diff --git a/src/rt/runtime.rs b/src/rt/runtime.rs
index d4f3347..dc9f056 100644
--- a/src/rt/runtime.rs
+++ b/src/rt/runtime.rs
@@ -1,4 +1,5 @@
 use std::cell::Cell;
+use std::cell::RefCell;
 use std::io;
 use std::iter;
 use std::ptr;
@@ -13,7 +14,6 @@ use crossbeam_utils::{
     thread::scope,
 };
 use once_cell::sync::Lazy;
-use once_cell::unsync::OnceCell;
 
 use crate::rt::Reactor;
 use crate::sync::Spinlock;
@@ -22,7 +22,7 @@ use crate::utils::{abort_on_panic, random};
 
 thread_local! {
     /// A reference to the current machine, if the current thread runs tasks.
-    static MACHINE: OnceCell<Arc<Machine>> = OnceCell::new();
+    static MACHINE: RefCell<Option<Arc<Machine>>> = RefCell::new(None);
 
     /// This flag is set to true whenever `task::yield_now()` is invoked.
     static YIELD_NOW: Cell<bool> = Cell::new(false);
@@ -105,7 +105,7 @@ impl Runtime {
         MACHINE.with(|machine| {
             // If the current thread is a worker thread, schedule it onto the current machine.
             // Otherwise, push it into the global task queue.
-            match machine.get() {
+            match &*machine.borrow() {
                 None => {
                     self.injector.push(task);
                     self.notify();
@@ -130,12 +130,13 @@ impl Runtime {
 
                     // println!("getting idle thread");
                     let sched = self.sched.lock().unwrap();
-                    'inner: for thread in sched.threads.iter() {
+                    'inner: for (i, thread) in sched.threads.iter().enumerate() {
                         // grab the first parked thread
                         if thread
                             .parked
                             .compare_and_swap(true, false, Ordering::Acquire)
                         {
+                            println!("unpark thread {}", i);
                             // transfer the machine
                             thread
                                 .machine_sender
@@ -165,21 +166,31 @@ impl Runtime {
                             .spawn(move |_| {
                                 abort_on_panic(|| {
                                     loop {
+                                        println!("checking park loop {}", i);
                                         while parked2.load(Ordering::Acquire) {
                                             parker.park();
                                             // TODO: shutdown if idle for too long
                                         }
-                                        // println!("thread unparked {}", i);
+                                        println!("thread unparked {}", i);
                                         // when this thread is unparked, retrieve machine
                                         let m: Arc<Machine> =
                                             machine_recv.recv().expect("failed to receive machine");
+
                                         // store it in the thread local
-                                        let _ = MACHINE.with(|machine| machine.set(m.clone()));
+                                        MACHINE.with(|machine| {
+                                            *machine.borrow_mut() = Some(m.clone());
+                                        });
                                         // run it
                                         m.run(self);
+
                                         // when run ends, go into parked mode again
-                                        parked2.store(false, Ordering::Relaxed);
-                                        // println!("thread parked {}", i);
+                                        {
+                                            MACHINE.with(|machine| {
+                                                *machine.borrow_mut() = None;
+                                            });
+                                            parked2.store(true, Ordering::Relaxed);
+                                            println!("thread parked {}", i);
+                                        }
                                     }
                                 })
                             })
@@ -223,13 +234,14 @@ impl Runtime {
         // If no machine has been polling the reactor in a while, that means the runtime is
         // overloaded with work and we need to start another machine.
         if !sched.polling {
-            if !sched.progress {
-                if let Some(p) = sched.processors.pop() {
-                    let m = Arc::new(Machine::new(p));
-                    to_start.push(m.clone());
-                    sched.machines.push(m);
-                }
+            dbg!(sched.progress, sched.polling);
+            // if !sched.progress {
+            if let Some(p) = sched.processors.pop() {
+                let m = Arc::new(Machine::new(p));
+                to_start.push(m.clone());
+                sched.machines.push(m);
             }
+            // }
             sched.progress = false;
         }
 
@@ -429,11 +441,11 @@ impl Machine {
             runs = 0;
             fails = 0;
         }
-        // println!("thread break");
+        println!("thread break");
 
         // When shutting down the thread, take the processor out if still available.
         let opt_p = self.processor.lock().take();
-        // println!("processor {:?}", opt_p.is_some());
+        println!("processor {:?}", opt_p.is_some());
 
         // Return the processor to the scheduler and remove the machine.
         if let Some(p) = opt_p {
@@ -442,7 +454,7 @@ impl Machine {
             sched.processors.push(p);
             sched.machines.retain(|elem| !ptr::eq(&**elem, self));
         }
-        // println!("thread run stopped");
+        println!("thread run stopped");
     }
 }