Add implementation for critical-section 1.0.

.github/workflows/ci.yml

@@ -29,6 +29,6 @@ jobs:
           toolchain: ${{ matrix.rust }}
           override: true
       - name: Run tests
-        run: cargo test --all
+        run: cargo test --all --features critical-section-single-core
 
 # FIXME: test on macOS and Windows

.github/workflows/clippy.yml

@@ -23,3 +23,4 @@ jobs:
       - uses: actions-rs/clippy-check@v1
         with:
           token: ${{ secrets.GITHUB_TOKEN }}
+          args: --features critical-section-single-core

CHANGELOG.md

@@ -7,6 +7,8 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 
 ## [Unreleased]
 
+- Added `critical-section-single-core` feature which provides an implementation for the `critical_section` crate for single-core systems, based on disabling all interrupts. (#448)
+
 ## [v0.7.5] - 2022-05-15
 
 ### Deprecated

Cargo.toml

@@ -17,6 +17,7 @@ links = "cortex-m"  # prevent multiple versions of this crate to be linked toget
 
 [dependencies]
 bare-metal = { version = "0.2.4", features = ["const-fn"] }
+critical-section = "1.0.0-alpha.2"
 volatile-register = "0.2.0"
 bitfield = "0.13.2"
 embedded-hal = "0.2.4"
@@ -32,6 +33,7 @@ cm7-r0p1 = ["cm7"]
 inline-asm = []
 linker-plugin-lto = []
 std = []
+critical-section-single-core = ["critical-section/restore-state-bool"]
 
 [workspace]
 members = ["xtask", "cortex-m-semihosting", "panic-semihosting", "panic-itm"]

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 active = primask::read().is_active();
+            if active {
+                interrupt::disable();
+            }
+            active
+        }
+
+        unsafe fn release(was_active: RawRestoreState) {
+            // Only re-enable interrupts if they were enabled before the critical section.
+            if was_active {
+                interrupt::enable()
+            }
+        }
+    }
+}

src/lib.rs

@@ -90,6 +90,7 @@ mod macros;
 pub mod asm;
 #[cfg(armv8m)]
 pub mod cmse;
+mod critical_section;
 pub mod delay;
 pub mod interrupt;
 #[cfg(all(not(armv6m), not(armv8m_base)))]

xtask/tests/ci.rs

@@ -32,6 +32,13 @@ fn build(package: &str, target: &str, features: &[&str]) {
         cargo.args(&["--features", *feat]);
     }
 
+    // A `critical_section` implementation is always needed.
+    if package == "cortex-m" {
+        cargo.args(&["--features", "critical-section-single-core"]);
+    } else {
+        cargo.args(&["--features", "cortex-m/critical-section-single-core"]);
+    }
+
     // Cargo features don't work right when invoked from the workspace root, so change to the
     // package's directory when necessary.
     if package != "cortex-m" {