[PATCH] lib: skip percpu_counter_tree boundary kunit tests on single-CPU

[David Carlier <devnexen@gmail.com>]

On single-CPU topologies, accuracy_multiplier is zero, making both
approx_accuracy_range.under and .over zero. The boundary tests in
hpcc_test_compare_value_boundaries and hpcc_test_compare_counter_boundaries
then degenerate to comparing 0 vs 0, which correctly returns 0 (equal)
but the tests expect nonzero results.

Skip these boundary tests with kunit_skip() when accuracy is zero,
since approximation boundaries are meaningless without multi-CPU carry
propagation. Use percpu_counter_tree_items_size() as the topology check
before any allocations to avoid leaking memory on skip.

Fixes: ebc1ff504f55 ("lib: add kunit boundary tests for percpu_counter_tree comparisons")
Signed-off-by: David Carlier <devnexen@gmail.com>
---
 lib/tests/percpu_counter_tree_kunit.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/lib/tests/percpu_counter_tree_kunit.c b/lib/tests/percpu_counter_tree_kunit.c
index 4d058bc78f7d..b773d20867d4 100644
--- a/lib/tests/percpu_counter_tree_kunit.c
+++ b/lib/tests/percpu_counter_tree_kunit.c
@@ -93,6 +93,9 @@ static void hpcc_test_compare_value_boundaries(struct kunit *test)
 	unsigned long under = 0, over = 0;
 	int ret;
 
+	if (!percpu_counter_tree_items_size())
+		kunit_skip(test, "no approximation accuracy on single-CPU topology");
+
 	counter_items = kzalloc(percpu_counter_tree_items_size(), GFP_KERNEL);
 	KUNIT_ASSERT_PTR_NE(test, counter_items, NULL);
 	ret = percpu_counter_tree_init(&pct, counter_items, 32, GFP_KERNEL);
@@ -197,6 +200,9 @@ static void hpcc_test_compare_counter_boundaries(struct kunit *test)
 	unsigned long combined;
 	int ret;
 
+	if (!percpu_counter_tree_items_size())
+		kunit_skip(test, "no approximation accuracy on single-CPU topology");
+
 	counter_items = kzalloc(percpu_counter_tree_items_size() * 2,
 				GFP_KERNEL);
 	KUNIT_ASSERT_PTR_NE(test, counter_items, NULL);
-- 
2.53.0