From 527bfb6eecf626b34996511689b80654ba0e26ed Mon Sep 17 00:00:00 2001
From: Per Lindgren <per.lindgren@ltu.se>
Date: Sat, 13 Jun 2020 21:07:55 +0200
Subject: [PATCH] added compiler_fence(Ordering::SeqCst) around critical
 sections

---
 src/export.rs | 18 +++++++++++++++---
 1 file changed, 15 insertions(+), 3 deletions(-)

diff --git a/src/export.rs b/src/export.rs
index e23b8f3a8b..4794f6988a 100644
--- a/src/export.rs
+++ b/src/export.rs
@@ -1,6 +1,6 @@
 use core::{
     cell::Cell,
-    sync::atomic::{AtomicBool, Ordering},
+    sync::atomic::{compiler_fence, AtomicBool, Ordering},
 };
 
 pub use crate::tq::{NotReady, TimerQueue};
@@ -129,13 +129,20 @@ pub unsafe fn lock<T, R>(
     if current < ceiling {
         if ceiling == (1 << nvic_prio_bits) {
             priority.set(u8::max_value());
-            let r = interrupt::free(|_| f(&mut *ptr));
+            let r = interrupt::free(|_| {
+                compiler_fence(Ordering::SeqCst);
+                let r = f(&mut *ptr);
+                compiler_fence(Ordering::SeqCst);
+                r
+            });
             priority.set(current);
             r
         } else {
             priority.set(ceiling);
             basepri::write(logical2hw(ceiling, nvic_prio_bits));
+            compiler_fence(Ordering::SeqCst);
             let r = f(&mut *ptr);
+            compiler_fence(Ordering::SeqCst);
             basepri::write(logical2hw(current, nvic_prio_bits));
             priority.set(current);
             r
@@ -158,7 +165,12 @@ pub unsafe fn lock<T, R>(
 
     if current < ceiling {
         priority.set(u8::max_value());
-        let r = interrupt::free(|_| f(&mut *ptr));
+        let r = interrupt::free(|_| {
+            compiler_fence(Ordering::SeqCst);
+            let r = f(&mut *ptr);
+            compiler_fence(Ordering::SeqCst);
+            r
+        });
         priority.set(current);
         r
     } else {