add Mutex.borrow_mut method

Author: Jorge Aparicio

src/interrupt.rs

@@ -19,6 +19,11 @@ impl<T> Mutex<T> {
     pub fn borrow<'cs>(&self, _ctxt: &'cs CriticalSection) -> &'cs T {
         unsafe { &*self.inner.get() }
     }
+
+    /// Mutably borrows the data for the duration of the critical section
+    pub fn borrow_mut<'cs>(&self, _ctxt: &'cs mut CriticalSection) -> &'cs mut T {
+        unsafe { &mut *self.inner.get() }
+    }
 }
 
 /// Interrupt number
@@ -75,14 +80,14 @@ pub struct CriticalSection {
 /// This as also known as a "critical section".
 pub fn free<F, R>(f: F) -> R
 where
-    F: FnOnce(&CriticalSection) -> R,
+    F: FnOnce(CriticalSection) -> R,
 {
     let primask = ::register::primask::read();
 
     // disable interrupts
     disable();
 
-    let r = f(&CriticalSection { _0: () });
+    let r = f(CriticalSection { _0: () });
 
     // If the interrupts were active before our `disable` call, then re-enable
     // them. Otherwise, keep them disabled