17 files changed, 41 insertions, 157 deletions

diff --git a/embassy-extras/src/macros.rs b/embassy-extras/src/macros.rs
index d85439358..860c0795a 100644
--- a/embassy-extras/src/macros.rs
+++ b/embassy-extras/src/macros.rs
@@ -51,7 +51,7 @@ macro_rules! peripherals {
                 #[no_mangle]
                 static mut _EMBASSY_DEVICE_PERIPHERALS: bool = false;
 
-                cortex_m::interrupt::free(|_| {
+                critical_section::with(|_| {
                     if unsafe { _EMBASSY_DEVICE_PERIPHERALS } {
                         None
                     } else {
diff --git a/embassy-nrf/Cargo.toml b/embassy-nrf/Cargo.toml
index 8ec5b0878..b8b63bbb1 100644
--- a/embassy-nrf/Cargo.toml
+++ b/embassy-nrf/Cargo.toml
@@ -36,3 +36,4 @@ nrf52811-pac  = { version = "0.9.1", optional = true, features = [ "rt" ]}
 nrf52832-pac  = { version = "0.9.0", optional = true, features = [ "rt" ]}
 nrf52833-pac  = { version = "0.9.0", optional = true, features = [ "rt" ]}
 nrf52840-pac  = { version = "0.9.0", optional = true, features = [ "rt" ]}
+critical-section = "0.2.0"
diff --git a/embassy-nrf/src/interrupt.rs b/embassy-nrf/src/interrupt.rs
index 741dbaee2..8d069e329 100644
--- a/embassy-nrf/src/interrupt.rs
+++ b/embassy-nrf/src/interrupt.rs
@@ -8,7 +8,6 @@ use core::sync::atomic::{compiler_fence, Ordering};
 use crate::pac::NVIC_PRIO_BITS;
 
 // Re-exports
-pub use cortex_m::interrupt::{CriticalSection, Mutex};
 pub use embassy::interrupt::{declare, take, Interrupt};
 
 #[derive(Debug, Copy, Clone, Eq, PartialEq, Ord, PartialOrd)]
@@ -47,35 +46,6 @@ impl From<Priority> for u8 {
     }
 }
 
-#[inline]
-pub fn free<F, R>(f: F) -> R
-where
-    F: FnOnce(&CriticalSection) -> R,
-{
-    unsafe {
-        // TODO: assert that we're in privileged level
-        // Needed because disabling irqs in non-privileged level is a noop, which would break safety.
-
-        let primask: u32;
-        asm!("mrs {}, PRIMASK", out(reg) primask);
-
-        asm!("cpsid i");
-
-        // Prevent compiler from reordering operations inside/outside the critical section.
-        compiler_fence(Ordering::SeqCst);
-
-        let r = f(&CriticalSection::new());
-
-        compiler_fence(Ordering::SeqCst);
-
-        if primask & 1 == 0 {
-            asm!("cpsie i");
-        }
-
-        r
-    }
-}
-
 #[cfg(feature = "52810")]
 mod irqs {
     use super::*;
diff --git a/embassy-nrf/src/rtc.rs b/embassy-nrf/src/rtc.rs
index cbb5a87ef..dc0e3ceb6 100644
--- a/embassy-nrf/src/rtc.rs
+++ b/embassy-nrf/src/rtc.rs
@@ -1,10 +1,11 @@
 use core::cell::Cell;
 use core::sync::atomic::{compiler_fence, AtomicU32, Ordering};
-
+use critical_section::CriticalSection;
 use embassy::interrupt::InterruptExt;
 use embassy::time::Clock;
+use embassy::util::CriticalSectionMutex as Mutex;
 
-use crate::interrupt::{CriticalSection, Interrupt, Mutex};
+use crate::interrupt::Interrupt;
 use crate::pac;
 use crate::{interrupt, peripherals};
 
@@ -134,7 +135,7 @@ impl<T: Instance> RTC<T> {
         for n in 0..ALARM_COUNT {
             if r.events_compare[n].read().bits() == 1 {
                 r.events_compare[n].write(|w| w);
-                interrupt::free(|cs| {
+                critical_section::with(|cs| {
                     self.trigger_alarm(n, cs);
                 })
             }
@@ -142,7 +143,7 @@ impl<T: Instance> RTC<T> {
     }
 
     fn next_period(&self) {
-        interrupt::free(|cs| {
+        critical_section::with(|cs| {
             let r = self.rtc.regs();
             let period = self.period.fetch_add(1, Ordering::Relaxed) + 1;
             let t = (period as u64) << 23;
@@ -160,7 +161,7 @@ impl<T: Instance> RTC<T> {
         })
     }
 
-    fn trigger_alarm(&self, n: usize, cs: &CriticalSection) {
+    fn trigger_alarm(&self, n: usize, cs: CriticalSection) {
         let r = self.rtc.regs();
         r.intenclr.write(|w| unsafe { w.bits(compare_n(n)) });
 
@@ -174,14 +175,14 @@ impl<T: Instance> RTC<T> {
     }
 
     fn set_alarm_callback(&self, n: usize, callback: fn(*mut ()), ctx: *mut ()) {
-        interrupt::free(|cs| {
+        critical_section::with(|cs| {
             let alarm = &self.alarms.borrow(cs)[n];
             alarm.callback.set(Some((callback, ctx)));
         })
     }
 
     fn set_alarm(&self, n: usize, timestamp: u64) {
-        interrupt::free(|cs| {
+        critical_section::with(|cs| {
             let alarm = &self.alarms.borrow(cs)[n];
             alarm.timestamp.set(timestamp);
 
@@ -289,5 +290,5 @@ pub trait Instance: sealed::Instance + 'static {
 
 impl_instance!(RTC0, RTC0);
 impl_instance!(RTC1, RTC1);
-#[cfg(any(feature = "52832", feature = "52833", feature = "52840"))]
+#[cfg(any(feature = "nrf52832", feature = "nrf52833", feature = "nrf52840"))]
 impl_instance!(RTC2, RTC2);
diff --git a/embassy-rp/Cargo.toml b/embassy-rp/Cargo.toml
index 1d11fb0d7..59331dd1d 100644
--- a/embassy-rp/Cargo.toml
+++ b/embassy-rp/Cargo.toml
@@ -20,6 +20,7 @@ defmt = { version = "0.2.0", optional = true }
 log = { version = "0.4.11", optional = true }
 cortex-m-rt = "0.6.13"
 cortex-m = "0.7.1"
+critical-section = "0.2.0"
 
 rp2040-pac2 = { git = "https://github.com/Dirbaio/rp2040-pac", rev="254f4677937801155ca3cb17c7bb9d38eb62683e", features = ["rt"] }
 embedded-hal = { version = "0.2.4", features = [ "unproven" ] }
diff --git a/embassy-rp/src/interrupt.rs b/embassy-rp/src/interrupt.rs
index a913ea60c..cb9f36546 100644
--- a/embassy-rp/src/interrupt.rs
+++ b/embassy-rp/src/interrupt.rs
@@ -8,7 +8,6 @@ use core::sync::atomic::{compiler_fence, Ordering};
 use crate::pac::NVIC_PRIO_BITS;
 
 // Re-exports
-pub use cortex_m::interrupt::{CriticalSection, Mutex};
 pub use embassy::interrupt::{declare, take, Interrupt};
 
 #[derive(Debug, Copy, Clone, Eq, PartialEq, Ord, PartialOrd)]
@@ -47,35 +46,6 @@ impl From<Priority> for u8 {
     }
 }
 
-#[inline]
-pub fn free<F, R>(f: F) -> R
-where
-    F: FnOnce(&CriticalSection) -> R,
-{
-    unsafe {
-        // TODO: assert that we're in privileged level
-        // Needed because disabling irqs in non-privileged level is a noop, which would break safety.
-
-        let primask: u32;
-        asm!("mrs {}, PRIMASK", out(reg) primask);
-
-        asm!("cpsid i");
-
-        // Prevent compiler from reordering operations inside/outside the critical section.
-        compiler_fence(Ordering::SeqCst);
-
-        let r = f(&CriticalSection::new());
-
-        compiler_fence(Ordering::SeqCst);
-
-        if primask & 1 == 0 {
-            asm!("cpsie i");
-        }
-
-        r
-    }
-}
-
 mod irqs {
     use super::*;
 
diff --git a/embassy-stm32/Cargo.toml b/embassy-stm32/Cargo.toml
index af30f1aae..36bc0f25e 100644
--- a/embassy-stm32/Cargo.toml
+++ b/embassy-stm32/Cargo.toml
@@ -39,6 +39,7 @@ embassy-macros = { version = "0.1.0", path = "../embassy-macros", features = ["s
 embassy-extras = {version = "0.1.0", path = "../embassy-extras" }
 
 atomic-polyfill = "0.1.1"
+critical-section = "0.2.0"
 defmt = { version = "0.2.0", optional = true }
 log = { version = "0.4.11", optional = true }
 cortex-m-rt = "0.6.13"
diff --git a/embassy-stm32/src/exti.rs b/embassy-stm32/src/exti.rs
index 9a12f8115..3d83c2d53 100644
--- a/embassy-stm32/src/exti.rs
+++ b/embassy-stm32/src/exti.rs
@@ -44,7 +44,7 @@ pub struct ExtiPin<T: Instance> {
 
 impl<T: Instance> ExtiPin<T> {
     pub fn new(mut pin: T, interrupt: T::Interrupt, syscfg: &mut SysCfg) -> Self {
-        cortex_m::interrupt::free(|_| {
+        critical_section::with(|_| {
             pin.make_source(syscfg);
         });
 
@@ -99,7 +99,7 @@ impl<T: Instance + digital::InputPin + 'static> ExtiPin<T> {
         async move {
             let fut = InterruptFuture::new(&mut self.interrupt);
             let pin = &mut self.pin;
-            cortex_m::interrupt::free(|_| {
+            critical_section::with(|_| {
                 pin.trigger_edge(if state {
                     EdgeOption::Rising
                 } else {
@@ -126,7 +126,7 @@ impl<T: Instance + 'static> ExtiPin<T> {
         async move {
             let fut = InterruptFuture::new(&mut self.interrupt);
             let pin = &mut self.pin;
-            cortex_m::interrupt::free(|_| {
+            critical_section::with(|_| {
                 pin.trigger_edge(state);
             });
 
diff --git a/embassy-stm32/src/f4/rtc.rs b/embassy-stm32/src/f4/rtc.rs
index b1abba325..df7a82d87 100644
--- a/embassy-stm32/src/f4/rtc.rs
+++ b/embassy-stm32/src/f4/rtc.rs
@@ -3,12 +3,13 @@ use crate::hal::rcc::Clocks;
 use core::cell::Cell;
 use core::convert::TryInto;
 use core::sync::atomic::{compiler_fence, AtomicU32, Ordering};
-
+use critical_section::CriticalSection;
 use embassy::interrupt::InterruptExt;
 use embassy::time::{Clock, TICKS_PER_SECOND};
+use embassy::util::CriticalSectionMutex as Mutex;
 
 use crate::interrupt;
-use crate::interrupt::{CriticalSection, Interrupt, Mutex};
+use crate::interrupt::Interrupt;
 
 // RTC timekeeping works with something we call "periods", which are time intervals
 // of 2^15 ticks. The RTC counter value is 16 bits, so one "overflow cycle" is 2 periods.
@@ -119,13 +120,13 @@ impl<T: Instance> RTC<T> {
         for n in 1..=ALARM_COUNT {
             if self.rtc.compare_interrupt_status(n) {
                 self.rtc.compare_clear_flag(n);
-                interrupt::free(|cs| self.trigger_alarm(n, cs));
+                critical_section::with(|cs| self.trigger_alarm(n, cs));
             }
         }
     }
 
     fn next_period(&self) {
-        interrupt::free(|cs| {
+        critical_section::with(|cs| {
             let period = self.period.fetch_add(1, Ordering::Relaxed) + 1;
             let t = (period as u64) << 15;
 
@@ -142,7 +143,7 @@ impl<T: Instance> RTC<T> {
         })
     }
 
-    fn trigger_alarm(&self, n: usize, cs: &CriticalSection) {
+    fn trigger_alarm(&self, n: usize, cs: CriticalSection) {
         self.rtc.set_compare_interrupt(n, false);
 
         let alarm = &self.alarms.borrow(cs)[n - 1];
@@ -155,14 +156,14 @@ impl<T: Instance> RTC<T> {
     }
 
     fn set_alarm_callback(&self, n: usize, callback: fn(*mut ()), ctx: *mut ()) {
-        interrupt::free(|cs| {
+        critical_section::with(|cs| {
             let alarm = &self.alarms.borrow(cs)[n - 1];
             alarm.callback.set(Some((callback, ctx)));
         })
     }
 
     fn set_alarm(&self, n: usize, timestamp: u64) {
-        interrupt::free(|cs| {
+        critical_section::with(|cs| {
             let alarm = &self.alarms.borrow(cs)[n - 1];
             alarm.timestamp.set(timestamp);
 
diff --git a/embassy-stm32/src/interrupt.rs b/embassy-stm32/src/interrupt.rs
index 63b80a6c9..1d48dc584 100644
--- a/embassy-stm32/src/interrupt.rs
+++ b/embassy-stm32/src/interrupt.rs
@@ -8,7 +8,6 @@ use core::sync::atomic::{compiler_fence, Ordering};
 use crate::pac::NVIC_PRIO_BITS;
 
 // Re-exports
-pub use cortex_m::interrupt::{CriticalSection, Mutex};
 pub use embassy::interrupt::{declare, take, Interrupt};
 
 #[derive(Debug, Copy, Clone, Eq, PartialEq, Ord, PartialOrd)]
@@ -63,35 +62,6 @@ impl From<Priority> for u8 {
     }
 }
 
-#[inline]
-pub fn free<F, R>(f: F) -> R
-where
-    F: FnOnce(&CriticalSection) -> R,
-{
-    unsafe {
-        // TODO: assert that we're in privileged level
-        // Needed because disabling irqs in non-privileged level is a noop, which would break safety.
-
-        let primask: u32;
-        asm!("mrs {}, PRIMASK", out(reg) primask);
-
-        asm!("cpsid i");
-
-        // Prevent compiler from reordering operations inside/outside the critical section.
-        compiler_fence(Ordering::SeqCst);
-
-        let r = f(&CriticalSection::new());
-
-        compiler_fence(Ordering::SeqCst);
-
-        if primask & 1 == 0 {
-            asm!("cpsie i");
-        }
-
-        r
-    }
-}
-
 #[cfg(feature = "stm32f401")]
 mod irqs {
     use super::*;
diff --git a/embassy-stm32/src/l0/rtc.rs b/embassy-stm32/src/l0/rtc.rs
index 9a1342044..fa5011d3a 100644
--- a/embassy-stm32/src/l0/rtc.rs
+++ b/embassy-stm32/src/l0/rtc.rs
@@ -2,12 +2,13 @@ use crate::hal::rcc::Clocks;
 use atomic_polyfill::{compiler_fence, AtomicU32, Ordering};
 use core::cell::Cell;
 use core::convert::TryInto;
-
+use critical_section::CriticalSection;
 use embassy::interrupt::InterruptExt;
 use embassy::time::{Clock, TICKS_PER_SECOND};
+use embassy::util::CriticalSectionMutex as Mutex;
 
 use crate::interrupt;
-use crate::interrupt::{CriticalSection, Interrupt, Mutex};
+use crate::interrupt::Interrupt;
 
 // RTC timekeeping works with something we call "periods", which are time intervals
 // of 2^15 ticks. The RTC counter value is 16 bits, so one "overflow cycle" is 2 periods.
@@ -117,13 +118,13 @@ impl<T: Instance> RTC<T> {
         for n in 1..=ALARM_COUNT {
             if self.rtc.compare_interrupt_status(n) {
                 self.rtc.compare_clear_flag(n);
-                interrupt::free(|cs| self.trigger_alarm(n, cs));
+                critical_section::with(|cs| self.trigger_alarm(n, cs));
             }
         }
     }
 
     fn next_period(&self) {
-        interrupt::free(|cs| {
+        critical_section::with(|cs| {
             let period = self.period.fetch_add(1, Ordering::Relaxed) + 1;
             let t = (period as u64) << 15;
 
@@ -140,7 +141,7 @@ impl<T: Instance> RTC<T> {
         })
     }
 
-    fn trigger_alarm(&self, n: usize, cs: &CriticalSection) {
+    fn trigger_alarm(&self, n: usize, cs: CriticalSection) {
         self.rtc.set_compare_interrupt(n, false);
 
         let alarm = &self.alarms.borrow(cs)[n - 1];
@@ -153,14 +154,14 @@ impl<T: Instance> RTC<T> {
     }
 
     fn set_alarm_callback(&self, n: usize, callback: fn(*mut ()), ctx: *mut ()) {
-        interrupt::free(|cs| {
+        critical_section::with(|cs| {
             let alarm = &self.alarms.borrow(cs)[n - 1];
             alarm.callback.set(Some((callback, ctx)));
         })
     }
 
     fn set_alarm(&self, n: usize, timestamp: u64) {
-        interrupt::free(|cs| {
+        critical_section::with(|cs| {
             let alarm = &self.alarms.borrow(cs)[n - 1];
             alarm.timestamp.set(timestamp);
 
diff --git a/embassy/Cargo.toml b/embassy/Cargo.toml
index 2f3ee453c..2395eeae7 100644
--- a/embassy/Cargo.toml
+++ b/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 }
diff --git a/embassy/src/util/critical_section.rs b/embassy/src/util/critical_section.rs
deleted file mode 100644
index 12ad6f20e..000000000
--- a/embassy/src/util/critical_section.rs
+++ /dev/null
@@ -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)
-    }
-}
diff --git a/embassy/src/util/mod.rs b/embassy/src/util/mod.rs
index cace0d190..6aa3a7330 100644
--- a/embassy/src/util/mod.rs
+++ b/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::*;
diff --git a/embassy/src/util/mutex.rs b/embassy/src/util/mutex.rs
index ed2fd7852..86ab070a3 100644
--- a/embassy/src/util/mutex.rs
+++ b/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() }
     }
 }
diff --git a/embassy/src/util/signal.rs b/embassy/src/util/signal.rs
index a62abcd55..2eefe658b 100644
--- a/embassy/src/util/signal.rs
+++ b/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(_)))
     }
 }
 
diff --git a/embassy/src/util/waker_agnostic.rs b/embassy/src/util/waker_agnostic.rs
index 3f6ad373a..53f1ec135 100644
--- a/embassy/src/util/waker_agnostic.rs
+++ b/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();