mutex-cortex: add comment on definition of mutex_try_lock
as a response to
#include <stdbool.h>
#include "atomic-cortex.h"
/*---------------------------------------------------------------------------*/
+/*
+ * mutex_t for cortex is uint8_t (see below). That's why we can just
+ * use atomic_cortex_cas_uint8 for mutex_try_lock. Note that mutex_t
+ * may NOT be uint8_t in other platforms.
+ */
#define mutex_try_lock(m) atomic_cortex_cas_uint8((m),0,1)
#define mutex_unlock(m) mutex_cortex_unlock(m)
/*---------------------------------------------------------------------------*/
