mutex: Add TryLock() variants.

nx/include/switch/kernel/mutex.h

@@ -29,6 +29,13 @@ static inline void mutexInit(Mutex* m)
  */
 void mutexLock(Mutex* m);
 
+/**
+ * @brief Attempts to lock a mutex without waiting.
+ * @param m Mutex object.
+ * @return 1 if the mutex has been acquired successfully, and 0 on contention.
+ */
+u32 mutexTryLock(Mutex* m);
+
 /**
  * @brief Unlocks a mutex.
  * @param m Mutex object.
@@ -53,6 +60,13 @@ static inline void rmutexInit(RMutex* m)
  */
 void rmutexLock(RMutex* m);
 
+/**
+ * @brief Attempts to lock a recursive mutex without waiting.
+ * @param m Recursive mutex object.
+ * @return 1 if the mutex has been acquired successfully, and 0 on contention.
+ */
+u32 rmutexTryLock(RMutex* m);
+
 /**
  * @brief Unlocks a recursive mutex.
  * @param m Recursive mutex object.

nx/source/kernel/mutex.c

@@ -41,6 +41,23 @@ void mutexLock(Mutex* m) {
     }
 }
 
+u32 mutexTryLock(Mutex* m) {
+    u32 self = _GetTag();
+    u32 cur = __sync_val_compare_and_swap((u32*)m, 0, self);
+
+    if (cur == 0) {
+        // We won the race!
+        return 1;
+    }
+
+    if ((cur &~ HAS_LISTENERS) == self) {
+        // Kernel assigned it to us!
+        return 1;
+    }
+    
+    return 0;
+}
+
 void mutexUnlock(Mutex* m) {
     u32 old = __sync_lock_test_and_set((u32*)m, 0);
 
@@ -58,6 +75,18 @@ void rmutexLock(RMutex* m) {
     m->counter++;
 }
 
+u32 rmutexTryLock(RMutex* m) {
+    if (m->thread_tag != _GetTag()) {
+        if (!mutexTryLock(&m->lock)) {
+            return 0;
+        }
+        m->thread_tag = _GetTag();
+    }
+
+    m->counter++;
+    return 1;
+}
+
 void rmutexUnlock(RMutex* m) {
     if (--m->counter == 0) {
         m->thread_tag = 0;