ b/cli/ops/web_worker.rs
@@ -12,7 +12,11 @@ use std::convert::From;
 pub fn web_worker_op<D>(
   sender: mpsc::Sender<WorkerEvent>,
   dispatcher: D,
-) -> impl Fn(Value, Option<ZeroCopyBuf>) -> Result<JsonOp, OpError>
+) -> impl Fn(
+  &mut deno_core::Isolate,
+  Value,
+  Option<ZeroCopyBuf>,
+) -> Result<JsonOp, OpError>
 where
   D: Fn(
     &mpsc::Sender<WorkerEvent>,
@@ -20,7 +24,8 @@ where
     Option<ZeroCopyBuf>,
   ) -> Result<JsonOp, OpError>,
 {
-  move |args: Value,
+  move |_isolate: &mut deno_core::Isolate,
+        args: Value,
         zero_copy: Option<ZeroCopyBuf>|
         -> Result<JsonOp, OpError> { dispatcher(&sender, args, zero_copy) }
 }
@@ -29,7 +34,11 @@ pub fn web_worker_op2<D>(
   handle: WebWorkerHandle,
   sender: mpsc::Sender<WorkerEvent>,
   dispatcher: D,
-) -> impl Fn(Value, Option<ZeroCopyBuf>) -> Result<JsonOp, OpError>
+) -> impl Fn(
+  &mut deno_core::Isolate,
+  Value,
+  Option<ZeroCopyBuf>,
+) -> Result<JsonOp, OpError>
 where
   D: Fn(
     WebWorkerHandle,
@@ -38,7 +47,8 @@ where
     Option<ZeroCopyBuf>,
   ) -> Result<JsonOp, OpError>,
 {
-  move |args: Value,
+  move |_isolate: &mut deno_core::Isolate,
+        args: Value,
         zero_copy: Option<ZeroCopyBuf>|
         -> Result<JsonOp, OpError> {
     dispatcher(handle.clone(), &sender, args, zero_copy)
diff --git a/cli/state.rs b/cli/state.rs
index 82ac8c4c16..8561901346 100644
--- a/cli/state.rs
+++ b/cli/state.rs
@@ -73,7 +73,7 @@ impl State {
   pub fn stateful_json_op<D>(
     &self,
     dispatcher: D,
-  ) -> impl Fn(&[u8], Option<ZeroCopyBuf>) -> Op
+  ) -> impl Fn(&mut deno_core::Isolate, &[u8], Option<ZeroCopyBuf>) -> Op
   where
     D: Fn(&State, Value, Option<ZeroCopyBuf>) -> Result<JsonOp, OpError>,
   {
@@ -85,18 +85,21 @@ impl State {
   pub fn core_op<D>(
     &self,
     dispatcher: D,
-  ) -> impl Fn(&[u8], Option<ZeroCopyBuf>) -> Op
+  ) -> impl Fn(&mut deno_core::Isolate, &[u8], Option<ZeroCopyBuf>) -> Op
   where
-    D: Fn(&[u8], Option<ZeroCopyBuf>) -> Op,
+    D: Fn(&mut deno_core::Isolate, &[u8], Option<ZeroCopyBuf>) -> Op,
   {
     let state = self.clone();
 
-    move |control: &[u8], zero_copy: Option<ZeroCopyBuf>| -> Op {
+    move |isolate: &mut deno_core::Isolate,
+          control: &[u8],
+          zero_copy: Option<ZeroCopyBuf>|
+          -> Op {
       let bytes_sent_control = control.len() as u64;
       let bytes_sent_zero_copy =
         zero_copy.as_ref().map(|b| b.len()).unwrap_or(0) as u64;
 
-      let op = dispatcher(control, zero_copy);
+      let op = dispatcher(isolate, control, zero_copy);
 
       match op {
         Op::Sync(buf) => {
@@ -162,15 +165,45 @@ impl State {
   pub fn stateful_op<D>(
     &self,
     dispatcher: D,
-  ) -> impl Fn(Value, Option<ZeroCopyBuf>) -> Result<JsonOp, OpError>
+  ) -> impl Fn(
+    &mut deno_core::Isolate,
+    Value,
+    Option<ZeroCopyBuf>,
+  ) -> Result<JsonOp, OpError>
   where
     D: Fn(&State, Value, Option<ZeroCopyBuf>) -> Result<JsonOp, OpError>,
   {
     let state = self.clone();
-    move |args: Value,
+    move |_isolate: &mut deno_core::Isolate,
+          args: Value,
           zero_copy: Option<ZeroCopyBuf>|
           -> Result<JsonOp, OpError> { dispatcher(&state, args, zero_copy) }
   }
+
+  pub fn stateful_op2<D>(
+    &self,
+    dispatcher: D,
+  ) -> impl Fn(
+    &mut deno_core::Isolate,
+    Value,
+    Option<ZeroCopyBuf>,
+  ) -> Result<JsonOp, OpError>
+  where
+    D: Fn(
+      &mut deno_core::Isolate,
+      &State,
+      Value,
+      Option<ZeroCopyBuf>,
+    ) -> Result<JsonOp, OpError>,
+  {
+    let state = self.clone();
+    move |isolate: &mut deno_core::Isolate,
+          args: Value,
+          zero_copy: Option<ZeroCopyBuf>|
+          -> Result<JsonOp, OpError> {
+      dispatcher(isolate, &state, args, zero_copy)
+    }
+  }
 }
 
 impl ModuleLoader for State {
diff --git a/cli/web_worker.rs b/cli/web_worker.rs
index 24318fc59e..fc1575c5f3 100644
--- a/cli/web_worker.rs
+++ b/cli/web_worker.rs
@@ -133,11 +133,10 @@ impl WebWorker {
       ops::fetch::init(isolate, &state);
 
       if has_deno_namespace {
-        let op_registry = isolate.op_registry.clone();
         ops::runtime_compiler::init(isolate, &state);
         ops::fs::init(isolate, &state);
         ops::fs_events::init(isolate, &state);
-        ops::plugins::init(isolate, &state, op_registry);
+        ops::plugins::init(isolate, &state);
         ops::net::init(isolate, &state);
         ops::tls::init(isolate, &state);
         ops::os::init(isolate, &state);
diff --git a/cli/worker.rs b/cli/worker.rs
index 6f2818980e..cdbf8c42db 100644
--- a/cli/worker.rs
+++ b/cli/worker.rs
@@ -222,7 +222,6 @@ impl MainWorker {
     let state_ = state.clone();
     let mut worker = Worker::new(name, startup_data, state_);
     {
-      let op_registry = worker.isolate.op_registry.clone();
       let isolate = &mut worker.isolate;
       ops::runtime::init(isolate, &state);
       ops::runtime_compiler::init(isolate, &state);
@@ -231,7 +230,7 @@ impl MainWorker {
       ops::fs::init(isolate, &state);
       ops::fs_events::init(isolate, &state);
       ops::io::init(isolate, &state);
-      ops::plugins::init(isolate, &state, op_registry);
+      ops::plugins::init(isolate, &state);
       ops::net::init(isolate, &state);
       ops::tls::init(isolate, &state);
       ops::os::init(isolate, &state);
diff --git a/core/es_isolate.rs b/core/es_isolate.rs
index 8c2e5b26de..f50a3abb01 100644
--- a/core/es_isolate.rs
+++ b/core/es_isolate.rs
@@ -580,14 +580,16 @@ pub mod tests {
 
     let mut isolate = EsIsolate::new(loader, StartupData::None, false);
 
-    let dispatcher =
-      move |control: &[u8], _zero_copy: Option<ZeroCopyBuf>| -> Op {
-        dispatch_count_.fetch_add(1, Ordering::Relaxed);
-        assert_eq!(control.len(), 1);
-        assert_eq!(control[0], 42);
-        let buf = vec![43u8, 0, 0, 0].into_boxed_slice();
-        Op::Async(futures::future::ready(buf).boxed())
-      };
+    let dispatcher = move |_isolate: &mut Isolate,
+                           control: &[u8],
+                           _zero_copy: Option<ZeroCopyBuf>|
+          -> Op {
+      dispatch_count_.fetch_add(1, Ordering::Relaxed);
+      assert_eq!(control.len(), 1);
+      assert_eq!(control[0], 42);
+      let buf = vec![43u8, 0, 0, 0].into_boxed_slice();
+      Op::Async(futures::future::ready(buf).boxed())
+    };
 
     isolate.register_op("test", dispatcher);
 
diff --git a/core/examples/http_bench.rs b/core/examples/http_bench.rs
index 27fefc8bbc..9e58080438 100644
--- a/core/examples/http_bench.rs
+++ b/core/examples/http_bench.rs
@@ -111,20 +111,22 @@ impl Isolate {
     F: 'static + Fn(State, u32, Option<ZeroCopyBuf>) -> Result<u32, Error>,
   {
     let state = self.state.clone();
-    let core_handler =
-      move |control_buf: &[u8], zero_copy_buf: Option<ZeroCopyBuf>| -> Op {
-        let state = state.clone();
-        let record = Record::from(control_buf);
-        let is_sync = record.promise_id == 0;
-        assert!(is_sync);
+    let core_handler = move |_isolate: &mut deno_core::Isolate,
+                             control_buf: &[u8],
+                             zero_copy_buf: Option<ZeroCopyBuf>|
+          -> Op {
+      let state = state.clone();
+      let record = Record::from(control_buf);
+      let is_sync = record.promise_id == 0;
+      assert!(is_sync);
 
-        let result: i32 = match handler(state, record.rid, zero_copy_buf) {
-          Ok(r) => r as i32,
-          Err(_) => -1,
-        };
-        let buf = RecordBuf::from(Record { result, ..record })[..].into();
-        Op::Sync(buf)
+      let result: i32 = match handler(state, record.rid, zero_copy_buf) {
+        Ok(r) => r as i32,
+        Err(_) => -1,
       };
+      let buf = RecordBuf::from(Record { result, ..record })[..].into();
+      Op::Sync(buf)
+    };
 
     self.core_isolate.register_op(name, core_handler);
   }
@@ -139,25 +141,27 @@ impl Isolate {
     <F::Ok as TryInto<i32>>::Error: Debug,
   {
     let state = self.state.clone();
-    let core_handler =
-      move |control_buf: &[u8], zero_copy_buf: Option<ZeroCopyBuf>| -> Op {
-        let state = state.clone();
-        let record = Record::from(control_buf);
-        let is_sync = record.promise_id == 0;
-        assert!(!is_sync);
+    let core_handler = move |_isolate: &mut deno_core::Isolate,
+                             control_buf: &[u8],
+                             zero_copy_buf: Option<ZeroCopyBuf>|
+          -> Op {
+      let state = state.clone();
+      let record = Record::from(control_buf);
+      let is_sync = record.promise_id == 0;
+      assert!(!is_sync);
 
-        let fut = async move {
-          let op = handler(state, record.rid, zero_copy_buf);
-          let result = op
-            .map_ok(|r| r.try_into().expect("op result does not fit in i32"))
-            .unwrap_or_else(|_| -1)
-            .await;
-          RecordBuf::from(Record { result, ..record })[..].into()
-        };
-
-        Op::Async(fut.boxed_local())
+      let fut = async move {
+        let op = handler(state, record.rid, zero_copy_buf);
+        let result = op
+          .map_ok(|r| r.try_into().expect("op result does not fit in i32"))
+          .unwrap_or_else(|_| -1)
+          .await;
+        RecordBuf::from(Record { result, ..record })[..].into()
       };
 
+      Op::Async(fut.boxed_local())
+    };
+
     self.core_isolate.register_op(name, core_handler);
   }
 }
diff --git a/core/isolate.rs b/core/isolate.rs
index 18cd84eae2..c289f38e84 100644
--- a/core/isolate.rs
+++ b/core/isolate.rs
@@ -28,7 +28,6 @@ use std::mem::forget;
 use std::ops::{Deref, DerefMut};
 use std::option::Option;
 use std::pin::Pin;
-use std::rc::Rc;
 use std::sync::{Arc, Mutex, Once};
 use std::task::Context;
 use std::task::Poll;
@@ -177,7 +176,7 @@ pub struct Isolate {
   pending_unref_ops: FuturesUnordered<PendingOpFuture>,
   have_unpolled_ops: bool,
   startup_script: Option<OwnedScript>,
-  pub op_registry: Rc<OpRegistry>,
+  pub op_registry: OpRegistry,
   waker: AtomicWaker,
   error_handler: Option<Box<IsolateErrorHandleFn>>,
 }
@@ -313,7 +312,7 @@ impl Isolate {
       pending_unref_ops: FuturesUnordered::new(),
       have_unpolled_ops: false,
       startup_script,
-      op_registry: Rc::new(OpRegistry::new()),
+      op_registry: OpRegistry::new(),
       waker: AtomicWaker::new(),
       error_handler: None,
     };
@@ -343,9 +342,9 @@ impl Isolate {
   /// corresponds to the second argument of Deno.core.dispatch().
   ///
   /// Requires runtime to explicitly ask for op ids before using any of the ops.
-  pub fn register_op<F>(&self, name: &str, op: F) -> OpId
+  pub fn register_op<F>(&mut self, name: &str, op: F) -> OpId
   where
-    F: Fn(&[u8], Option<ZeroCopyBuf>) -> Op + 'static,
+    F: Fn(&mut Isolate, &[u8], Option<ZeroCopyBuf>) -> Op + 'static,
   {
     self.op_registry.register(name, op)
   }
@@ -381,17 +380,14 @@ impl Isolate {
     control_buf: &[u8],
     zero_copy_buf: Option<ZeroCopyBuf>,
   ) -> Option<(OpId, Box<[u8]>)> {
-    let maybe_op = self.op_registry.call(op_id, control_buf, zero_copy_buf);
-
-    let op = match maybe_op {
-      Some(op) => op,
-      None => {
-        let message =
-          v8::String::new(scope, &format!("Unknown op id: {}", op_id)).unwrap();
-        let exception = v8::Exception::type_error(scope, message);
-        scope.isolate().throw_exception(exception);
-        return None;
-      }
+    let op = if let Some(dispatcher) = self.op_registry.get(op_id) {
+      dispatcher(self, control_buf, zero_copy_buf)
+    } else {
+      let message =
+        v8::String::new(scope, &format!("Unknown op id: {}", op_id)).unwrap();
+      let exception = v8::Exception::type_error(scope, message);
+      scope.isolate().throw_exception(exception);
+      return None;
     };
 
     debug_assert_eq!(self.shared.size(), 0);
@@ -768,56 +764,58 @@ pub mod tests {
 
     let mut isolate = Isolate::new(StartupData::None, false);
 
-    let dispatcher =
-      move |control: &[u8], _zero_copy: Option<ZeroCopyBuf>| -> Op {
-        dispatch_count_.fetch_add(1, Ordering::Relaxed);
-        match mode {
-          Mode::Async => {
-            assert_eq!(control.len(), 1);
-            assert_eq!(control[0], 42);
-            let buf = vec![43u8].into_boxed_slice();
-            Op::Async(futures::future::ready(buf).boxed())
-          }
-          Mode::AsyncUnref => {
-            assert_eq!(control.len(), 1);
-            assert_eq!(control[0], 42);
-            let fut = async {
-              // This future never finish.
-              futures::future::pending::<()>().await;
-              vec![43u8].into_boxed_slice()
-            };
-            Op::AsyncUnref(fut.boxed())
-          }
-          Mode::OverflowReqSync => {
-            assert_eq!(control.len(), 100 * 1024 * 1024);
-            let buf = vec![43u8].into_boxed_slice();
-            Op::Sync(buf)
-          }
-          Mode::OverflowResSync => {
-            assert_eq!(control.len(), 1);
-            assert_eq!(control[0], 42);
-            let mut vec = Vec::<u8>::new();
-            vec.resize(100 * 1024 * 1024, 0);
-            vec[0] = 99;
-            let buf = vec.into_boxed_slice();
-            Op::Sync(buf)
-          }
-          Mode::OverflowReqAsync => {
-            assert_eq!(control.len(), 100 * 1024 * 1024);
-            let buf = vec![43u8].into_boxed_slice();
-            Op::Async(futures::future::ready(buf).boxed())
-          }
-          Mode::OverflowResAsync => {
-            assert_eq!(control.len(), 1);
-            assert_eq!(control[0], 42);
-            let mut vec = Vec::<u8>::new();
-            vec.resize(100 * 1024 * 1024, 0);
-            vec[0] = 4;
-            let buf = vec.into_boxed_slice();
-            Op::Async(futures::future::ready(buf).boxed())
-          }
+    let dispatcher = move |_isolate: &mut Isolate,
+                           control: &[u8],
+                           _zero_copy: Option<ZeroCopyBuf>|
+          -> Op {
+      dispatch_count_.fetch_add(1, Ordering::Relaxed);
+      match mode {
+        Mode::Async => {
+          assert_eq!(control.len(), 1);
+          assert_eq!(control[0], 42);
+          let buf = vec![43u8].into_boxed_slice();
+          Op::Async(futures::future::ready(buf).boxed())
         }
-      };
+        Mode::AsyncUnref => {
+          assert_eq!(control.len(), 1);
+          assert_eq!(control[0], 42);
+          let fut = async {
+            // This future never finish.
+            futures::future::pending::<()>().await;
+            vec![43u8].into_boxed_slice()
+          };
+          Op::AsyncUnref(fut.boxed())
+        }
+        Mode::OverflowReqSync => {
+          assert_eq!(control.len(), 100 * 1024 * 1024);
+          let buf = vec![43u8].into_boxed_slice();
+          Op::Sync(buf)
+        }
+        Mode::OverflowResSync => {
+          assert_eq!(control.len(), 1);
+          assert_eq!(control[0], 42);
+          let mut vec = Vec::<u8>::new();
+          vec.resize(100 * 1024 * 1024, 0);
+          vec[0] = 99;
+          let buf = vec.into_boxed_slice();
+          Op::Sync(buf)
+        }
+        Mode::OverflowReqAsync => {
+          assert_eq!(control.len(), 100 * 1024 * 1024);
+          let buf = vec![43u8].into_boxed_slice();
+          Op::Async(futures::future::ready(buf).boxed())
+        }
+        Mode::OverflowResAsync => {
+          assert_eq!(control.len(), 1);
+          assert_eq!(control[0], 42);
+          let mut vec = Vec::<u8>::new();
+          vec.resize(100 * 1024 * 1024, 0);
+          vec[0] = 4;
+          let buf = vec.into_boxed_slice();
+          Op::Async(futures::future::ready(buf).boxed())
+        }
+      }
+    };
 
     isolate.register_op("test", dispatcher);
 
diff --git a/core/ops.rs b/core/ops.rs
index ab183f4ded..ed9b27e469 100644
--- a/core/ops.rs
+++ b/core/ops.rs
@@ -1,10 +1,10 @@
 // Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
+use crate::Isolate;
 use crate::ZeroCopyBuf;
 use futures::Future;
 use std::collections::HashMap;
 use std::pin::Pin;
 use std::rc::Rc;
-use std::sync::RwLock;
 
 pub type OpId = u32;
 
@@ -21,72 +21,48 @@ pub enum Op {
 }
 
 /// Main type describing op
-pub type OpDispatcher = dyn Fn(&[u8], Option<ZeroCopyBuf>) -> Op + 'static;
+pub type OpDispatcher =
+  dyn Fn(&mut Isolate, &[u8], Option<ZeroCopyBuf>) -> Op + 'static;
 
 #[derive(Default)]
 pub struct OpRegistry {
-  dispatchers: RwLock<Vec<Rc<OpDispatcher>>>,
-  name_to_id: RwLock<HashMap<String, OpId>>,
+  dispatchers: Vec<Rc<OpDispatcher>>,
+  name_to_id: HashMap<String, OpId>,
 }
 
 impl OpRegistry {
   pub fn new() -> Self {
-    let registry = Self::default();
-    let op_id = registry.register("ops", |_, _| {
-      // ops is a special op which is handled in call.
-      unreachable!()
+    let mut registry = Self::default();
+    let op_id = registry.register("ops", |isolate, _, _| {
+      let buf = isolate.op_registry.json_map();
+      Op::Sync(buf)
     });
     assert_eq!(op_id, 0);
     registry
   }
 
-  pub fn register<F>(&self, name: &str, op: F) -> OpId
+  pub fn register<F>(&mut self, name: &str, op: F) -> OpId
   where
-    F: Fn(&[u8], Option<ZeroCopyBuf>) -> Op + 'static,
+    F: Fn(&mut Isolate, &[u8], Option<ZeroCopyBuf>) -> Op + 'static,
   {
-    let mut lock = self.dispatchers.write().unwrap();
-    let op_id = lock.len() as u32;
+    let op_id = self.dispatchers.len() as u32;
 
-    let mut name_lock = self.name_to_id.write().unwrap();
-    let existing = name_lock.insert(name.to_string(), op_id);
+    let existing = self.name_to_id.insert(name.to_string(), op_id);
     assert!(
       existing.is_none(),
       format!("Op already registered: {}", name)
     );
-    lock.push(Rc::new(op));
-    drop(name_lock);
-    drop(lock);
+    self.dispatchers.push(Rc::new(op));
     op_id
   }
 
   fn json_map(&self) -> Buf {
-    let lock = self.name_to_id.read().unwrap();
-    let op_map_json = serde_json::to_string(&*lock).unwrap();
+    let op_map_json = serde_json::to_string(&self.name_to_id).unwrap();
     op_map_json.as_bytes().to_owned().into_boxed_slice()
   }
 
-  /// This function returns None only if op with given id doesn't exist in registry.
-  pub fn call(
-    &self,
-    op_id: OpId,
-    control: &[u8],
-    zero_copy_buf: Option<ZeroCopyBuf>,
-  ) -> Option<Op> {
-    // Op with id 0 has special meaning - it's a special op that is always
-    // provided to retrieve op id map. The map consists of name to `OpId`
-    // mappings.
-    if op_id == 0 {
-      return Some(Op::Sync(self.json_map()));
-    }
-    let lock = self.dispatchers.read().unwrap();
-    if let Some(op) = lock.get(op_id as usize) {
-      let op_ = Rc::clone(&op);
-      // This should allow for changes to the dispatcher list during a call.
-      drop(lock);
-      Some(op_(control, zero_copy_buf))
-    } else {
-      None
-    }
+  pub fn get(&self, op_id: OpId) -> Option<Rc<OpDispatcher>> {
+    self.dispatchers.get(op_id as usize).map(Rc::clone)
   }
 }
 
@@ -94,12 +70,12 @@ impl OpRegistry {
 fn test_op_registry() {
   use std::sync::atomic;
   use std::sync::Arc;
-  let op_registry = OpRegistry::new();
+  let mut op_registry = OpRegistry::new();
 
   let c = Arc::new(atomic::AtomicUsize::new(0));
   let c_ = c.clone();
 
-  let test_id = op_registry.register("test", move |_, _| {
+  let test_id = op_registry.register("test", move |_, _, _| {
     c_.fetch_add(1, atomic::Ordering::SeqCst);
     Op::Sync(Box::new([]))
   });
@@ -108,10 +84,12 @@ fn test_op_registry() {
   let mut expected = HashMap::new();
   expected.insert("ops".to_string(), 0);
   expected.insert("test".to_string(), 1);
-  let name_to_id = op_registry.name_to_id.read().unwrap();
-  assert_eq!(*name_to_id, expected);
+  assert_eq!(op_registry.name_to_id, expected);
 
-  let res = op_registry.call(test_id, &[], None).unwrap();
+  let mut isolate = Isolate::new(crate::StartupData::None, false);
+
+  let dispatch = op_registry.get(test_id).unwrap();
+  let res = dispatch(&mut isolate, &[], None);
   if let Op::Sync(buf) = res {
     assert_eq!(buf.len(), 0);
   } else {
@@ -119,40 +97,57 @@ fn test_op_registry() {
   }
   assert_eq!(c.load(atomic::Ordering::SeqCst), 1);
 
-  let res = op_registry.call(100, &[], None);
-  assert!(res.is_none());
+  assert!(op_registry.get(100).is_none());
 }
 
 #[test]
 fn register_op_during_call() {
   use std::sync::atomic;
   use std::sync::Arc;
-  let op_registry = Arc::new(OpRegistry::new());
+  use std::sync::Mutex;
+  let op_registry = Arc::new(Mutex::new(OpRegistry::new()));
 
   let c = Arc::new(atomic::AtomicUsize::new(0));
   let c_ = c.clone();
 
   let op_registry_ = op_registry.clone();
-  let test_id = op_registry.register("dynamic_register_op", move |_, _| {
-    let c__ = c_.clone();
-    op_registry_.register("test", move |_, _| {
-      c__.fetch_add(1, atomic::Ordering::SeqCst);
+
+  let test_id = {
+    let mut g = op_registry.lock().unwrap();
+    g.register("dynamic_register_op", move |_, _, _| {
+      let c__ = c_.clone();
+      let mut g = op_registry_.lock().unwrap();
+      g.register("test", move |_, _, _| {
+        c__.fetch_add(1, atomic::Ordering::SeqCst);
+        Op::Sync(Box::new([]))
+      });
       Op::Sync(Box::new([]))
-    });
-    Op::Sync(Box::new([]))
-  });
+    })
+  };
   assert!(test_id != 0);
 
-  op_registry.call(test_id, &[], None);
+  let mut isolate = Isolate::new(crate::StartupData::None, false);
+
+  let dispatcher1 = {
+    let g = op_registry.lock().unwrap();
+    g.get(test_id).unwrap()
+  };
+  dispatcher1(&mut isolate, &[], None);
 
   let mut expected = HashMap::new();
   expected.insert("ops".to_string(), 0);
   expected.insert("dynamic_register_op".to_string(), 1);
   expected.insert("test".to_string(), 2);
-  let name_to_id = op_registry.name_to_id.read().unwrap();
-  assert_eq!(*name_to_id, expected);
+  {
+    let g = op_registry.lock().unwrap();
+    assert_eq!(g.name_to_id, expected);
+  }
 
-  let res = op_registry.call(2, &[], None).unwrap();
+  let dispatcher2 = {
+    let g = op_registry.lock().unwrap();
+    g.get(2).unwrap()
+  };
+  let res = dispatcher2(&mut isolate, &[], None);
   if let Op::Sync(buf) = res {
     assert_eq!(buf.len(), 0);
   } else {
@@ -160,6 +155,6 @@ fn register_op_during_call() {
   }
   assert_eq!(c.load(atomic::Ordering::SeqCst), 1);
 
-  let res = op_registry.call(100, &[], None);
-  assert!(res.is_none());
+  let g = op_registry.lock().unwrap();
+  assert!(g.get(100).is_none());
 }
diff --git a/core/plugins.rs b/core/plugins.rs
index c6e63c9758..a423790bca 100644
--- a/core/plugins.rs
+++ b/core/plugins.rs
@@ -1,5 +1,7 @@
-use crate::isolate::ZeroCopyBuf;
-use crate::ops::Op;
+// TODO(ry) This plugin module is superfluous. Try to remove definitions for
+// "init_fn!", "PluginInitFn", and "PluginInitContext".
+
+use crate::ops::OpDispatcher;
 
 pub type PluginInitFn = fn(context: &mut dyn PluginInitContext);
 
@@ -7,7 +9,7 @@ pub trait PluginInitContext {
   fn register_op(
     &mut self,
     name: &str,
-    op: Box<dyn Fn(&[u8], Option<ZeroCopyBuf>) -> Op + 'static>,
+    op: Box<OpDispatcher>, // TODO(ry) rename to dispatcher, not op.
   );
 }
 
diff --git a/deno_typescript/lib.rs b/deno_typescript/lib.rs
index cd843041e2..24ecd62877 100644
--- a/deno_typescript/lib.rs
+++ b/deno_typescript/lib.rs
@@ -49,11 +49,14 @@ pub struct TSState {
 fn compiler_op<D>(
   ts_state: Arc<Mutex<TSState>>,
   dispatcher: D,
-) -> impl Fn(&[u8], Option<ZeroCopyBuf>) -> Op
+) -> impl Fn(&mut deno_core::Isolate, &[u8], Option<ZeroCopyBuf>) -> Op
 where
   D: Fn(&mut TSState, &[u8]) -> Op,
 {
-  move |control: &[u8], zero_copy_buf: Option<ZeroCopyBuf>| -> Op {
+  move |_isolate: &mut deno_core::Isolate,
+        control: &[u8],
+        zero_copy_buf: Option<ZeroCopyBuf>|
+        -> Op {
     assert!(zero_copy_buf.is_none()); // zero_copy_buf unused in compiler.
     let mut s = ts_state.lock().unwrap();
     dispatcher(&mut s, control)
@@ -326,11 +329,14 @@ pub fn trace_serializer() {
 /// Isolate.
 pub fn op_fetch_asset<S: ::std::hash::BuildHasher>(
   custom_assets: HashMap<String, PathBuf, S>,
-) -> impl Fn(&[u8], Option<ZeroCopyBuf>) -> Op {
+) -> impl Fn(&mut deno_core::Isolate, &[u8], Option<ZeroCopyBuf>) -> Op {
   for (_, path) in custom_assets.iter() {
     println!("cargo:rerun-if-changed={}", path.display());
   }
-  move |control: &[u8], zero_copy_buf: Option<ZeroCopyBuf>| -> Op {
+  move |_isolate: &mut deno_core::Isolate,
+        control: &[u8],
+        zero_copy_buf: Option<ZeroCopyBuf>|
+        -> Op {
     assert!(zero_copy_buf.is_none()); // zero_copy_buf unused in this op.
     let name = std::str::from_utf8(control).unwrap();
 
diff --git a/test_plugin/src/lib.rs b/test_plugin/src/lib.rs
index 70ba6d9b24..c88052e9a0 100644
--- a/test_plugin/src/lib.rs
+++ b/test_plugin/src/lib.rs
@@ -13,7 +13,11 @@ fn init(context: &mut dyn PluginInitContext) {
 }
 init_fn!(init);
 
-pub fn op_test_sync(data: &[u8], zero_copy: Option<ZeroCopyBuf>) -> Op {
+pub fn op_test_sync(
+  _isolate: &mut deno_core::Isolate,
+  data: &[u8],
+  zero_copy: Option<ZeroCopyBuf>,
+) -> Op {
   if let Some(buf) = zero_copy {
     let data_str = std::str::from_utf8(&data[..]).unwrap();
     let buf_str = std::str::from_utf8(&buf[..]).unwrap();
@@ -27,7 +31,11 @@ pub fn op_test_sync(data: &[u8], zero_copy: Option<ZeroCopyBuf>) -> Op {
   Op::Sync(result_box)
 }
 
-pub fn op_test_async(data: &[u8], zero_copy: Option<ZeroCopyBuf>) -> Op {
+pub fn op_test_async(
+  _isolate: &mut deno_core::Isolate,
+  data: &[u8],
+  zero_copy: Option<ZeroCopyBuf>,
+) -> Op {
   let data_str = std::str::from_utf8(&data[..]).unwrap().to_string();
   let fut = async move {
     if let Some(buf) = zero_copy {