From 074438c3c7becd30a08a59490754f3120a0650f0 Mon Sep 17 00:00:00 2001
From: pca006132 <john.lck40@gmail.com>
Date: Wed, 15 Jul 2020 16:41:28 +0800
Subject: [PATCH] libcortex_a9: added `try_lock` for mutex.

---
 libcortex_a9/src/mutex.rs | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/libcortex_a9/src/mutex.rs b/libcortex_a9/src/mutex.rs
index 9d3c6c6..8d84105 100644
--- a/libcortex_a9/src/mutex.rs
+++ b/libcortex_a9/src/mutex.rs
@@ -48,6 +48,15 @@ impl<T> Mutex<T> {
         MutexGuard { mutex: self }
     }
 
+    pub fn try_lock(&self) -> Option<MutexGuard<T>> {
+        if self.locked.compare_and_swap(UNLOCKED, LOCKED, Ordering::Acquire) != UNLOCKED {
+            None
+        } else {
+            dmb();
+            Some(MutexGuard { mutex: self })
+        }
+    }
+
     fn unlock(&self) {
         dmb();
         self.locked.store(UNLOCKED, Ordering::Release);