core/mutex: support locked initialization

core/include/mutex.h

@@ -49,6 +49,18 @@ typedef struct {
  */
 #define MUTEX_INIT { { NULL } }
 
+/**
+ * @brief Static initializer for mutex_t with a locked mutex
+ */
+#define MUTEX_INIT_LOCKED { { MUTEX_LOCKED } }
+
+/**
+ * @internal
+ * @brief This is the value of the mutex when locked and no threads are waiting
+ *        for it
+ */
+#define MUTEX_LOCKED ((void *)-1)
+
 /**
  * @brief Initializes a mutex object.
  * @details For initialization of variables use MUTEX_INIT instead.

core/mutex.c

@@ -35,8 +35,6 @@
 #define ENABLE_DEBUG    (0)
 #include "debug.h"
 
-#define MUTEX_LOCKED ((void*)-1)
-
 int _mutex_lock(mutex_t *mutex, int blocking)
 {
     unsigned irqstate = irq_disable();