Added arch specific mutex implementation

Cargo.toml

@@ -18,6 +18,7 @@ links = "cortex-m"  # prevent multiple versions of this crate to be linked toget
 [dependencies]
 bare-metal = { version = "0.2.0", features = ["const-fn"] }
 volatile-register = "0.2.0"
+mutex-trait = "0.2.0"
 bitfield = "0.13.2"
 
 [features]

src/lib.rs

@@ -66,5 +66,6 @@ pub mod interrupt;
 pub mod itm;
 pub mod peripheral;
 pub mod register;
+pub mod mutex;
 
 pub use crate::peripheral::Peripherals;

src/mutex.rs

@@ -0,0 +1,34 @@
+//! Implementation of a critical section based mutex that also implements the `mutex-trait`.
+//!
+//! ## Safety
+//!
+//! Note that this is only safe in single core applications.
+
+use core::cell::UnsafeCell;
+
+/// A critical section based mutex.
+pub struct CriticalSectionMutex<T> {
+    data: UnsafeCell<T>,
+}
+
+impl<T> CriticalSectionMutex<T> {
+    /// Create a new mutex
+    pub const fn new(data: T) -> Self {
+        CriticalSectionMutex {
+            data: UnsafeCell::new(data),
+        }
+    }
+}
+
+impl<T> mutex_trait::Mutex for &'_ CriticalSectionMutex<T> {
+    type Data = T;
+
+    fn lock<R>(&mut self, f: impl FnOnce(&mut Self::Data) -> R) -> R {
+        crate::interrupt::free(|_| f(unsafe { &mut *self.data.get() }))
+    }
+}
+
+// NOTE A `Mutex` can be used as a channel so the protected data must be `Send`
+// to prevent sending non-Sendable stuff (e.g. access tokens) across different
+// execution contexts (e.g. interrupts)
+unsafe impl<T> Sync for CriticalSectionMutex<T> where T: Send {}