diff --git a/docs/src/Docs/UV/Async.md b/docs/src/Docs/UV/Async.md
index 3ab6c5a..192217c 100644
--- a/docs/src/Docs/UV/Async.md
+++ b/docs/src/Docs/UV/Async.md
@@ -125,7 +125,7 @@ parameters {auto l : UVLoop}
   onConnection ac server = do
     putOutLn "Got a connection"
     client <- acceptTcp server
-    _      <- streamRead ac client $ \case
+    _      <- streamReadWrite ac client $ \case
       Done     => pure (Just ())
       Data val => bytesOut val >> write client val $> Nothing
       Err x    => throw x
@@ -139,6 +139,7 @@ parameters {auto l : UVLoop}
       Right srv => onConnection ac srv
 
     ignore $ onSignal SIGINT
+    putOutLn "Shutting down server..."
     cancel
 
 main : IO ()
diff --git a/src/IO/Async/Async.idr b/src/IO/Async/Async.idr
index 63279e9..fd39cd3 100644
--- a/src/IO/Async/Async.idr
+++ b/src/IO/Async/Async.idr
@@ -70,6 +70,9 @@ data Prim : List Type -> Type -> Type where
   -- spawn a new fiber with the given computation
   Start  : Async es a -> Prim es (Fiber es a)
 
+  -- out cancel state that can be used when spawning a new fiber.
+  Self   : Prim es (MVar CancelState)
+
   -- repeatedly poll the given `IO` action until int yields a `Just`
   Poll   : IO (Maybe $ Outcome es a) -> Prim es a
 
@@ -99,6 +102,7 @@ primType (CB f)    = "CB"
 primType (Start x) = "Start of \{type x}"
 primType (Poll x)  = "Poll"
 primType Cancel    = "Cancel"
+primType Self      = "Self"
 
 type (AP c x)   = "AP(\{disp c}) of \{primType x}"
 type (AB c x f) = "AB(\{disp c}) of \{type x}"
@@ -150,11 +154,22 @@ throw = fail . inject
 -- Cancelling fibers
 --------------------------------------------------------------------------------
 
-||| Sets the given computation's cancelability to "cancelable".
+||| Sets the given computation's cancelability to "cancelable" if it
+||| is currently at "parent".
+|||
+||| If you plan to enforce cancelability no matter what, use
+||| `strictCancelable`.
 export
 cancelable : Async es a -> Async es a
-cancelable (AP _ x)   = AP C x
-cancelable (AB _ x f) = AB C x f
+cancelable (AP P x)   = AP C x
+cancelable (AB P x f) = AB C x f
+cancelable x          = x
+
+||| Sets the given computation's cancelability to "cancelable".
+export
+strictCancelable : Async es a -> Async es a
+strictCancelable (AP _ x)   = AP C x
+strictCancelable (AB _ x f) = AB C x f
 
 ||| Sets the given computation's cancelability to "uncancelable".
 export
@@ -204,7 +219,7 @@ HasIO (Async es) where
 export
 catch : (HSum es -> Async fs a) -> Async es a -> Async fs a
 catch f as =
-  AB U as $ \case
+  AB U (cancelable as) $ \case
     Succeeded a => pure a
     Error err   => f err
     Canceled    => canceled
@@ -235,7 +250,7 @@ guarantee :
   -> (cleanup : Outcome es a -> Async [] ())
   -> Async es a
 guarantee as fun =
-  AB U as (\o => AB U (fun o) (\_ => sync $ pure o))
+  AB U (cancelable as) (\o => AB U (fun o) (\_ => sync $ pure o))
 
 ||| Guarantees to run the given cleanup hook in case a fiber
 ||| has been canceled.
@@ -375,6 +390,10 @@ export %inline
 raceEither : (x : Async es a) -> (y : Async es b) -> Async es (Either a b)
 raceEither x y = race (map Left x) (map Right y)
 
+export %inline
+self : Async es (MVar CancelState)
+self = AP P Self
+
 --------------------------------------------------------------------------------
 -- Evaluation
 --------------------------------------------------------------------------------
@@ -491,6 +510,8 @@ parameters {auto ctxt : AsyncContext}
           | MkIORes (Just v) w2 => MkIORes (Done b v) w2
      in MkIORes (Cede b . AP c $ Poll x) w2
 
+  prim m b c Self w = MkIORes (Done b $ Succeeded m) w
+
   prim m b c Cancel w = MkIORes (Done True Canceled) w
 
   step :
@@ -527,13 +548,22 @@ parameters {auto ctxt : AsyncContext}
 -- Running asynchronous computations
 --------------------------------------------------------------------------------
 
+export
+childOnAsync :
+     {auto ctxt : AsyncContext}
+  -> (parent : Maybe $ MVar CancelState)
+  -> Async es a
+  -> (Outcome es a -> IO ())
+  -> IO ()
+childOnAsync parent as cb = do
+  fb <- newFiber parent
+  eval (EST fb (guarantee as (liftIO . cb)) [])
+
 ||| Runs the given asynchronous computation to completion
 ||| invoking the given callback once it is done.
-export
+export %inline
 onAsync : AsyncContext => Async es a -> (Outcome es a -> IO ()) -> IO ()
-onAsync as cb = do
-  fb  <- newFiber Nothing
-  eval (EST fb (guarantee as (liftIO . cb)) [])
+onAsync = childOnAsync Nothing
 
 ||| Asynchronously runs the given computation to completion.
 export %inline
diff --git a/src/IO/Async/MVar.idr b/src/IO/Async/MVar.idr
index 7200806..13d150b 100644
--- a/src/IO/Async/MVar.idr
+++ b/src/IO/Async/MVar.idr
@@ -118,126 +118,3 @@ complete d v = do
          Nothing => (Just v, True)
   conditionBroadcast d.cond
   pure b
-
---------------------------------------------------------------------------------
--- MQueue
---------------------------------------------------------------------------------
-
-||| A thread-safe work queue.
-export
-record MQueue a where
-  [noHints]
-  constructor MQ
-  queue : MVar (Queue a)
-  cond  : Condition
-
-export
-newMQueue : IO (MQueue a)
-newMQueue = [| MQ (newMVar empty) makeCondition |]
-
-export
-enqueue : MQueue a -> a -> IO ()
-enqueue q v = modifyMVar q.queue (`enqueue` v) >> conditionSignal q.cond
-
-export
-enqueueAll : MQueue a -> List a -> IO ()
-enqueueAll q [] = pure ()
-enqueueAll q vs = modifyMVar q.queue (`enqueueAll` vs) >> conditionSignal q.cond
-
-covering
-dequeue' : Bool -> MQueue a -> IO a
-dequeue' b q = do
-  when b (mutexAcquire q.queue.lock)
-  q1 <- readIORef q.queue.ref
-  case dequeue q1 of
-    Nothing => do
-      conditionWait q.cond q.queue.lock
-      dequeue' False q
-    Just (v,q2) => do
-      writeIORef q.queue.ref q2
-      mutexRelease q.queue.lock
-      pure v
-
-export covering %inline
-dequeue : MQueue a -> IO a
-dequeue = dequeue' True
-
---------------------------------------------------------------------------------
--- Worker
---------------------------------------------------------------------------------
---
--- export
--- record WorkST a where
---   constructor W
---   stopped : IORef Bool
---   queue   : MQueue a
---   act     : (a -> IO ()) -> a -> IO ()
---
--- export
--- newWorkST : ((a -> IO ()) -> a -> IO ()) -> IO (WorkST a)
--- newWorkST fun = [| W (newIORef False) newMQueue (pure fun) |]
---
--- namespace WorkST
---   export
---   stop : WorkST a -> IO ()
---   stop w = do
---     mutexAcquire w.queue.queue.lock
---     writeIORef w.stopped True
---     conditionBroadcast w.queue.cond
---     mutexRelease w.queue.queue.lock
---
---   export %inline
---   submit : a -> WorkST a -> IO ()
---   submit v w = enqueue w.queue v
---
---   export %inline
---   submitAll : List a -> WorkST a -> IO ()
---   submitAll vs w = enqueueAll w.queue vs
---
---   covering
---   process' : Bool -> WorkST a -> IO ()
---   process' b w = do
---     when b (mutexAcquire w.queue.queue.lock)
---     q1    <- readIORef w.queue.queue.ref
---     case dequeue q1 of
---       Nothing => do
---         False <- readIORef w.stopped
---           | True => mutexRelease w.queue.queue.lock
---         conditionWait w.queue.cond w.queue.queue.lock
---         process' False w
---
---       Just (v,q2) => do
---         writeIORef w.queue.queue.ref q2
---         mutexRelease w.queue.queue.lock
---         w.act (`submit` w) v
---         process' True w
---
---   export covering %inline
---   process : WorkST a -> IO ()
---   process = process' True
---
--- export
--- record WorkPool a where
---   constructor WP
---   st : WorkST a
---   ts : List ThreadID
---
--- export covering
--- newWorkPool : (n : Nat) -> ((a -> IO ()) -> a -> IO ()) -> IO (WorkPool a)
--- newWorkPool n fun = do
---   w  <- newWorkST fun
---   ts <- traverse (\x => fork $ process w) [1..n]
---   pure $ WP w ts
---
--- namespace WorkPool
---   export
---   stop : WorkPool a -> IO ()
---   stop (WP st ts) = stop st >> traverse_ (\x => threadWait x >> putStrLn "Thread done") ts
---
---   export %inline
---   submit : a -> WorkPool a -> IO ()
---   submit v = submit v . st
---
---   export %inline
---   submitAll : List a -> WorkPool a -> IO ()
---   submitAll vs = submitAll vs . st
diff --git a/src/System/UV/File.idr b/src/System/UV/File.idr
index b07666b..8fe6b3c 100644
--- a/src/System/UV/File.idr
+++ b/src/System/UV/File.idr
@@ -171,7 +171,7 @@ parameters {auto l   : UVLoop}
   readBytes : File -> Bits32 -> Async es ByteString
   readBytes f size =
     use1 (mallocPtrs Bits8 size) $ \cs =>
-      cancelable $ uvAsync $ \cb => do
+      uvAsync $ \cb => do
         async (uv_fs_read l.loop f.file cs size (-1)) (readOutcome cs cb)
 
   export
@@ -189,7 +189,7 @@ parameters {auto l   : UVLoop}
     -> (ByteString -> Async es (Maybe b))
     -> Async es (Maybe b)
   streamFileUntil {b} path size fun =
-    use1 (fsOpen path RDONLY 0) $ \h => cancelable $ go h
+    use1 (fsOpen path RDONLY 0) $ \h => go h
     where
       go : File -> Async es (Maybe b)
       go h = do
diff --git a/src/System/UV/Loop.idr b/src/System/UV/Loop.idr
index 12d8555..4607653 100644
--- a/src/System/UV/Loop.idr
+++ b/src/System/UV/Loop.idr
@@ -80,7 +80,7 @@ parameters {auto has : Has UVError es}
     -> Async es a
   uvOnce p close reg =
     finally
-      (cancelable $ async $ \cb => do
+      (async $ \cb => do
          n <- reg (cb . Succeeded)
          case uvRes n of
            Left err => cb (Error err)
@@ -108,12 +108,14 @@ parameters {auto has : Has UVError es}
     -> Async es (Fiber es b)
   uvForever to p close reg =
     start $ finally
-      (cancelable $ forever $ \cb => do
-         n <- reg (\va => onAsync (to va) cb)
-         case uvRes n of
-           Left err => cb (Error err)
-           Right () => pure ()
-           )
+      (do
+        cc <- self
+        forever $ \cb => do
+          n <- reg (\va => childOnAsync (Just cc) (to va) cb)
+          case uvRes n of
+            Left err => cb (Error err)
+            Right () => pure ()
+      )
       (close p)
 
   export
diff --git a/src/System/UV/Stream.idr b/src/System/UV/Stream.idr
index 45c3700..eb4c690 100644
--- a/src/System/UV/Stream.idr
+++ b/src/System/UV/Stream.idr
@@ -34,6 +34,11 @@ export
 parameters {auto l : UVLoop}
            {auto has : Has UVError es}
 
+  close_stream : Ptr Stream -> Async [] ()
+  close_stream x = do
+    uv_read_stop x
+    ignore (uv_shutdown x $ \_,_ => uv_close x %search)
+
   export
   streamRead :
        AllocCB
@@ -45,6 +50,17 @@ parameters {auto l : UVLoop}
     uvForever run h (\x => uv_read_stop x) $ \cb =>
       uv_read_start h ac (\_,n,buf => toMsg n buf >>= cb)
 
+  export
+  streamReadWrite :
+       AllocCB
+    -> Ptr t
+    -> {auto 0 cstt : PCast t Stream}
+    -> (ReadRes ByteString -> Async es (Maybe a))
+    -> Async es (Fiber es a)
+  streamReadWrite ac h run = do
+    uvForever run h (close_stream . castPtr) $ \cb =>
+      uv_read_start h ac (\_,n,buf => toMsg n buf >>= cb)
+
   export
   write :
        Ptr t
@@ -58,10 +74,10 @@ parameters {auto l : UVLoop}
   export
   listen :
        Ptr t
-    -> {auto 0 cstt : PCast t Stream}
+    -> {auto 0 cst : PCast t Stream}
     -> (Either UVError (Ptr Stream) -> Async es (Maybe a))
     -> Async es (Fiber es a)
-  listen server run =
-    uvForever run server (\_ => pure ()) $ \cb =>
+  listen {cst} server run =
+    uvForever run server (release . castPtr @{cst}) $ \cb =>
       uv_listen server 128 $ \p,res =>
         cb $ if res < 0 then Left $ fromCode res else Right p