Merge pull request #396 from embassy-rs/channel-fixes

embassy/channel: several improvements

5 files changed, 116 insertions, 185 deletions

diff --git a/embassy/Cargo.toml b/embassy/Cargo.toml
index 0a8ab4434..ae06bc198 100644
--- a/embassy/Cargo.toml
+++ b/embassy/Cargo.toml
@@ -42,6 +42,7 @@ embassy-traits  = { version = "0.1.0", path = "../embassy-traits"}
 atomic-polyfill  = "0.1.3"
 critical-section = "0.2.1"
 embedded-hal = "0.2.6"
+heapless = "0.7.5"
 
 [dev-dependencies]
 embassy = { path = ".", features = ["executor-agnostic"] }
diff --git a/embassy/src/blocking_mutex/kind.rs b/embassy/src/blocking_mutex/kind.rs
new file mode 100644
index 000000000..30fc90497
--- /dev/null
+++ b/embassy/src/blocking_mutex/kind.rs
@@ -0,0 +1,19 @@
+use super::{CriticalSectionMutex, Mutex, NoopMutex, ThreadModeMutex};
+
+pub trait MutexKind {
+    type Mutex<T>: Mutex<Data = T>;
+}
+
+pub enum CriticalSection {}
+impl MutexKind for CriticalSection {
+    type Mutex<T> = CriticalSectionMutex<T>;
+}
+
+pub enum ThreadMode {}
+impl MutexKind for ThreadMode {
+    type Mutex<T> = ThreadModeMutex<T>;
+}
+pub enum Noop {}
+impl MutexKind for Noop {
+    type Mutex<T> = NoopMutex<T>;
+}
diff --git a/embassy/src/blocking_mutex/mod.rs b/embassy/src/blocking_mutex/mod.rs
index d112d2ede..641a1ed93 100644
--- a/embassy/src/blocking_mutex/mod.rs
+++ b/embassy/src/blocking_mutex/mod.rs
@@ -1,5 +1,7 @@
 //! Blocking mutex (not async)
 
+pub mod kind;
+
 use core::cell::UnsafeCell;
 use critical_section::CriticalSection;
 
@@ -13,7 +15,7 @@ pub trait Mutex {
     fn new(data: Self::Data) -> Self;
 
     /// Creates a critical section and grants temporary access to the protected data.
-    fn lock<R>(&mut self, f: impl FnOnce(&Self::Data) -> R) -> R;
+    fn lock<R>(&self, f: impl FnOnce(&Self::Data) -> R) -> R;
 }
 
 /// A "mutex" based on critical sections
@@ -55,7 +57,7 @@ impl<T> Mutex for CriticalSectionMutex<T> {
         Self::new(data)
     }
 
-    fn lock<R>(&mut self, f: impl FnOnce(&Self::Data) -> R) -> R {
+    fn lock<R>(&self, f: impl FnOnce(&Self::Data) -> R) -> R {
         critical_section::with(|cs| f(self.borrow(cs)))
     }
 }
@@ -102,7 +104,7 @@ impl<T> Mutex for ThreadModeMutex<T> {
         Self::new(data)
     }
 
-    fn lock<R>(&mut self, f: impl FnOnce(&Self::Data) -> R) -> R {
+    fn lock<R>(&self, f: impl FnOnce(&Self::Data) -> R) -> R {
         f(self.borrow())
     }
 }
@@ -155,7 +157,7 @@ impl<T> Mutex for NoopMutex<T> {
         Self::new(data)
     }
 
-    fn lock<R>(&mut self, f: impl FnOnce(&Self::Data) -> R) -> R {
+    fn lock<R>(&self, f: impl FnOnce(&Self::Data) -> R) -> R {
         f(self.borrow())
     }
 }
diff --git a/embassy/src/channel/mpsc.rs b/embassy/src/channel/mpsc.rs
index b20d48a95..9a57c0b19 100644
--- a/embassy/src/channel/mpsc.rs
+++ b/embassy/src/channel/mpsc.rs
@@ -37,19 +37,18 @@
 //!
 //! This channel and its associated types were derived from https://docs.rs/tokio/0.1.22/tokio/sync/mpsc/fn.channel.html
 
-use core::cell::UnsafeCell;
+use core::cell::RefCell;
 use core::fmt;
-use core::marker::PhantomData;
-use core::mem::MaybeUninit;
 use core::pin::Pin;
-use core::ptr;
 use core::task::Context;
 use core::task::Poll;
 use core::task::Waker;
 
 use futures::Future;
+use heapless::Deque;
 
-use crate::blocking_mutex::{CriticalSectionMutex, Mutex, NoopMutex, ThreadModeMutex};
+use crate::blocking_mutex::kind::MutexKind;
+use crate::blocking_mutex::Mutex;
 use crate::waitqueue::WakerRegistration;
 
 /// Send values to the associated `Receiver`.
@@ -57,36 +56,19 @@ use crate::waitqueue::WakerRegistration;
 /// Instances are created by the [`split`](split) function.
 pub struct Sender<'ch, M, T, const N: usize>
 where
-    M: Mutex<Data = ()>,
+    M: MutexKind,
 {
-    channel_cell: &'ch UnsafeCell<ChannelCell<M, T, N>>,
+    channel: &'ch Channel<M, T, N>,
 }
 
-// Safe to pass the sender around
-unsafe impl<'ch, M, T, const N: usize> Send for Sender<'ch, M, T, N> where M: Mutex<Data = ()> + Sync
-{}
-unsafe impl<'ch, M, T, const N: usize> Sync for Sender<'ch, M, T, N> where M: Mutex<Data = ()> + Sync
-{}
-
 /// Receive values from the associated `Sender`.
 ///
 /// Instances are created by the [`split`](split) function.
 pub struct Receiver<'ch, M, T, const N: usize>
 where
-    M: Mutex<Data = ()>,
-{
-    channel_cell: &'ch UnsafeCell<ChannelCell<M, T, N>>,
-    _receiver_consumed: &'ch mut PhantomData<()>,
-}
-
-// Safe to pass the receiver around
-unsafe impl<'ch, M, T, const N: usize> Send for Receiver<'ch, M, T, N> where
-    M: Mutex<Data = ()> + Sync
-{
-}
-unsafe impl<'ch, M, T, const N: usize> Sync for Receiver<'ch, M, T, N> where
-    M: Mutex<Data = ()> + Sync
+    M: MutexKind,
 {
+    channel: &'ch Channel<M, T, N>,
 }
 
 /// Splits a bounded mpsc channel into a `Sender` and `Receiver`.
@@ -117,16 +99,11 @@ pub fn split<M, T, const N: usize>(
     channel: &mut Channel<M, T, N>,
 ) -> (Sender<M, T, N>, Receiver<M, T, N>)
 where
-    M: Mutex<Data = ()>,
+    M: MutexKind,
 {
-    let sender = Sender {
-        channel_cell: &channel.channel_cell,
-    };
-    let receiver = Receiver {
-        channel_cell: &channel.channel_cell,
-        _receiver_consumed: &mut channel.receiver_consumed,
-    };
-    Channel::lock(&channel.channel_cell, |c| {
+    let sender = Sender { channel };
+    let receiver = Receiver { channel };
+    channel.lock(|c| {
         c.register_receiver();
         c.register_sender();
     });
@@ -135,7 +112,7 @@ where
 
 impl<'ch, M, T, const N: usize> Receiver<'ch, M, T, N>
 where
-    M: Mutex<Data = ()>,
+    M: MutexKind,
 {
     /// Receives the next value for this receiver.
     ///
@@ -155,7 +132,7 @@ where
     /// [`close`]: Self::close
     pub fn recv<'m>(&'m mut self) -> RecvFuture<'m, M, T, N> {
         RecvFuture {
-            channel_cell: self.channel_cell,
+            channel: self.channel,
         }
     }
 
@@ -164,7 +141,7 @@ where
     /// This method will either receive a message from the channel immediately or return an error
     /// if the channel is empty.
     pub fn try_recv(&self) -> Result<T, TryRecvError> {
-        Channel::lock(self.channel_cell, |c| c.try_recv())
+        self.channel.lock(|c| c.try_recv())
     }
 
     /// Closes the receiving half of a channel without dropping it.
@@ -178,56 +155,45 @@ where
     /// until those are released.
     ///
     pub fn close(&mut self) {
-        Channel::lock(self.channel_cell, |c| c.close())
+        self.channel.lock(|c| c.close())
     }
 }
 
 impl<'ch, M, T, const N: usize> Drop for Receiver<'ch, M, T, N>
 where
-    M: Mutex<Data = ()>,
+    M: MutexKind,
 {
     fn drop(&mut self) {
-        Channel::lock(self.channel_cell, |c| c.deregister_receiver())
+        self.channel.lock(|c| c.deregister_receiver())
     }
 }
 
 pub struct RecvFuture<'ch, M, T, const N: usize>
 where
-    M: Mutex<Data = ()>,
+    M: MutexKind,
 {
-    channel_cell: &'ch UnsafeCell<ChannelCell<M, T, N>>,
+    channel: &'ch Channel<M, T, N>,
 }
 
 impl<'ch, M, T, const N: usize> Future for RecvFuture<'ch, M, T, N>
 where
-    M: Mutex<Data = ()>,
+    M: MutexKind,
 {
     type Output = Option<T>;
 
     fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<T>> {
-        Channel::lock(self.channel_cell, |c| {
-            match c.try_recv_with_context(Some(cx)) {
+        self.channel
+            .lock(|c| match c.try_recv_with_context(Some(cx)) {
                 Ok(v) => Poll::Ready(Some(v)),
                 Err(TryRecvError::Closed) => Poll::Ready(None),
                 Err(TryRecvError::Empty) => Poll::Pending,
-            }
-        })
+            })
     }
 }
 
-// Safe to pass the receive future around since it locks channel whenever polled
-unsafe impl<'ch, M, T, const N: usize> Send for RecvFuture<'ch, M, T, N> where
-    M: Mutex<Data = ()> + Sync
-{
-}
-unsafe impl<'ch, M, T, const N: usize> Sync for RecvFuture<'ch, M, T, N> where
-    M: Mutex<Data = ()> + Sync
-{
-}
-
 impl<'ch, M, T, const N: usize> Sender<'ch, M, T, N>
 where
-    M: Mutex<Data = ()>,
+    M: MutexKind,
 {
     /// Sends a value, waiting until there is capacity.
     ///
@@ -249,7 +215,7 @@ where
     /// [`Receiver`]: Receiver
     pub fn send(&self, message: T) -> SendFuture<'ch, M, T, N> {
         SendFuture {
-            sender: self.clone(),
+            channel: self.channel,
             message: Some(message),
         }
     }
@@ -275,7 +241,7 @@ where
     /// [`channel`]: channel
     /// [`close`]: Receiver::close
     pub fn try_send(&self, message: T) -> Result<(), TrySendError<T>> {
-        Channel::lock(self.channel_cell, |c| c.try_send(message))
+        self.channel.lock(|c| c.try_send(message))
     }
 
     /// Completes when the receiver has dropped.
@@ -284,7 +250,7 @@ where
     /// values is canceled and immediately stop doing work.
     pub async fn closed(&self) {
         CloseFuture {
-            sender: self.clone(),
+            channel: self.channel,
         }
         .await
     }
@@ -296,29 +262,27 @@ where
     /// [`Receiver`]: crate::sync::mpsc::Receiver
     /// [`Receiver::close`]: crate::sync::mpsc::Receiver::close
     pub fn is_closed(&self) -> bool {
-        Channel::lock(self.channel_cell, |c| c.is_closed())
+        self.channel.lock(|c| c.is_closed())
     }
 }
 
 pub struct SendFuture<'ch, M, T, const N: usize>
 where
-    M: Mutex<Data = ()>,
+    M: MutexKind,
 {
-    sender: Sender<'ch, M, T, N>,
+    channel: &'ch Channel<M, T, N>,
     message: Option<T>,
 }
 
 impl<'ch, M, T, const N: usize> Future for SendFuture<'ch, M, T, N>
 where
-    M: Mutex<Data = ()>,
+    M: MutexKind,
 {
     type Output = Result<(), SendError<T>>;
 
     fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
         match self.message.take() {
-            Some(m) => match Channel::lock(self.sender.channel_cell, |c| {
-                c.try_send_with_context(m, Some(cx))
-            }) {
+            Some(m) => match self.channel.lock(|c| c.try_send_with_context(m, Some(cx))) {
                 Ok(..) => Poll::Ready(Ok(())),
                 Err(TrySendError::Closed(m)) => Poll::Ready(Err(SendError(m))),
                 Err(TrySendError::Full(m)) => {
@@ -331,25 +295,23 @@ where
     }
 }
 
-impl<'ch, M, T, const N: usize> Unpin for SendFuture<'ch, M, T, N> where M: Mutex<Data = ()> {}
+impl<'ch, M, T, const N: usize> Unpin for SendFuture<'ch, M, T, N> where M: MutexKind {}
 
 struct CloseFuture<'ch, M, T, const N: usize>
 where
-    M: Mutex<Data = ()>,
+    M: MutexKind,
 {
-    sender: Sender<'ch, M, T, N>,
+    channel: &'ch Channel<M, T, N>,
 }
 
 impl<'ch, M, T, const N: usize> Future for CloseFuture<'ch, M, T, N>
 where
-    M: Mutex<Data = ()>,
+    M: MutexKind,
 {
     type Output = ();
 
     fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
-        if Channel::lock(self.sender.channel_cell, |c| {
-            c.is_closed_with_context(Some(cx))
-        }) {
+        if self.channel.lock(|c| c.is_closed_with_context(Some(cx))) {
             Poll::Ready(())
         } else {
             Poll::Pending
@@ -359,22 +321,21 @@ where
 
 impl<'ch, M, T, const N: usize> Drop for Sender<'ch, M, T, N>
 where
-    M: Mutex<Data = ()>,
+    M: MutexKind,
 {
     fn drop(&mut self) {
-        Channel::lock(self.channel_cell, |c| c.deregister_sender())
+        self.channel.lock(|c| c.deregister_sender())
     }
 }
 
 impl<'ch, M, T, const N: usize> Clone for Sender<'ch, M, T, N>
 where
-    M: Mutex<Data = ()>,
+    M: MutexKind,
 {
-    #[allow(clippy::clone_double_ref)]
     fn clone(&self) -> Self {
-        Channel::lock(self.channel_cell, |c| c.register_sender());
+        self.channel.lock(|c| c.register_sender());
         Sender {
-            channel_cell: self.channel_cell.clone(),
+            channel: self.channel,
         }
     }
 }
@@ -446,10 +407,7 @@ impl<T> defmt::Format for TrySendError<T> {
 }
 
 struct ChannelState<T, const N: usize> {
-    buf: [MaybeUninit<UnsafeCell<T>>; N],
-    read_pos: usize,
-    write_pos: usize,
-    full: bool,
+    queue: Deque<T, N>,
     closed: bool,
     receiver_registered: bool,
     senders_registered: u32,
@@ -458,14 +416,9 @@ struct ChannelState<T, const N: usize> {
 }
 
 impl<T, const N: usize> ChannelState<T, N> {
-    const INIT: MaybeUninit<UnsafeCell<T>> = MaybeUninit::uninit();
-
     const fn new() -> Self {
         ChannelState {
-            buf: [Self::INIT; N],
-            read_pos: 0,
-            write_pos: 0,
-            full: false,
+            queue: Deque::new(),
             closed: false,
             receiver_registered: false,
             senders_registered: 0,
@@ -479,17 +432,16 @@ impl<T, const N: usize> ChannelState<T, N> {
     }
 
     fn try_recv_with_context(&mut self, cx: Option<&mut Context<'_>>) -> Result<T, TryRecvError> {
-        if self.read_pos != self.write_pos || self.full {
-            if self.full {
-                self.full = false;
-                self.senders_waker.wake();
-            }
-            let message = unsafe { (self.buf[self.read_pos]).assume_init_mut().get().read() };
-            self.read_pos = (self.read_pos + 1) % self.buf.len();
+        if self.queue.is_full() {
+            self.senders_waker.wake();
+        }
+
+        if let Some(message) = self.queue.pop_front() {
             Ok(message)
         } else if !self.closed {
-            cx.into_iter()
-                .for_each(|cx| self.set_receiver_waker(&cx.waker()));
+            if let Some(cx) = cx {
+                self.set_receiver_waker(cx.waker());
+            }
             Err(TryRecvError::Empty)
         } else {
             Err(TryRecvError::Closed)
@@ -505,22 +457,21 @@ impl<T, const N: usize> ChannelState<T, N> {
         message: T,
         cx: Option<&mut Context<'_>>,
     ) -> Result<(), TrySendError<T>> {
-        if !self.closed {
-            if !self.full {
-                self.buf[self.write_pos] = MaybeUninit::new(message.into());
-                self.write_pos = (self.write_pos + 1) % self.buf.len();
-                if self.write_pos == self.read_pos {
-                    self.full = true;
-                }
+        if self.closed {
+            return Err(TrySendError::Closed(message));
+        }
+
+        match self.queue.push_back(message) {
+            Ok(()) => {
                 self.receiver_waker.wake();
+
                 Ok(())
-            } else {
+            }
+            Err(message) => {
                 cx.into_iter()
                     .for_each(|cx| self.set_senders_waker(&cx.waker()));
                 Err(TrySendError::Full(message))
             }
-        } else {
-            Err(TrySendError::Closed(message))
         }
     }
 
@@ -585,16 +536,6 @@ impl<T, const N: usize> ChannelState<T, N> {
     }
 }
 
-impl<T, const N: usize> Drop for ChannelState<T, N> {
-    fn drop(&mut self) {
-        while self.read_pos != self.write_pos || self.full {
-            self.full = false;
-            unsafe { ptr::drop_in_place(self.buf[self.read_pos].as_mut_ptr()) };
-            self.read_pos = (self.read_pos + 1) % N;
-        }
-    }
-}
-
 /// A a bounded mpsc channel for communicating between asynchronous tasks
 /// with backpressure.
 ///
@@ -605,61 +546,35 @@ impl<T, const N: usize> Drop for ChannelState<T, N> {
 /// All data sent will become available in the same order as it was sent.
 pub struct Channel<M, T, const N: usize>
 where
-    M: Mutex<Data = ()>,
+    M: MutexKind,
 {
-    channel_cell: UnsafeCell<ChannelCell<M, T, N>>,
-    receiver_consumed: PhantomData<()>,
+    inner: M::Mutex<RefCell<ChannelState<T, N>>>,
 }
 
-struct ChannelCell<M, T, const N: usize>
-where
-    M: Mutex<Data = ()>,
-{
-    mutex: M,
-    state: ChannelState<T, N>,
-}
-
-pub type WithCriticalSections = CriticalSectionMutex<()>;
-
-pub type WithThreadModeOnly = ThreadModeMutex<()>;
-
-pub type WithNoThreads = NoopMutex<()>;
-
 impl<M, T, const N: usize> Channel<M, T, N>
 where
-    M: Mutex<Data = ()>,
+    M: MutexKind,
 {
     /// Establish a new bounded channel. For example, to create one with a NoopMutex:
     ///
     /// ```
     /// use embassy::channel::mpsc;
-    /// use embassy::channel::mpsc::{Channel, WithNoThreads};
+    /// use embassy::blocking_mutex::kind::Noop;
+    /// use embassy::channel::mpsc::Channel;
     ///
     /// // Declare a bounded channel of 3 u32s.
-    /// let mut channel = Channel::<WithNoThreads, u32, 3>::new();
+    /// let mut channel = Channel::<Noop, u32, 3>::new();
     /// // once we have a channel, obtain its sender and receiver
     /// let (sender, receiver) = mpsc::split(&mut channel);
     /// ```
     pub fn new() -> Self {
-        let mutex = M::new(());
-        let state = ChannelState::new();
-        let channel_cell = ChannelCell { mutex, state };
-        Channel {
-            channel_cell: UnsafeCell::new(channel_cell),
-            receiver_consumed: PhantomData,
+        Self {
+            inner: M::Mutex::new(RefCell::new(ChannelState::new())),
         }
     }
 
-    fn lock<R>(
-        channel_cell: &UnsafeCell<ChannelCell<M, T, N>>,
-        f: impl FnOnce(&mut ChannelState<T, N>) -> R,
-    ) -> R {
-        unsafe {
-            let channel_cell = &mut *(channel_cell.get());
-            let mutex = &mut channel_cell.mutex;
-            let mut state = &mut channel_cell.state;
-            mutex.lock(|_| f(&mut state))
-        }
+    fn lock<R>(&self, f: impl FnOnce(&mut ChannelState<T, N>) -> R) -> R {
+        self.inner.lock(|rc| f(&mut *rc.borrow_mut()))
     }
 }
 
@@ -671,20 +586,13 @@ mod tests {
     use futures_executor::ThreadPool;
     use futures_timer::Delay;
 
+    use crate::blocking_mutex::kind::{CriticalSection, Noop};
     use crate::util::Forever;
 
     use super::*;
 
     fn capacity<T, const N: usize>(c: &ChannelState<T, N>) -> usize {
-        if !c.full {
-            if c.write_pos > c.read_pos {
-                (c.buf.len() - c.write_pos) + c.read_pos
-            } else {
-                (c.buf.len() - c.read_pos) + c.write_pos
-            }
-        } else {
-            0
-        }
+        c.queue.capacity() - c.queue.len()
     }
 
     #[test]
@@ -747,7 +655,7 @@ mod tests {
 
     #[test]
     fn simple_send_and_receive() {
-        let mut c = Channel::<WithNoThreads, u32, 3>::new();
+        let mut c = Channel::<Noop, u32, 3>::new();
         let (s, r) = split(&mut c);
         assert!(s.clone().try_send(1).is_ok());
         assert_eq!(r.try_recv().unwrap(), 1);
@@ -755,7 +663,7 @@ mod tests {
 
     #[test]
     fn should_close_without_sender() {
-        let mut c = Channel::<WithNoThreads, u32, 3>::new();
+        let mut c = Channel::<Noop, u32, 3>::new();
         let (s, r) = split(&mut c);
         drop(s);
         match r.try_recv() {
@@ -766,7 +674,7 @@ mod tests {
 
     #[test]
     fn should_close_once_drained() {
-        let mut c = Channel::<WithNoThreads, u32, 3>::new();
+        let mut c = Channel::<Noop, u32, 3>::new();
         let (s, r) = split(&mut c);
         assert!(s.try_send(1).is_ok());
         drop(s);
@@ -779,7 +687,7 @@ mod tests {
 
     #[test]
     fn should_reject_send_when_receiver_dropped() {
-        let mut c = Channel::<WithNoThreads, u32, 3>::new();
+        let mut c = Channel::<Noop, u32, 3>::new();
         let (s, r) = split(&mut c);
         drop(r);
         match s.try_send(1) {
@@ -790,7 +698,7 @@ mod tests {
 
     #[test]
     fn should_reject_send_when_channel_closed() {
-        let mut c = Channel::<WithNoThreads, u32, 3>::new();
+        let mut c = Channel::<Noop, u32, 3>::new();
         let (s, mut r) = split(&mut c);
         assert!(s.try_send(1).is_ok());
         r.close();
@@ -806,7 +714,7 @@ mod tests {
     async fn receiver_closes_when_sender_dropped_async() {
         let executor = ThreadPool::new().unwrap();
 
-        static CHANNEL: Forever<Channel<WithCriticalSections, u32, 3>> = Forever::new();
+        static CHANNEL: Forever<Channel<CriticalSection, u32, 3>> = Forever::new();
         let c = CHANNEL.put(Channel::new());
         let (s, mut r) = split(c);
         assert!(executor
@@ -821,7 +729,7 @@ mod tests {
     async fn receiver_receives_given_try_send_async() {
         let executor = ThreadPool::new().unwrap();
 
-        static CHANNEL: Forever<Channel<WithCriticalSections, u32, 3>> = Forever::new();
+        static CHANNEL: Forever<Channel<CriticalSection, u32, 3>> = Forever::new();
         let c = CHANNEL.put(Channel::new());
         let (s, mut r) = split(c);
         assert!(executor
@@ -834,7 +742,7 @@ mod tests {
 
     #[futures_test::test]
     async fn sender_send_completes_if_capacity() {
-        let mut c = Channel::<WithCriticalSections, u32, 1>::new();
+        let mut c = Channel::<CriticalSection, u32, 1>::new();
         let (s, mut r) = split(&mut c);
         assert!(s.send(1).await.is_ok());
         assert_eq!(r.recv().await, Some(1));
@@ -842,7 +750,7 @@ mod tests {
 
     #[futures_test::test]
     async fn sender_send_completes_if_closed() {
-        static CHANNEL: Forever<Channel<WithCriticalSections, u32, 1>> = Forever::new();
+        static CHANNEL: Forever<Channel<CriticalSection, u32, 1>> = Forever::new();
         let c = CHANNEL.put(Channel::new());
         let (s, r) = split(c);
         drop(r);
@@ -856,7 +764,7 @@ mod tests {
     async fn senders_sends_wait_until_capacity() {
         let executor = ThreadPool::new().unwrap();
 
-        static CHANNEL: Forever<Channel<WithCriticalSections, u32, 1>> = Forever::new();
+        static CHANNEL: Forever<Channel<CriticalSection, u32, 1>> = Forever::new();
         let c = CHANNEL.put(Channel::new());
         let (s0, mut r) = split(c);
         assert!(s0.try_send(1).is_ok());
@@ -876,7 +784,7 @@ mod tests {
 
     #[futures_test::test]
     async fn sender_close_completes_if_closing() {
-        static CHANNEL: Forever<Channel<WithCriticalSections, u32, 1>> = Forever::new();
+        static CHANNEL: Forever<Channel<CriticalSection, u32, 1>> = Forever::new();
         let c = CHANNEL.put(Channel::new());
         let (s, mut r) = split(c);
         r.close();
@@ -885,7 +793,7 @@ mod tests {
 
     #[futures_test::test]
     async fn sender_close_completes_if_closed() {
-        static CHANNEL: Forever<Channel<WithCriticalSections, u32, 1>> = Forever::new();
+        static CHANNEL: Forever<Channel<CriticalSection, u32, 1>> = Forever::new();
         let c = CHANNEL.put(Channel::new());
         let (s, r) = split(c);
         drop(r);
diff --git a/examples/nrf/src/bin/mpsc.rs b/examples/nrf/src/bin/mpsc.rs
index 79fa3dfb9..c85b7c282 100644
--- a/examples/nrf/src/bin/mpsc.rs
+++ b/examples/nrf/src/bin/mpsc.rs
@@ -6,7 +6,8 @@
 mod example_common;
 
 use defmt::unwrap;
-use embassy::channel::mpsc::{self, Channel, Sender, TryRecvError, WithNoThreads};
+use embassy::blocking_mutex::kind::Noop;
+use embassy::channel::mpsc::{self, Channel, Sender, TryRecvError};
 use embassy::executor::Spawner;
 use embassy::time::{Duration, Timer};
 use embassy::util::Forever;
@@ -19,10 +20,10 @@ enum LedState {
     Off,
 }
 
-static CHANNEL: Forever<Channel<WithNoThreads, LedState, 1>> = Forever::new();
+static CHANNEL: Forever<Channel<Noop, LedState, 1>> = Forever::new();
 
 #[embassy::task(pool_size = 1)]
-async fn my_task(sender: Sender<'static, WithNoThreads, LedState, 1>) {
+async fn my_task(sender: Sender<'static, Noop, LedState, 1>) {
     loop {
         let _ = sender.send(LedState::On).await;
         Timer::after(Duration::from_secs(1)).await;