UnsafeCell test

1 files changed, 9 insertions, 4 deletions

diff --git a/src/mutex.rs b/src/mutex.rs
index 7346e35..6948512 100644
--- a/src/mutex.rs
+++ b/src/mutex.rs
@@ -1,17 +1,17 @@
 //! Implementation of a critical section based mutex that also implements the `mutex-trait`.
 
-use core::cell::RefCell;
+use core::cell::UnsafeCell;
 
 /// A critical section based mutex
 pub struct CriticalSectionMutex<T> {
-    data: RefCell<T>,
+    data: UnsafeCell<T>,
 }
 
 impl<T> CriticalSectionMutex<T> {
     /// Create a new mutex
     pub const fn new(data: T) -> Self {
         CriticalSectionMutex {
-            data: RefCell::new(data),
+            data: UnsafeCell::new(data),
         }
     }
 }
@@ -20,6 +20,11 @@ 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(&mut *self.data.borrow_mut()))
+        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 {}