21 files changed, 196 insertions, 408 deletions

diff --git a/tokio/src/executor/blocking/mod.rs b/tokio/src/executor/blocking/mod.rs
index 92dc1c36..2947062b 100644
--- a/tokio/src/executor/blocking/mod.rs
+++ b/tokio/src/executor/blocking/mod.rs
@@ -249,6 +249,34 @@ impl Drop for PoolWaiter {
     }
 }
 
+/// Run the provided blocking function without blocking the executor.
+///
+/// In general, issuing a blocking call or performing a lot of compute in a
+/// future without yielding is not okay, as it may prevent the executor from
+/// driving other futures forward.  If you run a closure through this method,
+/// the current executor thread will relegate all its executor duties to another
+/// (possibly new) thread, and only then poll the task. Note that this requires
+/// additional synchronization.
+///
+/// # Examples
+///
+/// ```
+/// # async fn docs() {
+/// tokio::executor::blocking::in_place(move || {
+///     // do some compute-heavy work or call synchronous code
+/// });
+/// # }
+/// ```
+#[cfg(feature = "rt-full")]
+pub fn in_place<F, R>(f: F) -> R
+where
+    F: FnOnce() -> R,
+{
+    use crate::executor;
+
+    executor::enter::exit(|| executor::thread_pool::blocking(f))
+}
+
 /// Run the provided closure on a thread where blocking is acceptable.
 ///
 /// In general, issuing a blocking call or performing a lot of compute in a future without
diff --git a/tokio/src/executor/enter.rs b/tokio/src/executor/enter.rs
index 56b645a7..19ae26e0 100644
--- a/tokio/src/executor/enter.rs
+++ b/tokio/src/executor/enter.rs
@@ -1,6 +1,7 @@
 use std::cell::{Cell, RefCell};
 use std::error::Error;
 use std::fmt;
+#[cfg(feature = "rt-full")]
 use std::future::Future;
 use std::marker::PhantomData;
 
@@ -9,13 +10,13 @@ thread_local!(static ENTERED: Cell<bool> = Cell::new(false));
 /// Represents an executor context.
 ///
 /// For more details, see [`enter` documentation](fn.enter.html)
-pub struct Enter {
+pub(crate) struct Enter {
     _p: PhantomData<RefCell<()>>,
 }
 
 /// An error returned by `enter` if an execution scope has already been
 /// entered.
-pub struct EnterError {
+pub(crate) struct EnterError {
     _a: (),
 }
 
@@ -49,7 +50,7 @@ impl Error for EnterError {}
 /// # Error
 ///
 /// Returns an error if the current thread is already marked
-pub fn enter() -> Result<Enter, EnterError> {
+pub(crate) fn enter() -> Result<Enter, EnterError> {
     ENTERED.with(|c| {
         if c.get() {
             Err(EnterError { _a: () })
@@ -68,8 +69,8 @@ pub fn enter() -> Result<Enter, EnterError> {
 //
 // This is hidden for a reason. Do not use without fully understanding
 // executors. Misuing can easily cause your program to deadlock.
-#[doc(hidden)]
-pub fn exit<F: FnOnce() -> R, R>(f: F) -> R {
+#[cfg(feature = "rt-full")]
+pub(crate) fn exit<F: FnOnce() -> R, R>(f: F) -> R {
     // Reset in case the closure panics
     struct Reset;
     impl Drop for Reset {
@@ -100,7 +101,8 @@ pub fn exit<F: FnOnce() -> R, R>(f: F) -> R {
 impl Enter {
     /// Blocks the thread on the specified future, returning the value with
     /// which that future completes.
-    pub fn block_on<F: Future>(&mut self, mut f: F) -> F::Output {
+    #[cfg(feature = "rt-full")]
+    pub(crate) fn block_on<F: Future>(&mut self, mut f: F) -> F::Output {
         use crate::executor::park::{Park, ParkThread};
         use std::pin::Pin;
         use std::task::Context;
diff --git a/tokio/src/executor/loom/mod.rs b/tokio/src/executor/loom/mod.rs
index fa071d05..f6f9d23c 100644
--- a/tokio/src/executor/loom/mod.rs
+++ b/tokio/src/executor/loom/mod.rs
@@ -22,6 +22,7 @@ pub(crate) mod std {
 
 #[cfg(feature = "rt-full")]
 pub(crate) use self::std::rand;
+#[cfg(any(feature = "blocking", feature = "rt-current-thread"))]
 pub(crate) use self::std::sync;
 #[cfg(any(feature = "blocking", feature = "rt-full"))]
 pub(crate) use self::std::thread;
diff --git a/tokio/src/executor/loom/std/atomic_usize.rs b/tokio/src/executor/loom/std/atomic_usize.rs
index 3cabbded..4a424b1e 100644
--- a/tokio/src/executor/loom/std/atomic_usize.rs
+++ b/tokio/src/executor/loom/std/atomic_usize.rs
@@ -11,6 +11,7 @@ unsafe impl Send for AtomicUsize {}
 unsafe impl Sync for AtomicUsize {}
 
 impl AtomicUsize {
+    #[cfg(feature = "rt-current-thread")]
     pub(crate) fn new(val: usize) -> AtomicUsize {
         let inner = UnsafeCell::new(std::sync::atomic::AtomicUsize::new(val));
         AtomicUsize { inner }
diff --git a/tokio/src/executor/loom/std/mod.rs b/tokio/src/executor/loom/std/mod.rs
index eb865d98..3293f440 100644
--- a/tokio/src/executor/loom/std/mod.rs
+++ b/tokio/src/executor/loom/std/mod.rs
@@ -56,11 +56,13 @@ pub(crate) mod rand {
 }
 
 pub(crate) mod sync {
+    #[cfg(any(feature = "blocking", feature = "rt-current-thread"))]
     pub(crate) use std::sync::{Arc, Condvar, Mutex};
 
     pub(crate) mod atomic {
         #[cfg(feature = "rt-full")]
         pub(crate) use crate::executor::loom::std::atomic_u32::AtomicU32;
+        #[cfg(feature = "rt-current-thread")]
         pub(crate) use crate::executor::loom::std::atomic_usize::AtomicUsize;
 
         #[cfg(feature = "rt-full")]
diff --git a/tokio/src/executor/mod.rs b/tokio/src/executor/mod.rs
index a888c61b..fa2b29e4 100644
--- a/tokio/src/executor/mod.rs
+++ b/tokio/src/executor/mod.rs
@@ -44,8 +44,10 @@
 #[macro_use]
 mod tests;
 
+#[cfg(feature = "rt-current-thread")]
 mod enter;
-pub use self::enter::{enter, exit, Enter, EnterError};
+#[cfg(feature = "rt-current-thread")]
+pub(crate) use self::enter::enter;
 
 mod global;
 pub use self::global::spawn;
@@ -71,6 +73,4 @@ pub mod blocking;
 pub(crate) mod current_thread;
 
 #[cfg(feature = "rt-full")]
-pub mod thread_pool;
-
-pub use futures_util::future::RemoteHandle;
+pub(crate) mod thread_pool;
diff --git a/tokio/src/executor/park/mod.rs b/tokio/src/executor/park/mod.rs
index 16c78da8..9d6d508f 100644
--- a/tokio/src/executor/park/mod.rs
+++ b/tokio/src/executor/park/mod.rs
@@ -44,8 +44,10 @@
 //! [up]: trait.Unpark.html
 //! [mio]: https://docs.rs/mio/0.6/mio/struct.Poll.html
 
+#[cfg(feature = "rt-full")]
 mod thread;
-pub use self::thread::{ParkError, ParkThread, UnparkThread};
+#[cfg(feature = "rt-full")]
+pub(crate) use self::thread::ParkThread;
 
 use std::sync::Arc;
 use std::time::Duration;
diff --git a/tokio/src/executor/park/thread.rs b/tokio/src/executor/park/thread.rs
index af3d632b..c48b418d 100644
--- a/tokio/src/executor/park/thread.rs
+++ b/tokio/src/executor/park/thread.rs
@@ -3,10 +3,8 @@ use crate::executor::loom::sync::{Arc, Condvar, Mutex};
 use crate::executor::park::{Park, Unpark};
 
 use std::marker::PhantomData;
-use std::mem;
 use std::rc::Rc;
 use std::sync::atomic::Ordering;
-use std::task::{RawWaker, RawWakerVTable, Waker};
 use std::time::Duration;
 
 /// Blocks the current thread using a condition variable.
@@ -20,7 +18,7 @@ use std::time::Duration;
 /// means that an instance of `ParkThread` might be unblocked by a handle
 /// associated with a different `ParkThread` instance.
 #[derive(Debug)]
-pub struct ParkThread {
+pub(crate) struct ParkThread {
     _anchor: PhantomData<Rc<()>>,
 }
 
@@ -30,7 +28,7 @@ pub struct ParkThread {
 ///
 /// [`ParkThread`]: struct.ParkThread.html
 #[derive(Debug)]
-pub struct ParkError {
+pub(crate) struct ParkError {
     _p: (),
 }
 
@@ -40,7 +38,7 @@ struct Parker {
 
 /// Unblocks a thread that was blocked by `ParkThread`.
 #[derive(Clone, Debug)]
-pub struct UnparkThread {
+pub(crate) struct UnparkThread {
     inner: Arc<Inner>,
 }
 
@@ -62,7 +60,7 @@ thread_local! {
 // ==== impl Parker ====
 
 impl Parker {
-    pub(crate) fn new() -> Self {
+    fn new() -> Self {
         Self {
             unparker: Arc::new(Inner {
                 state: AtomicUsize::new(IDLE),
@@ -72,15 +70,15 @@ impl Parker {
         }
     }
 
-    pub(crate) fn unparker(&self) -> &Arc<Inner> {
+    fn unparker(&self) -> &Arc<Inner> {
         &self.unparker
     }
 
-    pub(crate) fn park(&self) -> Result<(), ParkError> {
+    fn park(&self) -> Result<(), ParkError> {
         self.unparker.park(None)
     }
 
-    pub(crate) fn park_timeout(&self, timeout: Duration) -> Result<(), ParkError> {
+    fn park_timeout(&self, timeout: Duration) -> Result<(), ParkError> {
         self.unparker.park(Some(timeout))
     }
 }
@@ -88,17 +86,8 @@ impl Parker {
 // ==== impl Inner ====
 
 impl Inner {
-    #[allow(clippy::wrong_self_convention)]
-    pub(crate) fn into_raw(this: Arc<Inner>) -> *const () {
-        Arc::into_raw(this) as *const ()
-    }
-
-    pub(crate) unsafe fn from_raw(ptr: *const ()) -> Arc<Inner> {
-        Arc::from_raw(ptr as *const Inner)
-    }
-
     /// Park the current thread for at most `dur`.
-    pub(crate) fn park(&self, timeout: Option<Duration>) -> Result<(), ParkError> {
+    fn park(&self, timeout: Option<Duration>) -> Result<(), ParkError> {
         // If currently notified, then we skip sleeping. This is checked outside
         // of the lock to avoid acquiring a mutex if not necessary.
         match self.state.compare_and_swap(NOTIFY, IDLE, Ordering::SeqCst) {
@@ -140,7 +129,7 @@ impl Inner {
         Ok(())
     }
 
-    pub(crate) fn unpark(&self) {
+    fn unpark(&self) {
         // First, try transitioning from IDLE -> NOTIFY, this does not require a
         // lock.
         match self.state.compare_and_swap(IDLE, NOTIFY, Ordering::SeqCst) {
@@ -172,7 +161,7 @@ impl ParkThread {
     ///
     /// This type cannot be moved to other threads, so it should be created on
     /// the thread that the caller intends to park.
-    pub fn new() -> ParkThread {
+    pub(crate) fn new() -> ParkThread {
         ParkThread {
             _anchor: PhantomData,
         }
@@ -221,43 +210,64 @@ impl Unpark for UnparkThread {
     }
 }
 
-static VTABLE: RawWakerVTable = RawWakerVTable::new(clone, wake, wake_by_ref, drop_waker);
+#[cfg(feature = "rt-full")]
+mod waker {
+    use super::{Inner, UnparkThread};
+    use crate::executor::loom::sync::Arc;
+
+    use std::mem;
+    use std::task::{RawWaker, RawWakerVTable, Waker};
 
-impl UnparkThread {
-    pub(crate) fn into_waker(self) -> Waker {
-        unsafe {
-            let raw = unparker_to_raw_waker(self.inner);
-            Waker::from_raw(raw)
+    impl UnparkThread {
+        pub(crate) fn into_waker(self) -> Waker {
+            unsafe {
+                let raw = unparker_to_raw_waker(self.inner);
+                Waker::from_raw(raw)
+            }
         }
     }
-}
 
-unsafe fn unparker_to_raw_waker(unparker: Arc<Inner>) -> RawWaker {
-    RawWaker::new(Inner::into_raw(unparker), &VTABLE)
-}
+    impl Inner {
+        #[allow(clippy::wrong_self_convention)]
+        fn into_raw(this: Arc<Inner>) -> *const () {
+            Arc::into_raw(this) as *const ()
+        }
+
+        unsafe fn from_raw(ptr: *const ()) -> Arc<Inner> {
+            Arc::from_raw(ptr as *const Inner)
+        }
+    }
 
-unsafe fn clone(raw: *const ()) -> RawWaker {
-    let unparker = Inner::from_raw(raw);
+    unsafe fn unparker_to_raw_waker(unparker: Arc<Inner>) -> RawWaker {
+        RawWaker::new(
+            Inner::into_raw(unparker),
+            &RawWakerVTable::new(clone, wake, wake_by_ref, drop_waker),
+        )
+    }
 
-    // Increment the ref count
-    mem::forget(unparker.clone());
+    unsafe fn clone(raw: *const ()) -> RawWaker {
+        let unparker = Inner::from_raw(raw);
 
-    unparker_to_raw_waker(unparker)
-}
+        // Increment the ref count
+        mem::forget(unparker.clone());
 
-unsafe fn drop_waker(raw: *const ()) {
-    let _ = Inner::from_raw(raw);
-}
+        unparker_to_raw_waker(unparker)
+    }
 
-unsafe fn wake(raw: *const ()) {
-    let unparker = Inner::from_raw(raw);
-    unparker.unpark();
-}
+    unsafe fn drop_waker(raw: *const ()) {
+        let _ = Inner::from_raw(raw);
+    }
 
-unsafe fn wake_by_ref(raw: *const ()) {
-    let unparker = Inner::from_raw(raw);
-    unparker.unpark();
+    unsafe fn wake(raw: *const ()) {
+        let unparker = Inner::from_raw(raw);
+        unparker.unpark();
+    }
 
-    // We don't actually own a reference to the unparker
-    mem::forget(unparker);
+    unsafe fn wake_by_ref(raw: *const ()) {
+        let unparker = Inner::from_raw(raw);
+        unparker.unpark();
+
+        // We don't actually own a reference to the unparker
+        mem::forget(unparker);
+    }
 }
diff --git a/tokio/src/executor/thread_pool/builder.rs b/tokio/src/executor/thread_pool/builder.rs
index c1298a5a..f9d40350 100644
--- a/tokio/src/executor/thread_pool/builder.rs
+++ b/tokio/src/executor/thread_pool/builder.rs
@@ -2,13 +2,12 @@ use crate::executor::loom::sync::Arc;
 use crate::executor::loom::sys::num_cpus;
 use crate::executor::loom::thread;
 use crate::executor::park::Park;
-use crate::executor::thread_pool::park::DefaultPark;
 use crate::executor::thread_pool::{shutdown, worker, worker::Worker, Spawner, ThreadPool};
 
 use std::{fmt, usize};
 
 /// Builds a thread pool with custom configuration values.
-pub struct Builder {
+pub(crate) struct Builder {
     /// Number of worker threads to spawn
     pool_size: usize,
 
@@ -29,7 +28,7 @@ type Callback = Arc<Box<dyn Fn(usize, &mut dyn FnMut()) + Send + Sync>>;
 impl Builder {
     /// Returns a new thread pool builder initialized with default configuration
     /// values.
-    pub fn new() -> Builder {
+    pub(crate) fn new() -> Builder {
         Builder {
             pool_size: num_cpus(),
             name: "tokio-runtime-worker".to_string(),
@@ -44,17 +43,7 @@ impl Builder {
     /// this value on the smaller side.
     ///
     /// The default value is the number of cores available to the system.
-    ///
-    /// # Examples
-    ///
-    /// ```
-    /// use tokio::executor::thread_pool::Builder;
-    ///
-    /// let thread_pool = Builder::new()
-    ///     .num_threads(4)
-    ///     .build();
-    /// ```
-    pub fn num_threads(&mut self, value: usize) -> &mut Self {
+    pub(crate) fn num_threads(&mut self, value: usize) -> &mut Self {
         self.pool_size = value;
         self
     }
@@ -63,17 +52,7 @@ impl Builder {
     ///
     /// If this configuration is not set, then the thread will use the system
     /// default naming scheme.
-    ///
-    /// # Examples
-    ///
-    /// ```
-    /// use tokio::executor::thread_pool::Builder;
-    ///
-    /// let thread_pool = Builder::new()
-    ///     .name("my-pool")
-    ///     .build();
-    /// ```
-    pub fn name<S: Into<String>>(&mut self, val: S) -> &mut Self {
+    pub(crate) fn name<S: Into<String>>(&mut self, val: S) -> &mut Self {
         self.name = val.into();
         self
     }
@@ -85,17 +64,7 @@ impl Builder {
     ///
     /// The default stack size for spawned threads is 2 MiB, though this
     /// particular stack size is subject to change in the future.
-    ///
-    /// # Examples
-    ///
-    /// ```
-    /// use tokio::executor::thread_pool::Builder;
-    ///
-    /// let thread_pool = Builder::new()
-    ///     .stack_size(32 * 1024)
-    ///     .build();
-    /// ```
-    pub fn stack_size(&mut self, val: usize) -> &mut Self {
+    pub(crate) fn stack_size(&mut self, val: usize) -> &mut Self {
         self.stack_size = Some(val);
         self
     }
@@ -105,21 +74,7 @@ impl Builder {
     /// This function is provided a function that executes the worker and is
     /// expected to call it, otherwise the worker thread will shutdown without
     /// doing any work.
-    ///
-    /// # Examples
-    ///
-    /// ```
-    /// use tokio::executor::thread_pool::Builder;
-    ///
-    /// let thread_pool = Builder::new()
-    ///     .around_worker(|index, work| {
-    ///         println!("worker {} is starting up", index);
-    ///         work();
-    ///         println!("worker {} is shutting down", index);
-    ///     })
-    ///     .build();
-    /// ```
-    pub fn around_worker<F>(&mut self, f: F) -> &mut Self
+    pub(crate) fn around_worker<F>(&mut self, f: F) -> &mut Self
     where
         F: Fn(usize, &mut dyn FnMut()) + Send + Sync + 'static,
     {
@@ -127,27 +82,11 @@ impl Builder {
         self
     }
 
-    /// Create the configured `ThreadPool`.
-    ///
-    /// The returned `ThreadPool` instance is ready to spawn tasks.
-    ///
-    /// # Examples
-    ///
-    /// ```
-    /// use tokio::executor::thread_pool::Builder;
-    ///
-    /// let thread_pool = Builder::new()
-    ///     .build();
-    /// ```
-    pub fn build(&self) -> ThreadPool {
-        self.build_with_park(|_| DefaultPark::new())
-    }
-
     /// Create the configured `ThreadPool` with a custom `park` instances.
     ///
     /// The provided closure `build_park` is called once per worker and returns
     /// a `Park` instance that is used by the worker to put itself to sleep.
-    pub fn build_with_park<F, P>(&self, mut build_park: F) -> ThreadPool
+    pub(crate) fn build<F, P>(&self, mut build_park: F) -> ThreadPool
     where
         F: FnMut(usize) -> P,
         P: Park + Send + 'static,
diff --git a/tokio/src/executor/thread_pool/mod.rs b/tokio/src/executor/thread_pool/mod.rs
index c18d8766..0c7ce42a 100644
--- a/tokio/src/executor/thread_pool/mod.rs
+++ b/tokio/src/executor/thread_pool/mod.rs
@@ -1,7 +1,7 @@
 //! Threadpool
 
 mod builder;
-pub use self::builder::Builder;
+pub(crate) use self::builder::Builder;
 
 mod current;
 
@@ -11,15 +11,13 @@ use self::idle::Idle;
 mod owned;
 use self::owned::Owned;
 
-mod park;
-
 mod pool;
-pub use self::pool::ThreadPool;
+pub(crate) use self::pool::ThreadPool;
 
 mod queue;
 
 mod spawner;
-pub use self::spawner::Spawner;
+pub(crate) use self::spawner::Spawner;
 
 mod set;
 
@@ -29,14 +27,13 @@ use self::shared::Shared;
 mod shutdown;
 
 mod worker;
+#[cfg(feature = "blocking")]
+pub(crate) use worker::blocking;
 
 /// Unit tests
 #[cfg(test)]
 mod tests;
 
-#[cfg(feature = "blocking")]
-pub use worker::blocking;
-
 #[cfg(not(loom))]
 const LOCAL_QUEUE_CAPACITY: usize = 256;
 
diff --git a/tokio/src/executor/thread_pool/park.rs b/tokio/src/executor/thread_pool/park.rs
deleted file mode 100644
index 225d21db..00000000
--- a/tokio/src/executor/thread_pool/park.rs
+++ /dev/null
@@ -1,182 +0,0 @@
-use crate::executor::loom::sync::atomic::AtomicUsize;
-use crate::executor::loom::sync::{Arc, Condvar, Mutex};
-use crate::executor::park::{Park, Unpark};
-
-use std::error::Error;
-use std::fmt;
-use std::sync::atomic::Ordering::SeqCst;
-use std::time::Duration;
-
-/// Parks the thread.
-#[derive(Debug)]
-pub(crate) struct DefaultPark {
-    inner: Arc<Inner>,
-}
-
-/// Unparks threads that were parked by `DefaultPark`.
-#[derive(Debug)]
-pub(crate) struct DefaultUnpark {
-    inner: Arc<Inner>,
-}
-
-/// Error returned by [`ParkThread`]
-///
-/// This currently is never returned, but might at some point in the future.
-///
-/// [`ParkThread`]: struct.ParkThread.html
-#[derive(Debug)]
-pub(crate) struct ParkError {
-    _p: (),
-}
-
-const EMPTY: usize = 0;
-const PARKED: usize = 1;
-const NOTIFIED: usize = 2;
-
-#[derive(Debug)]
-struct Inner {
-    state: AtomicUsize,
-    lock: Mutex<()>,
-    cvar: Condvar,
-}
-
-impl DefaultPark {
-    /// Creates a new `DefaultPark` instance.
-    pub(crate) fn new() -> DefaultPark {
-        DefaultPark {
-            inner: Arc::new(Inner {
-                state: AtomicUsize::new(EMPTY),
-                lock: Mutex::new(()),
-                cvar: Condvar::new(),
-            }),
-        }
-    }
-}
-
-impl Park for DefaultPark {
-    type Unpark = DefaultUnpark;
-    type Error = ParkError;
-
-    fn unpark(&self) -> Self::Unpark {
-        let inner = self.inner.clone();
-        DefaultUnpark { inner }
-    }
-
-    fn park(&mut self) -> Result<(), Self::Error> {
-        self.inner.park(None);
-        Ok(())
-    }
-
-    fn park_timeout(&mut self, duration: Duration) -> Result<(), Self::Error> {
-        self.inner.park(Some(duration));
-        Ok(())
-    }
-}
-
-impl Unpark for DefaultUnpark {
-    fn unpark(&self) {
-        self.inner.unpark();
-    }
-}
-
-impl fmt::Display for ParkError {
-    fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
-        write!(fmt, "unknown park error")
-    }
-}
-
-impl Error for ParkError {}
-
-impl Inner {
-    fn park(&self, timeout: Option<Duration>) {
-        // If we were previously notified then we consume this notification and return quickly.
-        if self
-            .state
-            .compare_exchange(NOTIFIED, EMPTY, SeqCst, SeqCst)
-            .is_ok()
-        {
-            return;
-        }
-
-        // If the timeout is zero, then there is no need to actually block.
-        if let Some(ref dur) = timeout {
-            if *dur == Duration::from_millis(0) {
-                return;
-            }
-        }
-
-        // Otherwise we need to coordinate going to sleep.
-        let mut _m = self.lock.lock().unwrap();
-
-        match self.state.compare_exchange(EMPTY, PARKED, SeqCst, SeqCst) {
-            Ok(_) => {}
-            // Consume this notification to avoid spurious wakeups in the next park.
-            Err(NOTIFIED) => {
-                // We must read `state` here, even though we know it will be `NOTIFIED`. This is
-                // because `unpark` may have been called again since we read `NOTIFIED` in the
-                // `compare_exchange` above. We must perform an acquire operation that synchronizes
-                // with that `unpark` to observe any writes it made before the call to `unpark`. To
-                // do that we must read from the write it made to `state`.
-                let old = self.state.swap(EMPTY, SeqCst);
-                assert_eq!(old, NOTIFIED, "park state changed unexpectedly");
-                return;
-            }
-            Err(n) => panic!("inconsistent park_timeout state: {}", n),
-        }
-
-        match timeout {
-            None => {
-                loop {
-                    // Block the current thread on the conditional variable.
-                    _m = self.cvar.wait(_m).unwrap();
-
-                    if self
-                        .state
-                        .compare_exchange(NOTIFIED, EMPTY, SeqCst, SeqCst)
-                        .is_ok()
-                    {
-                        return; // got a notification
-                    }
-
-                    // spurious wakeup, go back to sleep
-                }
-            }
-            Some(timeout) => {
-                // Wait with a timeout, and if we spuriously wake up or otherwise wake up from a
-                // notification we just want to unconditionally set `state` back to `EMPTY`, either
-                // consuming a notification or un-flagging ourselves as parked.
-                _m = self.cvar.wait_timeout(_m, timeout).unwrap().0;
-
-                match self.state.swap(EMPTY, SeqCst) {
-                    NOTIFIED => {} // got a notification
-                    PARKED => {}   // no notification
-                    n => panic!("inconsistent park_timeout state: {}", n),
-                }
-            }
-        }
-    }
-
-    fn unpark(&self) {
-        // To ensure the unparked thread will observe any writes we made before this call, we must
-        // perform a release operation that `park` can synchronize with. To do that we must write
-        // `NOTIFIED` even if `state` is already `NOTIFIED`. That is why this must be a swap rather
-        // than a compare-and-swap that returns if it reads `NOTIFIED` on failure.
-        match self.state.swap(NOTIFIED, SeqCst) {
-            EMPTY => return,    // no one was waiting
-            NOTIFIED => return, // already unparked
-            PARKED => {}        // gotta go wake someone up
-            n => panic!("inconsistent state in unpark: {}", n),
-        }
-
-        // There is a period between when the parked thread sets `state` to `PARKED` (or last
-        // checked `state` in the case of a spurious wakeup) and when it actually waits on `cvar`.
-        // If we were to notify during this period it would be ignored and then when the parked
-        // thread went to sleep it would never wake up. Fortunately, it has `lock` locked at this
-        // stage so we can acquire `lock` to wait until it is ready to receive the notification.
-        //
-        // Releasing `lock` before the call to `notify_one` means that when the parked thread wakes
-        // it doesn't get woken only to have to wait for us to release `lock`.
-        drop(self.lock.lock());
-        self.cvar.notify_one();
-    }
-}
diff --git a/tokio/src/executor/thread_pool/pool.rs b/tokio/src/executor/thread_pool/pool.rs
index 67235eae..d3219d87 100644
--- a/tokio/src/executor/thread_pool/pool.rs
+++ b/tokio/src/executor/thread_pool/pool.rs
@@ -1,12 +1,12 @@
 use crate::executor::blocking::PoolWaiter;
 use crate::executor::task::JoinHandle;
-use crate::executor::thread_pool::{shutdown, Builder, Spawner};
+use crate::executor::thread_pool::{shutdown, Spawner};
 
 use std::fmt;
 use std::future::Future;
 
 /// Work-stealing based thread pool for executing futures.
-pub struct ThreadPool {
+pub(crate) struct ThreadPool {
     spawner: Spawner,
 
     /// Shutdown waiter
@@ -17,11 +17,6 @@ pub struct ThreadPool {
 }
 
 impl ThreadPool {
-    /// Create a new ThreadPool with default configuration
-    pub fn new() -> ThreadPool {
-        Builder::new().build()
-    }
-
     pub(super) fn from_parts(
         spawner: Spawner,
         shutdown_rx: shutdown::Receiver,
@@ -38,12 +33,12 @@ impl ThreadPool {
     ///
     /// The `Spawner` handle can be cloned and enables spawning tasks from other
     /// threads.
-    pub fn spawner(&self) -> &Spawner {
+    pub(crate) fn spawner(&self) -> &Spawner {
         &self.spawner
     }
 
     /// Spawn a task
-    pub fn spawn<F>(&self, future: F) -> JoinHandle<F::Output>
+    pub(crate) fn spawn<F>(&self, future: F) -> JoinHandle<F::Output>
     where
         F: Future + Send + 'static,
         F::Output: Send + 'static,
@@ -55,7 +50,7 @@ impl ThreadPool {
     ///
     /// The future will execute on the current thread, but all spawned tasks
     /// will be executed on the thread pool.
-    pub fn block_on<F>(&self, future: F) -> F::Output
+    pub(crate) fn block_on<F>(&self, future: F) -> F::Output
     where
         F: Future,
     {
@@ -69,7 +64,7 @@ impl ThreadPool {
     }
 
     /// Shutdown the thread pool.
-    pub fn shutdown_now(&mut self) {
+    pub(crate) fn shutdown_now(&mut self) {
         if self.spawner.workers().close() {
             self.shutdown_rx.wait();
         }
@@ -77,12 +72,6 @@ impl ThreadPool {
     }
 }
 
-impl Default for ThreadPool {
-    fn default() -> ThreadPool {
-        ThreadPool::new()
-    }
-}
-
 impl fmt::Debug for ThreadPool {
     fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
         fmt.debug_struct("ThreadPool").finish()
diff --git a/tokio/src/executor/thread_pool/spawner.rs b/tokio/src/executor/thread_pool/spawner.rs
index b33c7cad..4fdf9594 100644
--- a/tokio/src/executor/thread_pool/spawner.rs
+++ b/tokio/src/executor/thread_pool/spawner.rs
@@ -19,7 +19,7 @@ use std::future::Future;
 ///
 /// [`ThreadPool::spawner`]: struct.ThreadPool.html#method.spawner
 #[derive(Clone)]
-pub struct Spawner {
+pub(crate) struct Spawner {
     workers: Arc<worker::Set<Box<dyn Unpark>>>,
 }
 
@@ -29,7 +29,7 @@ impl Spawner {
     }
 
     /// Spawn a future onto the thread pool
-    pub fn spawn<F>(&self, future: F) -> JoinHandle<F::Output>
+    pub(crate) fn spawn<F>(&self, future: F) -> JoinHandle<F::Output>
     where
         F: Future + Send + 'static,
         F::Output: Send + 'static,
diff --git a/tokio/src/executor/thread_pool/tests/loom_pool.rs b/tokio/src/executor/thread_pool/tests/loom_pool.rs
index 26c794ec..6b2b5c30 100644
--- a/tokio/src/executor/thread_pool/tests/loom_pool.rs
+++ b/tokio/src/executor/thread_pool/tests/loom_pool.rs
@@ -1,16 +1,20 @@
 use crate::executor::loom::sync::atomic::Ordering::{Acquire, Relaxed, Release};
 use crate::executor::loom::sync::atomic::{AtomicBool, AtomicUsize};
 use crate::executor::loom::sync::{Arc, Mutex};
+use crate::executor::park::{Park, Unpark};
 use crate::executor::tests::loom_oneshot as oneshot;
-use crate::executor::thread_pool::{self, Builder, ThreadPool};
+use crate::executor::thread_pool::{self, Builder};
 use crate::spawn;
 
+use loom::sync::Notify;
+
 use std::future::Future;
+use std::time::Duration;
 
 #[test]
 fn pool_multi_spawn() {
     loom::model(|| {
-        let pool = ThreadPool::new();
+        let pool = Builder::new().build(|_| LoomPark::new());
 
         let c1 = Arc::new(AtomicUsize::new(0));
 
@@ -44,7 +48,7 @@ fn pool_multi_spawn() {
 #[test]
 fn only_blocking() {
     loom::model(|| {
-        let mut pool = Builder::new().num_threads(1).build();
+        let mut pool = Builder::new().num_threads(1).build(|_| LoomPark::new());
         let (block_tx, block_rx) = oneshot::channel();
 
         pool.spawn(async move {
@@ -62,7 +66,7 @@ fn only_blocking() {
 fn blocking_and_regular() {
     const NUM: usize = 3;
     loom::model(|| {
-        let mut pool = Builder::new().num_threads(1).build();
+        let mut pool = Builder::new().num_threads(1).build(|_| LoomPark::new());
         let cnt = Arc::new(AtomicUsize::new(0));
 
         let (block_tx, block_rx) = oneshot::channel();
@@ -96,7 +100,7 @@ fn blocking_and_regular() {
 #[test]
 fn pool_multi_notify() {
     loom::model(|| {
-        let pool = ThreadPool::new();
+        let pool = Builder::