blocking_mutex: refactor to work on stable. No GATs, and can be constructed in const.

embassy-nrf/src/time_driver.rs

@@ -2,6 +2,7 @@ use core::cell::Cell;
 use core::sync::atomic::{compiler_fence, AtomicU32, AtomicU8, Ordering};
 use core::{mem, ptr};
 use critical_section::CriticalSection;
+use embassy::blocking_mutex::raw::CriticalSectionRawMutex;
 use embassy::blocking_mutex::CriticalSectionMutex as Mutex;
 use embassy::interrupt::{Interrupt, InterruptExt};
 use embassy::time::driver::{AlarmHandle, Driver};
@@ -94,7 +95,7 @@ const ALARM_STATE_NEW: AlarmState = AlarmState::new();
 embassy::time_driver_impl!(static DRIVER: RtcDriver = RtcDriver {
     period: AtomicU32::new(0),
     alarm_count: AtomicU8::new(0),
-    alarms: Mutex::new([ALARM_STATE_NEW; ALARM_COUNT]),
+    alarms: Mutex::const_new(CriticalSectionRawMutex::new(), [ALARM_STATE_NEW; ALARM_COUNT]),
 });
 
 impl RtcDriver {

embassy-rp/src/timer.rs

@@ -1,7 +1,8 @@
 use atomic_polyfill::{AtomicU8, Ordering};
 use core::cell::Cell;
 use critical_section::CriticalSection;
-use embassy::blocking_mutex::CriticalSectionMutex as Mutex;
+use embassy::blocking_mutex::raw::CriticalSectionRawMutex;
+use embassy::blocking_mutex::Mutex;
 use embassy::interrupt::{Interrupt, InterruptExt};
 use embassy::time::driver::{AlarmHandle, Driver};
 
@@ -20,12 +21,12 @@ const DUMMY_ALARM: AlarmState = AlarmState {
 };
 
 struct TimerDriver {
-    alarms: Mutex<[AlarmState; ALARM_COUNT]>,
+    alarms: Mutex<CriticalSectionRawMutex, [AlarmState; ALARM_COUNT]>,
     next_alarm: AtomicU8,
 }
 
 embassy::time_driver_impl!(static DRIVER: TimerDriver = TimerDriver{
-    alarms:  Mutex::new([DUMMY_ALARM; ALARM_COUNT]),
+    alarms:  Mutex::const_new(CriticalSectionRawMutex::new(), [DUMMY_ALARM; ALARM_COUNT]),
     next_alarm: AtomicU8::new(0),
 });
 

embassy-stm32/src/time_driver.rs

@@ -3,13 +3,15 @@ use core::cell::Cell;
 use core::convert::TryInto;
 use core::sync::atomic::{compiler_fence, Ordering};
 use core::{mem, ptr};
+use embassy::blocking_mutex::raw::CriticalSectionRawMutex;
+use embassy::blocking_mutex::Mutex;
 use embassy::interrupt::InterruptExt;
 use embassy::time::driver::{AlarmHandle, Driver};
 use embassy::time::TICKS_PER_SECOND;
 use stm32_metapac::timer::regs;
 
 use crate::interrupt;
-use crate::interrupt::{CriticalSection, Interrupt, Mutex};
+use crate::interrupt::{CriticalSection, Interrupt};
 use crate::pac::timer::{vals, TimGp16};
 use crate::peripherals;
 use crate::rcc::sealed::RccPeripheral;
@@ -95,7 +97,7 @@ struct RtcDriver {
     period: AtomicU32,
     alarm_count: AtomicU8,
     /// Timestamp at which to fire alarm. u64::MAX if no alarm is scheduled.
-    alarms: Mutex<[AlarmState; ALARM_COUNT]>,
+    alarms: Mutex<CriticalSectionRawMutex, [AlarmState; ALARM_COUNT]>,
 }
 
 const ALARM_STATE_NEW: AlarmState = AlarmState::new();
@@ -103,7 +105,7 @@ const ALARM_STATE_NEW: AlarmState = AlarmState::new();
 embassy::time_driver_impl!(static DRIVER: RtcDriver = RtcDriver {
     period: AtomicU32::new(0),
     alarm_count: AtomicU8::new(0),
-    alarms: Mutex::new([ALARM_STATE_NEW; ALARM_COUNT]),
+    alarms: Mutex::const_new(CriticalSectionRawMutex::new(), [ALARM_STATE_NEW; ALARM_COUNT]),
 });
 
 impl RtcDriver {

embassy/src/blocking_mutex/kind.rs

@@ -1,20 +0,0 @@
-pub trait MutexKind {
-    type Mutex<T>: super::Mutex<Data = T>;
-}
-
-pub enum CriticalSection {}
-impl MutexKind for CriticalSection {
-    type Mutex<T> = super::CriticalSectionMutex<T>;
-}
-
-#[cfg(any(cortex_m, feature = "std"))]
-pub enum ThreadMode {}
-#[cfg(any(cortex_m, feature = "std"))]
-impl MutexKind for ThreadMode {
-    type Mutex<T> = super::ThreadModeMutex<T>;
-}
-
-pub enum Noop {}
-impl MutexKind for Noop {
-    type Mutex<T> = super::NoopMutex<T>;
-}

embassy/src/blocking_mutex/mod.rs

@@ -1,66 +1,106 @@
 //! Blocking mutex (not async)
 
-pub mod kind;
+pub mod raw;
 
+use self::raw::RawMutex;
 use core::cell::UnsafeCell;
-use critical_section::CriticalSection;
 
 /// Any object implementing this trait guarantees exclusive access to the data contained
 /// within the mutex for the duration of the lock.
 /// Adapted from <https://github.com/rust-embedded/mutex-trait>.
-pub trait Mutex {
-    /// Data protected by the mutex.
-    type Data;
+pub struct Mutex<R, T: ?Sized> {
+    // NOTE: `raw` must be FIRST, so when using ThreadModeMutex the "can't drop in non-thread-mode" gets
+    // to run BEFORE dropping `data`.
+    raw: R,
+    data: UnsafeCell<T>,
+}
 
-    fn new(data: Self::Data) -> Self;
+unsafe impl<R: RawMutex + Send, T: ?Sized + Send> Send for Mutex<R, T> {}
+unsafe impl<R: RawMutex + Sync, T: ?Sized + Send> Sync for Mutex<R, T> {}
+
+impl<R: RawMutex, T> Mutex<R, T> {
+    /// Creates a new mutex in an unlocked state ready for use.
+    #[cfg(feature = "nightly")]
+    #[inline]
+    pub const fn new(val: T) -> Mutex<R, T> {
+        Mutex {
+            raw: R::INIT,
+            data: UnsafeCell::new(val),
+        }
+    }
+
+    /// Creates a new mutex in an unlocked state ready for use.
+    #[cfg(not(feature = "nightly"))]
+    #[inline]
+    pub fn new(val: T) -> Mutex<R, T> {
+        Mutex {
+            raw: R::INIT,
+            data: UnsafeCell::new(val),
+        }
+    }
 
     /// Creates a critical section and grants temporary access to the protected data.
-    fn lock<R>(&self, f: impl FnOnce(&Self::Data) -> R) -> R;
+    pub fn lock<U>(&self, f: impl FnOnce(&T) -> U) -> U {
+        self.raw.lock(|| {
+            let ptr = self.data.get() as *const T;
+            let inner = unsafe { &*ptr };
+            f(inner)
+        })
+    }
 }
 
-/// A "mutex" based on critical sections
+impl<R, T> Mutex<R, T> {
+    /// Creates a new mutex based on a pre-existing raw mutex.
     ///
-/// # Safety
+    /// This allows creating a mutex in a constant context on stable Rust.
+    #[inline]
+    pub const fn const_new(raw_mutex: R, val: T) -> Mutex<R, T> {
+        Mutex {
+            raw: raw_mutex,
+            data: UnsafeCell::new(val),
+        }
+    }
+
+    /// Consumes this mutex, returning the underlying data.
+    #[inline]
+    pub fn into_inner(self) -> T {
+        self.data.into_inner()
+    }
+
+    /// Returns a mutable reference to the underlying data.
     ///
-/// **This Mutex is only safe on single-core systems.**
-///
-/// On multi-core systems, a `CriticalSection` **is not sufficient** to ensure exclusive access.
-pub struct CriticalSectionMutex<T> {
-    inner: UnsafeCell<T>,
-}
-
-// NOTE: A `CriticalSectionMutex` can be used as a channel so the protected data must be `Send`
-// to prevent sending non-Sendable stuff (e.g. access tokens) across different
-// execution contexts (e.g. interrupts)
-unsafe impl<T> Sync for CriticalSectionMutex<T> where T: Send {}
-
-impl<T> CriticalSectionMutex<T> {
-    /// Creates a new mutex
-    pub const fn new(value: T) -> Self {
-        CriticalSectionMutex {
-            inner: UnsafeCell::new(value),
-        }
+    /// Since this call borrows the `Mutex` mutably, no actual locking needs to
+    /// take place---the mutable borrow statically guarantees no locks exist.
+    #[inline]
+    pub fn get_mut(&mut self) -> &mut T {
+        unsafe { &mut *self.data.get() }
     }
 }
 
-impl<T> CriticalSectionMutex<T> {
+pub type CriticalSectionMutex<T> = Mutex<raw::CriticalSectionRawMutex, T>;
+pub type NoopMutex<T> = Mutex<raw::NoopRawMutex, T>;
+
+impl<T> Mutex<raw::CriticalSectionRawMutex, T> {
     /// Borrows the data for the duration of the critical section
-    pub fn borrow<'cs>(&'cs self, _cs: CriticalSection<'cs>) -> &'cs T {
-        unsafe { &*self.inner.get() }
+    pub fn borrow<'cs>(&'cs self, _cs: critical_section::CriticalSection<'cs>) -> &'cs T {
+        let ptr = self.data.get() as *const T;
+        unsafe { &*ptr }
     }
 }
 
-impl<T> Mutex for CriticalSectionMutex<T> {
-    type Data = T;
-
-    fn new(data: T) -> Self {
-        Self::new(data)
+impl<T> Mutex<raw::NoopRawMutex, T> {
+    /// Borrows the data
+    pub fn borrow(&self) -> &T {
+        let ptr = self.data.get() as *const T;
+        unsafe { &*ptr }
+    }
 }
 
-    fn lock<R>(&self, f: impl FnOnce(&Self::Data) -> R) -> R {
-        critical_section::with(|cs| f(self.borrow(cs)))
-    }
-}
+// ThreadModeMutex does NOT use the generic mutex from above because it's special:
+// it's Send+Sync even if T: !Send. There's no way to do that without specialization (I think?).
+//
+// There's still a ThreadModeRawMutex for use with the generic Mutex (handy with Channel, for example),
+// but that will require T: Send even though it shouldn't be needed.
 
 #[cfg(any(cortex_m, feature = "std"))]
 pub use thread_mode_mutex::*;
@@ -75,15 +115,15 @@ mod thread_mode_mutex {
     /// **This Mutex is only safe on single-core systems.**
     ///
     /// On multi-core systems, a `ThreadModeMutex` **is not sufficient** to ensure exclusive access.
-    pub struct ThreadModeMutex<T> {
+    pub struct ThreadModeMutex<T: ?Sized> {
         inner: UnsafeCell<T>,
     }
 
     // NOTE: ThreadModeMutex only allows borrowing from one execution context ever: thread mode.
     // Therefore it cannot be used to send non-sendable stuff between execution contexts, so it can
     // be Send+Sync even if T is not Send (unlike CriticalSectionMutex)
-    unsafe impl<T> Sync for ThreadModeMutex<T> {}
-    unsafe impl<T> Send for ThreadModeMutex<T> {}
+    unsafe impl<T: ?Sized> Sync for ThreadModeMutex<T> {}
+    unsafe impl<T: ?Sized> Send for ThreadModeMutex<T> {}
 
     impl<T> ThreadModeMutex<T> {
         /// Creates a new mutex
@@ -92,79 +132,35 @@ mod thread_mode_mutex {
                 inner: UnsafeCell::new(value),
             }
         }
+    }
+
+    impl<T: ?Sized> ThreadModeMutex<T> {
+        pub fn lock<R>(&self, f: impl FnOnce(&T) -> R) -> R {
+            f(self.borrow())
+        }
 
         /// Borrows the data
         pub fn borrow(&self) -> &T {
             assert!(
-                in_thread_mode(),
+                raw::in_thread_mode(),
                 "ThreadModeMutex can only be borrowed from thread mode."
             );
             unsafe { &*self.inner.get() }
         }
     }
 
-    impl<T> Mutex for ThreadModeMutex<T> {
-        type Data = T;
-
-        fn new(data: T) -> Self {
-            Self::new(data)
-        }
-
-        fn lock<R>(&self, f: impl FnOnce(&Self::Data) -> R) -> R {
-            f(self.borrow())
-        }
-    }
-
-    impl<T> Drop for ThreadModeMutex<T> {
+    impl<T: ?Sized> Drop for ThreadModeMutex<T> {
         fn drop(&mut self) {
             // Only allow dropping from thread mode. Dropping calls drop on the inner `T`, so
             // `drop` needs the same guarantees as `lock`. `ThreadModeMutex<T>` is Send even if
             // T isn't, so without this check a user could create a ThreadModeMutex in thread mode,
             // send it to interrupt context and drop it there, which would "send" a T even if T is not Send.
             assert!(
-                in_thread_mode(),
+                raw::in_thread_mode(),
                 "ThreadModeMutex can only be dropped from thread mode."
             );
 
             // Drop of the inner `T` happens after this.
         }
     }
-
-    pub fn in_thread_mode() -> bool {
-        #[cfg(feature = "std")]
-        return Some("main") == std::thread::current().name();
-
-        #[cfg(not(feature = "std"))]
-        return cortex_m::peripheral::SCB::vect_active()
-            == cortex_m::peripheral::scb::VectActive::ThreadMode;
-    }
-}
-
-/// A "mutex" that does nothing and cannot be shared between threads.
-pub struct NoopMutex<T> {
-    inner: T,
-}
-
-impl<T> NoopMutex<T> {
-    pub const fn new(value: T) -> Self {
-        NoopMutex { inner: value }
-    }
-}
-
-impl<T> NoopMutex<T> {
-    pub fn borrow(&self) -> &T {
-        &self.inner
-    }
-}
-
-impl<T> Mutex for NoopMutex<T> {
-    type Data = T;
-
-    fn new(data: T) -> Self {
-        Self::new(data)
-    }
-
-    fn lock<R>(&self, f: impl FnOnce(&Self::Data) -> R) -> R {
-        f(self.borrow())
-    }
 }

embassy/src/blocking_mutex/raw.rs

@@ -0,0 +1,112 @@
+use core::marker::PhantomData;
+
+pub trait RawMutex {
+    const INIT: Self;
+
+    fn lock<R>(&self, f: impl FnOnce() -> R) -> R;
+}
+
+pub struct CriticalSectionRawMutex {
+    _phantom: PhantomData<()>,
+}
+unsafe impl Send for CriticalSectionRawMutex {}
+unsafe impl Sync for CriticalSectionRawMutex {}
+
+impl CriticalSectionRawMutex {
+    pub const fn new() -> Self {
+        Self {
+            _phantom: PhantomData,
+        }
+    }
+}
+
+impl RawMutex for CriticalSectionRawMutex {
+    const INIT: Self = Self::new();
+
+    fn lock<R>(&self, f: impl FnOnce() -> R) -> R {
+        critical_section::with(|_| f())
+    }
+}
+
+// ================
+
+pub struct NoopRawMutex {
+    _phantom: PhantomData<*mut ()>,
+}
+
+unsafe impl Send for NoopRawMutex {}
+
+impl NoopRawMutex {
+    pub const fn new() -> Self {
+        Self {
+            _phantom: PhantomData,
+        }
+    }
+}
+
+impl RawMutex for NoopRawMutex {
+    const INIT: Self = Self::new();
+    fn lock<R>(&self, f: impl FnOnce() -> R) -> R {
+        f()
+    }
+}
+
+// ================
+
+#[cfg(any(cortex_m, feature = "std"))]
+mod thread_mode {
+    use super::*;
+
+    pub struct ThreadModeRawMutex {
+        _phantom: PhantomData<()>,
+    }
+
+    unsafe impl Send for ThreadModeRawMutex {}
+    unsafe impl Sync for ThreadModeRawMutex {}
+
+    impl ThreadModeRawMutex {
+        pub const fn new() -> Self {
+            Self {
+                _phantom: PhantomData,
+            }
+        }
+    }
+
+    impl RawMutex for ThreadModeRawMutex {
+        const INIT: Self = Self::new();
+        fn lock<R>(&self, f: impl FnOnce() -> R) -> R {
+            assert!(
+                in_thread_mode(),
+                "ThreadModeMutex can only be locked from thread mode."
+            );
+
+            f()
+        }
+    }
+
+    impl Drop for ThreadModeRawMutex {
+        fn drop(&mut self) {
+            // Only allow dropping from thread mode. Dropping calls drop on the inner `T`, so
+            // `drop` needs the same guarantees as `lock`. `ThreadModeMutex<T>` is Send even if
+            // T isn't, so without this check a user could create a ThreadModeMutex in thread mode,
+            // send it to interrupt context and drop it there, which would "send" a T even if T is not Send.
+            assert!(
+                in_thread_mode(),
+                "ThreadModeMutex can only be dropped from thread mode."
+            );
+
+            // Drop of the inner `T` happens after this.
+        }
+    }
+
+    pub(crate) fn in_thread_mode() -> bool {
+        #[cfg(feature = "std")]
+        return Some("main") == std::thread::current().name();
+
+        #[cfg(not(feature = "std"))]
+        return cortex_m::peripheral::SCB::vect_active()
+            == cortex_m::peripheral::scb::VectActive::ThreadMode;
+    }
+}
+#[cfg(any(cortex_m, feature = "std"))]
+pub use thread_mode::*;

embassy/src/channel/mpsc.rs

@@ -47,7 +47,7 @@ use core::task::Waker;
 use futures::Future;
 use heapless::Deque;
 
-use crate::blocking_mutex::kind::MutexKind;
+use crate::blocking_mutex::raw::RawMutex;
 use crate::blocking_mutex::Mutex;
 use crate::waitqueue::WakerRegistration;
 
@@ -56,7 +56,7 @@ use crate::waitqueue::WakerRegistration;
 /// Instances are created by the [`split`](split) function.
 pub struct Sender<'ch, M, T, const N: usize>
 where
-    M: MutexKind,
+    M: RawMutex,
 {
     channel: &'ch Channel<M, T, N>,
 }
@@ -66,7 +66,7 @@ where
 /// Instances are created by the [`split`](split) function.
 pub struct Receiver<'ch, M, T, const N: usize>
 where
-    M: MutexKind,
+    M: RawMutex,
 {
     channel: &'ch Channel<M, T, N>,
 }
@@ -99,7 +99,7 @@ pub fn split<M, T, const N: usize>(
     channel: &mut Channel<M, T, N>,
 ) -> (Sender<M, T, N>, Receiver<M, T, N>)
 where
-    M: MutexKind,
+    M: RawMutex,
 {
     let sender = Sender { channel };
     let receiver = Receiver { channel };
@@ -112,7 +112,7 @@ where
 
 impl<'ch, M, T, const N: usize> Receiver<'ch, M, T, N>
 where
-    M: MutexKind,
+    M: RawMutex,
 {
     /// Receives the next value for this receiver.
     ///
@@ -161,7 +161,7 @@ where
 
 impl<'ch, M, T, const N: usize> Drop for Receiver<'ch, M, T, N>
 where
-    M: MutexKind,
+    M: RawMutex,
 {
     fn drop(&mut self) {
         self.channel.lock(|c| c.deregister_receiver())
@@ -170,14 +170,14 @@ where
 
 pub struct RecvFuture<'ch, M, T, const N: usize>
 where
-    M: MutexKind,
+    M: RawMutex,
 {
     channel: &'ch Channel<M, T, N>,
 }
 
 impl<'ch, M, T, const N: usize> Future for RecvFuture<'ch, M, T, N>
 where
-    M: MutexKind,
+    M: RawMutex,
 {
     type Output = Option<T>;
 
@@ -193,7 +193,7 @@ where
 
 impl<'ch, M, T, const N: usize> Sender<'ch, M, T, N>
 where
-    M: MutexKind,
+    M: RawMutex,
 {
     /// Sends a value, waiting until there is capacity.
     ///
@@ -268,7 +268,7 @@ where
 
 pub struct SendFuture<'ch, M, T, const N: usize>
 where
-    M: MutexKind,
+    M: RawMutex,
 {
     channel: &'ch Channel<M, T, N>,
     message: Option<T>,
@@ -276,7 +276,7 @@ where
 
 impl<'ch, M, T, const N: usize> Future for SendFuture<'ch, M, T, N>
 where
-    M: MutexKind,
+    M: RawMutex,
 {
     type Output = Result<(), SendError<T>>;
 
@@ -295,18 +295,18 @@ where
     }
 }
 
-impl<'ch, M, T, const N: usize> Unpin for SendFuture<'ch, M, T, N> where M: MutexKind {}
+impl<'ch, M, T, const N: usize> Unpin for SendFuture<'ch, M, T, N> where M: RawMutex {}
 
 struct CloseFuture<'ch, M, T, const N: usize>
 where
-    M: MutexKind,
+    M: RawMutex,
 {
     channel: &'ch Channel<M, T, N>,
 }
 
 impl<'ch, M, T, const N: usize> Future for CloseFuture<'ch, M, T, N>
 where
-    M: MutexKind,
+    M: RawMutex,
 {
     type Output = ();
 
@@ -321,7 +321,7 @@ where
 
 impl<'ch, M, T, const N: usize> Drop for Sender<'ch, M, T, N>
 where
-    M: MutexKind,
+    M: RawMutex,
 {
     fn drop(&mut self) {
         self.channel.lock(|c| c.deregister_sender())
@@ -330,7 +330,7 @@ where
 
 impl<'ch, M, T, const N: usize> Clone for Sender<'ch, M, T, N>
 where
-    M: MutexKind,
+    M: RawMutex,
 {
     fn clone(&self) -> Self {
         self.channel.lock(|c| c.register_sender());
@@ -546,30 +546,50 @@ impl<T, const N: usize> 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: MutexKind,
+    M: RawMutex,
 {
-    inner: M::Mutex<RefCell<ChannelState<T, N>>>,
+    inner: Mutex<M, RefCell<ChannelState<T, N>>>,
 }
 
 impl<M, T, const N: usize> Channel<M, T, N>
 where
-    M: MutexKind,
+    M: RawMutex,
 {
     /// Establish a new bounded channel. For example, to create one with a NoopMutex:
     ///
     /// ```
     /// use embassy::channel::mpsc;
-    /// use embassy::blocking_mutex::kind::Noop;
+    /// use embassy::blocking_mutex::raw::NoopRawMutex;
     /// use embassy::channel::mpsc::Channel;
     ///
     /// // Declare a bounded channel of 3 u32s.
-    /// let mut channel = Channel::<Noop, u32, 3>::new();
+    /// let mut channel = Channel::<NoopRawMutex, u32, 3>::new();
     /// // once we have a channel, obtain its sender and receiver
     /// let (sender, receiver) = mpsc::split(&mut channel);
     /// ```
+    #[cfg(feature = "nightly")]
+    pub const fn new() -> Self {
+        Self {
+            inner: Mutex::new(RefCell::new(ChannelState::new())),
+        }
+    }
+
+    /// Establish a new bounded channel. For example, to create one with a NoopMutex:
+    ///
+    /// ```
+    /// use embassy::channel::mpsc;
+    /// use embassy::blocking_mutex::raw::NoopRawMutex;
+    /// use embassy::channel::mpsc::Channel;
+    ///
+    /// // Declare a bounded channel of 3 u32s.
+    /// let mut channel = Channel::<NoopRawMutex, u32, 3>::new();
+    /// // once we have a channel, obtain its sender and receiver
+    /// let (sender, receiver) = mpsc::split(&mut channel);
+    /// ```
+    #[cfg(not(feature = "nightly"))]
     pub fn new() -> Self {
         Self {
-            inner: M::Mutex::new(RefCell::new(ChannelState::new())),
+            inner: Mutex::new(RefCell::new(ChannelState::new())),
         }
     }
 
@@ -586,7 +606,7 @@ mod tests {
     use futures_executor::ThreadPool;
     use futures_timer::Delay;
 
-    use crate::blocking_mutex::kind::{CriticalSection, Noop};
+    use crate::blocking_mutex::raw::{CriticalSectionRawMutex, NoopRawMutex};
     use crate::util::Forever;
 
     use super::*;
@@ -655,7 +675,7 @@ mod tests {
 
     #[test]
     fn simple_send_and_receive() {
-        let mut c = Channel::<Noop, u32, 3>::new();
+        let mut c = Channel::<NoopRawMutex, u32, 3>::new();
         let (s, r) = split(&mut c);
         assert!(s.clone().try_send(1).is_ok());
         assert_eq!(r.try_recv().unwrap(), 1);
@@ -663,7 +683,7 @@ mod tests {
 
     #[test]
     fn should_close_without_sender() {
-        let mut c = Channel::<Noop, u32, 3>::new();
+        let mut c = Channel::<NoopRawMutex, u32, 3>::new();
         let (s, r) = split(&mut c);
         drop(s);
         match r.try_recv() {
@@ -674,7 +694,7 @@ mod tests {
 
     #[test]
     fn should_close_once_drained() {
-        let mut c = Channel::<Noop, u32, 3>::new();
+        let mut c = Channel::<NoopRawMutex, u32, 3>::new();
         let (s, r) = split(&mut c);
         assert!(s.try_send(1).is_ok());
         drop(s);
@@ -687,7 +707,7 @@ mod tests {
 
     #[test]
     fn should_reject_send_when_receiver_dropped() {
-        let mut c = Channel::<Noop, u32, 3>::new();
+        let mut c = Channel::<NoopRawMutex, u32, 3>::new();
         let (s, r) = split(&mut c);
         drop(r);
         match s.try_send(1) {
@@ -698,7 +718,7 @@ mod tests {
 
     #[test]
     fn should_reject_send_when_channel_closed() {
-        let mut c = Channel::<Noop, u32, 3>::new();
+        let mut c = Channel::<NoopRawMutex, u32, 3>::new();
         let (s, mut r) = split(&mut c);
         assert!(s.try_send(1).is_ok());
         r.close();
@@ -714,7 +734,7 @@ mod tests {
     async fn receiver_closes_when_sender_dropped_async() {
         let executor = ThreadPool::new().unwrap();
 
-        static CHANNEL: Forever<Channel<CriticalSection, u32, 3>> = Forever::new();
+        static CHANNEL: Forever<Channel<CriticalSectionRawMutex, u32, 3>> = Forever::new();
         let c = CHANNEL.put(Channel::new());
         let (s, mut r) = split(c);
         assert!(executor
@@ -729,7 +749,7 @@ mod tests {
     async fn receiver_receives_given_try_send_async() {
         let executor = ThreadPool::new().unwrap();
 
-        static CHANNEL: Forever<Channel<CriticalSection, u32, 3>> = Forever::new();
+        static CHANNEL: Forever<Channel<CriticalSectionRawMutex, u32, 3>> = Forever::new();
         let c = CHANNEL.put(Channel::new());
         let (s, mut r) = split(c);
         assert!(executor
@@ -742,7 +762,7 @@ mod tests {
 
     #[futures_test::test]
     async fn sender_send_completes_if_capacity() {
-        let mut c = Channel::<CriticalSection, u32, 1>::new();
+        let mut c = Channel::<CriticalSectionRawMutex, u32, 1>::new();
         let (s, mut r) = split(&mut c);
         assert!(s.send(1).await.is_ok());
         assert_eq!(r.recv().await, Some(1));
@@ -750,7 +770,7 @@ mod tests {
 
     #[futures_test::test]
     async fn sender_send_completes_if_closed() {
-        static CHANNEL: Forever<Channel<CriticalSection, u32, 1>> = Forever::new();
+        static CHANNEL: Forever<Channel<CriticalSectionRawMutex, u32, 1>> = Forever::new();
         let c = CHANNEL.put(Channel::new());
         let (s, r) = split(c);
         drop(r);
@@ -764,7 +784,7 @@ mod tests {
     async fn senders_sends_wait_until_capacity() {
         let executor = ThreadPool::new().unwrap();
 
-        static CHANNEL: Forever<Channel<CriticalSection, u32, 1>> = Forever::new();
+        static CHANNEL: Forever<Channel<CriticalSectionRawMutex, u32, 1>> = Forever::new();
         let c = CHANNEL.put(Channel::new());
         let (s0, mut r) = split(c);
         assert!(s0.try_send(1).is_ok());
@@ -784,7 +804,7 @@ mod tests {
 
     #[futures_test::test]
     async fn sender_close_completes_if_closing() {
-        static CHANNEL: Forever<Channel<CriticalSection, u32, 1>> = Forever::new();
+        static CHANNEL: Forever<Channel<CriticalSectionRawMutex, u32, 1>> = Forever::new();
         let c = CHANNEL.put(Channel::new());
         let (s, mut r) = split(c);
         r.close();
@@ -793,7 +813,7 @@ mod tests {
 
     #[futures_test::test]
     async fn sender_close_completes_if_closed() {
-        static CHANNEL: Forever<Channel<CriticalSection, u32, 1>> = Forever::new();
+        static CHANNEL: Forever<Channel<CriticalSectionRawMutex, u32, 1>> = Forever::new();
         let c = CHANNEL.put(Channel::new());
         let (s, r) = split(c);
         drop(r);

embassy/src/waitqueue/waker_agnostic.rs

@@ -2,7 +2,8 @@ use core::cell::Cell;
 use core::mem;
 use core::task::Waker;
 
-use crate::blocking_mutex::CriticalSectionMutex as Mutex;
+use crate::blocking_mutex::raw::CriticalSectionRawMutex;
+use crate::blocking_mutex::Mutex;
 
 /// Utility struct to register and wake a waker.
 #[derive(Debug)]
@@ -50,13 +51,13 @@ impl WakerRegistration {
 
 /// Utility struct to register and wake a waker.
 pub struct AtomicWaker {
-    waker: Mutex<Cell<Option<Waker>>>,
+    waker: Mutex<CriticalSectionRawMutex, Cell<Option<Waker>>>,
 }
 
 impl AtomicWaker {
     pub const fn new() -> Self {
         Self {
-            waker: Mutex::new(Cell::new(None)),
+            waker: Mutex::const_new(CriticalSectionRawMutex::new(), Cell::new(None)),
         }
     }
 

examples/nrf/src/bin/mpsc.rs

@@ -6,7 +6,7 @@
 mod example_common;
 
 use defmt::unwrap;
-use embassy::blocking_mutex::kind::Noop;
+use embassy::blocking_mutex::raw::NoopRawMutex;
 use embassy::channel::mpsc::{self, Channel, Sender, TryRecvError};
 use embassy::executor::Spawner;
 use embassy::time::{Duration, Timer};
@@ -19,10 +19,10 @@ enum LedState {
     Off,
 }
 
-static CHANNEL: Forever<Channel<Noop, LedState, 1>> = Forever::new();
+static CHANNEL: Forever<Channel<NoopRawMutex, LedState, 1>> = Forever::new();
 
 #[embassy::task(pool_size = 1)]
-async fn my_task(sender: Sender<'static, Noop, LedState, 1>) {
+async fn my_task(sender: Sender<'static, NoopRawMutex, LedState, 1>) {
     loop {
         let _ = sender.send(LedState::On).await;
         Timer::after(Duration::from_secs(1)).await;

examples/nrf/src/bin/uart_split.rs

@@ -6,7 +6,7 @@
 mod example_common;
 use example_common::*;
 
-use embassy::blocking_mutex::kind::Noop;
+use embassy::blocking_mutex::raw::NoopRawMutex;
 use embassy::channel::mpsc::{self, Channel, Sender};
 use embassy::executor::Spawner;
 use embassy::util::Forever;
@@ -15,7 +15,7 @@ use embassy_nrf::peripherals::UARTE0;
 use embassy_nrf::uarte::UarteRx;
 use embassy_nrf::{interrupt, uarte, Peripherals};
 
-static CHANNEL: Forever<Channel<Noop, [u8; 8], 1>> = Forever::new();
+static CHANNEL: Forever<Channel<NoopRawMutex, [u8; 8], 1>> = Forever::new();
 
 #[embassy::main]
 async fn main(spawner: Spawner, p: Peripherals) {
@@ -57,7 +57,7 @@ async fn main(spawner: Spawner, p: Peripherals) {
 }
 
 #[embassy::task]
-async fn reader(mut rx: UarteRx<'static, UARTE0>, s: Sender<'static, Noop, [u8; 8], 1>) {
+async fn reader(mut rx: UarteRx<'static, UARTE0>, s: Sender<'static, NoopRawMutex, [u8; 8], 1>) {
     let mut buf = [0; 8];
     loop {
         info!("reading...");

examples/stm32f3/src/bin/button_events.rs

@@ -12,7 +12,7 @@
 
 #[path = "../example_common.rs"]
 mod example_common;
-use embassy::blocking_mutex::kind::Noop;
+use embassy::blocking_mutex::raw::NoopRawMutex;
 use embassy::channel::mpsc::{self, Channel, Receiver, Sender};
 use embassy::executor::Spawner;
 use embassy::time::{with_timeout, Duration, Timer};
@@ -77,7 +77,7 @@ enum ButtonEvent {
     Hold,
 }
 
-static BUTTON_EVENTS_QUEUE: Forever<Channel<Noop, ButtonEvent, 4>> = Forever::new();
+static BUTTON_EVENTS_QUEUE: Forever<Channel<NoopRawMutex, ButtonEvent, 4>> = Forever::new();
 
 #[embassy::main]
 async fn main(spawner: Spawner, p: Peripherals) {
@@ -103,7 +103,10 @@ async fn main(spawner: Spawner, p: Peripherals) {
 }
 
 #[embassy::task]
-async fn led_blinker(mut leds: Leds<'static>, queue: Receiver<'static, Noop, ButtonEvent, 4>) {
+async fn led_blinker(
+    mut leds: Leds<'static>,
+    queue: Receiver<'static, NoopRawMutex, ButtonEvent, 4>,
+) {
     loop {
         leds.blink().await;
         match queue.try_recv() {
@@ -121,7 +124,7 @@ async fn led_blinker(mut leds: Leds<'static>, queue: Receiver<'static, Noop, But
 #[embassy::task]
 async fn button_waiter(
     mut button: ExtiInput<'static, PA0>,
-    queue: Sender<'static, Noop, ButtonEvent, 4>,
+    queue: Sender<'static, NoopRawMutex, ButtonEvent, 4>,
 ) {
     const DOUBLE_CLICK_DELAY: u64 = 250;
     const HOLD_DELAY: u64 = 1000;