use atomics in critnib find_*

Author: bratpiorka

src/critnib/critnib.c

@@ -523,7 +523,9 @@ find_predecessor(struct critnib_node *__restrict n) {
     while (1) {
         int nib;
         for (nib = NIB; nib >= 0; nib--) {
-            if (n->child[nib]) {
+            struct critnib_node *m;
+            utils_atomic_load_acquire_ptr((void **)&n->child[nib], (void **)&m);
+            if (m) {
                 break;
             }
         }
@@ -532,7 +534,7 @@ find_predecessor(struct critnib_node *__restrict n) {
             return NULL;
         }
 
-        n = n->child[nib];
+        utils_atomic_load_acquire_ptr((void **)&n->child[nib], (void **)&n);
         if (is_leaf(n)) {
             return to_leaf(n);
         }
@@ -636,7 +638,9 @@ static struct critnib_leaf *find_successor(struct critnib_node *__restrict n) {
     while (1) {
         unsigned nib;
         for (nib = 0; nib <= NIB; nib++) {
-            if (n->child[nib]) {
+            struct critnib_node *m;
+            utils_atomic_load_acquire_ptr((void **)&n->child[nib], (void **)&m);
+            if (m) {
                 break;
             }
         }
@@ -645,7 +649,7 @@ static struct critnib_leaf *find_successor(struct critnib_node *__restrict n) {
             return NULL;
         }
 
-        n = n->child[nib];
+        utils_atomic_load_acquire_ptr((void **)&n->child[nib], (void **)&n);
         if (is_leaf(n)) {
             return to_leaf(n);
         }