timers/migration: Convert "while" loops to use "for"

Both the "do while" and "while" loops in tmigr_setup_groups() eventually
mimic the behaviour of "for" loops.

Simplify accordingly.

Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://patch.msgid.link/20251024132536.39841-2-frederic@kernel.org

Author: Frederic Weisbecker

kernel/time/timer_migration.c

@@ -1642,22 +1642,23 @@ static void tmigr_connect_child_parent(struct tmigr_group *child,
 static int tmigr_setup_groups(unsigned int cpu, unsigned int node)
 {
 	struct tmigr_group *group, *child, **stack;
-	int top = 0, err = 0, i = 0;
+	int i, top = 0, err = 0;
 	struct list_head *lvllist;
 
 	stack = kcalloc(tmigr_hierarchy_levels, sizeof(*stack), GFP_KERNEL);
 	if (!stack)
 		return -ENOMEM;
 
-	do {
+	for (i = 0; i < tmigr_hierarchy_levels; i++) {
 		group = tmigr_get_group(cpu, node, i);
 		if (IS_ERR(group)) {
 			err = PTR_ERR(group);
+			i--;
 			break;
 		}
 
 		top = i;
-		stack[i++] = group;
+		stack[i] = group;
 
 		/*
 		 * When booting only less CPUs of a system than CPUs are
@@ -1667,16 +1668,18 @@ static int tmigr_setup_groups(unsigned int cpu, unsigned int node)
 		 * be different from tmigr_hierarchy_levels, contains only a
 		 * single group.
 		 */
-		if (group->parent || list_is_singular(&tmigr_level_list[i - 1]))
+		if (group->parent || list_is_singular(&tmigr_level_list[i]))
 			break;
+	}
 
-	} while (i < tmigr_hierarchy_levels);
-
-	/* Assert single root */
-	WARN_ON_ONCE(!err && !group->parent && !list_is_singular(&tmigr_level_list[top]));
+	/* Assert single root without parent */
+	if (WARN_ON_ONCE(i >= tmigr_hierarchy_levels))
+		return -EINVAL;
+	if (WARN_ON_ONCE(!err && !group->parent && !list_is_singular(&tmigr_level_list[top])))
+		return -EINVAL;
 
-	while (i > 0) {
-		group = stack[--i];
+	for (; i >= 0; i--) {
+		group = stack[i];
 
 		if (err < 0) {
 			list_del(&group->list);