Use atomics in critnib find_*

bratpiorka · ldorau · commit adce85f9c05d · 2025-03-10T11:17:22.000+01:00
It fixes ThreadSanitizer data race in find_predecessor()
vs critnib_insert() and critnib_remove().

Signed-off-by: Lukasz Dorau &lt;lukasz.dorau@intel.com&gt;
diff --git a/src/critnib/critnib.c b/src/critnib/critnib.c
@@ -525,7 +525,9 @@ 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;
             }
         }
@@ -534,7 +536,7 @@ 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);
         }

Original file line number	Diff line number	Diff line change
`@@ -525,7 +525,9 @@ find_predecessor(struct critnib_node *__restrict n) {`
`525`	`525`	`while (1) {`
`526`	`526`	`int nib;`
`527`	`527`	`for (nib = NIB; nib >= 0; nib--) {`
`528`		`- if (n->child[nib]) {`
	`528`	`+ struct critnib_node *m;`
	`529`	`+ utils_atomic_load_acquire_ptr((void )&n->child[nib], (void )&m);`
	`530`	`+ if (m) {`
`529`	`531`	`break;`
`530`	`532`	`}`
`531`	`533`	`}`
`@@ -534,7 +536,7 @@ find_predecessor(struct critnib_node *__restrict n) {`
`534`	`536`	`return NULL;`
`535`	`537`	`}`
`536`	`538`
`537`		`- n = n->child[nib];`
	`539`	`+ utils_atomic_load_acquire_ptr((void )&n->child[nib], (void )&n);`
`538`	`540`	`if (is_leaf(n)) {`
`539`	`541`	`return to_leaf(n);`
`540`	`542`	`}`