Initialize class mutex and its spinlock correctly

include/mutex.hh

@@ -7,6 +7,8 @@
 
 class mutex {
 public:
+    mutex() { mutex_init(&_mutex); }
+    ~mutex() { mutex_destroy(&_mutex); }
     void lock();
     bool try_lock();
     void unlock();

include/osv/mutex.h

@@ -14,6 +14,11 @@ struct cspinlock {
 
 typedef struct cspinlock spinlock_t;
 
+static inline void spinlock_init(spinlock_t *sl)
+{
+    sl->lock = false;
+}
+
 struct cmutex {
     bool _locked;
     struct wait_list {
@@ -33,7 +38,10 @@ void mutex_unlock(mutex_t* m);
 
 static __always_inline void mutex_init(mutex_t* m)
 {
-    memset(m, 0, sizeof(*m));
+    m->_locked = false;
+    m->_wait_list.first = 0;
+    m->_wait_list.last = 0;
+    spinlock_init(&m->_wait_lock);
 }
 
 static __always_inline void mutex_destroy(mutex_t* m)