Merge #447

447: Add implementation for critical-section 1.0 r=adamgreig a=Dirbaio

Picking up #433 since it seems stalled. Changes from #433 are:
- Update to `critical-section 1.0.0-alpha.2`
- Use `bool` restore token
- Name Cargo feature `critical-section-single-core`.

TODO before merging:

- [x] Wait for `critical-section 1.0` release https://github.com/rust-embedded/critical-section/pull/19

Co-Authored-By: Markus Reiter `@reitermarkus` 

Co-authored-by: Dario Nieuwenhuis <dirbaio@dirbaio.net>

1 files changed, 13 insertions, 9 deletions

diff --git a/src/interrupt.rs b/src/interrupt.rs
index 72450c4..f6ce990 100644
--- a/src/interrupt.rs
+++ b/src/interrupt.rs
@@ -1,6 +1,5 @@
 //! Interrupts
 
-pub use bare_metal::{CriticalSection, Mutex};
 #[cfg(cortex_m)]
 use core::arch::asm;
 #[cfg(cortex_m)]
@@ -27,7 +26,7 @@ pub unsafe trait InterruptNumber: Copy {
     fn number(self) -> u16;
 }
 
-/// Disables all interrupts
+/// Disables all interrupts in the current core.
 #[cfg(cortex_m)]
 #[inline]
 pub fn disable() {
@@ -39,11 +38,11 @@ pub fn disable() {
     compiler_fence(Ordering::SeqCst);
 }
 
-/// Enables all the interrupts
+/// Enables all the interrupts in the current core.
 ///
 /// # Safety
 ///
-/// - Do not call this function inside an `interrupt::free` critical section
+/// - Do not call this function inside a critical section.
 #[cfg(cortex_m)]
 #[inline]
 pub unsafe fn enable() {
@@ -53,21 +52,26 @@ pub unsafe fn enable() {
     asm!("cpsie i", options(nomem, nostack, preserves_flags));
 }
 
-/// Execute closure `f` in an interrupt-free context.
+/// Execute closure `f` with interrupts disabled in the current core.
 ///
-/// This as also known as a "critical section".
+/// This method does not synchronise multiple cores and may disable required
+/// interrupts on some platforms; see the `critical-section` crate for a cross-platform
+/// way to enter a critical section which provides a `CriticalSection` token.
+///
+/// This crate provides an implementation for `critical-section` suitable for single-core systems,
+/// based on disabling all interrupts. It can be enabled with the `critical-section-single-core` feature.
 #[cfg(cortex_m)]
 #[inline]
 pub fn free<F, R>(f: F) -> R
 where
-    F: FnOnce(&CriticalSection) -> R,
+    F: FnOnce() -> R,
 {
     let primask = crate::register::primask::read();
 
     // disable interrupts
     disable();
 
-    let r = f(unsafe { &CriticalSection::new() });
+    let r = f();
 
     // If the interrupts were active before our `disable` call, then re-enable
     // them. Otherwise, keep them disabled
@@ -85,7 +89,7 @@ where
 #[inline]
 pub fn free<F, R>(_: F) -> R
 where
-    F: FnOnce(&CriticalSection) -> R,
+    F: FnOnce() -> R,
 {
     panic!("cortex_m::interrupt::free() is only functional on cortex-m platforms");
 }