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, 27 insertions, 0 deletions

diff --git a/src/critical_section.rs b/src/critical_section.rs
new file mode 100644
index 0000000..688058d
--- /dev/null
+++ b/src/critical_section.rs
@@ -0,0 +1,27 @@
+#[cfg(all(cortex_m, feature = "critical-section-single-core"))]
+mod single_core_critical_section {
+    use critical_section::{set_impl, Impl, RawRestoreState};
+
+    use crate::interrupt;
+    use crate::register::primask;
+
+    struct SingleCoreCriticalSection;
+    set_impl!(SingleCoreCriticalSection);
+
+    unsafe impl Impl for SingleCoreCriticalSection {
+        unsafe fn acquire() -> RawRestoreState {
+            let was_active = primask::read().is_active();
+            interrupt::disable();
+            was_active
+        }
+
+        unsafe fn release(was_active: RawRestoreState) {
+            // Only re-enable interrupts if they were enabled before the critical section.
+            if was_active {
+                interrupt::enable()
+            }
+        }
+    }
+}
+
+pub use critical_section::with;