Use critical_section crate

embassy/Cargo.toml

@@ -25,6 +25,7 @@ pin-project = { version = "1.0.2", default-features = false }
 embassy-macros  = { version = "0.1.0", path = "../embassy-macros"}
 embassy-traits  = { version = "0.1.0", path = "../embassy-traits"}
 atomic-polyfill  = { version = "0.1.1" }
+critical-section = "0.2.0"
 
 # Workaround https://github.com/japaric/cast.rs/pull/27
 cast = { version = "=0.2.3", default-features = false }

embassy/src/util/critical_section.rs

@@ -1,30 +0,0 @@
-pub use cs::{critical_section, CriticalSection};
-
-#[cfg(feature = "std")]
-mod cs {
-    static INIT: std::sync::Once = std::sync::Once::new();
-    static mut BKL: Option<std::sync::Mutex<()>> = None;
-
-    pub type CriticalSection = std::sync::MutexGuard<'static, ()>;
-    pub fn critical_section<F, R>(f: F) -> R
-    where
-        F: FnOnce(&CriticalSection) -> R,
-    {
-        INIT.call_once(|| unsafe {
-            BKL.replace(std::sync::Mutex::new(()));
-        });
-        let guard = unsafe { BKL.as_ref().unwrap().lock().unwrap() };
-        f(&guard)
-    }
-}
-
-#[cfg(not(feature = "std"))]
-mod cs {
-    pub use cortex_m::interrupt::CriticalSection;
-    pub fn critical_section<F, R>(f: F) -> R
-    where
-        F: FnOnce(&CriticalSection) -> R,
-    {
-        cortex_m::interrupt::free(f)
-    }
-}

embassy/src/util/mod.rs

@@ -1,5 +1,4 @@
 //! Async utilities
-mod critical_section;
 mod drop_bomb;
 mod forever;
 mod mutex;
@@ -10,7 +9,6 @@ mod signal;
 #[cfg_attr(feature = "executor-agnostic", path = "waker_agnostic.rs")]
 mod waker;
 
-pub use critical_section::*;
 pub use drop_bomb::*;
 pub use forever::*;
 pub use mutex::*;

embassy/src/util/mutex.rs

@@ -1,5 +1,5 @@
 use core::cell::UnsafeCell;
-use cortex_m::interrupt::CriticalSection;
+use critical_section::CriticalSection;
 
 use crate::fmt::assert;
 
@@ -30,7 +30,7 @@ impl<T> CriticalSectionMutex<T> {
 
 impl<T> CriticalSectionMutex<T> {
     /// Borrows the data for the duration of the critical section
-    pub fn borrow<'cs>(&'cs self, _cs: &'cs CriticalSection) -> &'cs T {
+    pub fn borrow<'cs>(&'cs self, _cs: CriticalSection<'cs>) -> &'cs T {
         unsafe { &*self.inner.get() }
     }
 }

embassy/src/util/signal.rs

@@ -11,7 +11,6 @@ use ptr::NonNull;
 use crate::executor;
 use crate::fmt::panic;
 use crate::interrupt::{Interrupt, InterruptExt};
-use crate::util::critical_section::critical_section;
 
 /// Synchronization primitive. Allows creating awaitable signals that may be passed between tasks.
 ///
@@ -38,7 +37,7 @@ impl<T: Send> Signal<T> {
 
     /// Mark this Signal as completed.
     pub fn signal(&self, val: T) {
-        critical_section(|_| unsafe {
+        critical_section::with(|_| unsafe {
             let state = &mut *self.state.get();
             if let State::Waiting(waker) = mem::replace(state, State::Signaled(val)) {
                 waker.wake();
@@ -47,14 +46,14 @@ impl<T: Send> Signal<T> {
     }
 
     pub fn reset(&self) {
-        critical_section(|_| unsafe {
+        critical_section::with(|_| unsafe {
             let state = &mut *self.state.get();
             *state = State::None
         })
     }
 
     pub fn poll_wait(&self, cx: &mut Context<'_>) -> Poll<T> {
-        critical_section(|_| unsafe {
+        critical_section::with(|_| unsafe {
             let state = &mut *self.state.get();
             match state {
                 State::None => {
@@ -78,7 +77,7 @@ impl<T: Send> Signal<T> {
 
     /// non-blocking method to check whether this signal has been signaled.
     pub fn signaled(&self) -> bool {
-        critical_section(|_| matches!(unsafe { &*self.state.get() }, State::Signaled(_)))
+        critical_section::with(|_| matches!(unsafe { &*self.state.get() }, State::Signaled(_)))
     }
 }
 

embassy/src/util/waker_agnostic.rs

@@ -62,7 +62,7 @@ impl AtomicWaker {
 
     /// Register a waker. Overwrites the previous waker, if any.
     pub fn register(&mut self, w: &Waker) {
-        cortex_m::interrupt::free(|cs| {
+        critical_section::with(|cs| {
             let cell = self.waker.borrow(cs);
             cell.set(match cell.replace(None) {
                 Some(w2) if (w2.will_wake(w)) => Some(w2),
@@ -73,7 +73,7 @@ impl AtomicWaker {
 
     /// Wake the registered waker, if any.
     pub fn wake(&mut self) {
-        cortex_m::interrupt::free(|cs| {
+        critical_section::with(|cs| {
             let cell = self.waker.borrow(cs);
             if let Some(w) = cell.replace(None) {
                 w.wake_by_ref();